Document jGjN3DpyJk6xOaqLgQEgX87Q

A GUIDE TO THE APPLICATION AND INSTALLATION OF LARGS BOILERS IN HYDRONIC HEATING SYSTEMS Sales Personnel Development Unit American-Standard Plumbing and Heating Division 40 West 40th Street New York l8, New York Form No. SFD-6313 July 1, 1963 Copyright 1963 American Radiator & Stan^urd Sanitary Corporation ~ * r , ' 10592 FOREWORD To the Field Sales Personnel "No salesmen ever lost an order because he knew too much about his product." This Guide has been prepared to aid field 6ales personnel in the application, installation and sale of American-Standard cast iron boilers, especially the G-hO, G-60, A-5 and A-7. Fundamentals of heat, pressure, combustion and electricity have been covered for background. In a few instances complete technical and scientific accuracy have been sacrificed in the interest of simplicity and brevity. Such omissions have no practical effect upon the understanding of funda mentals in the ranges of temperature and pressure applicable to large boilers. The technical and practical information on steam systems, hot water systems, manifolding and breeching sizing, to name a few subjects, should be helpful in guiding the contractor, the architect and the consulting engineer on boiler replacement as well as new in stallations . Certain special applications are discussed, the theory explained and tables prepared to simplify the arithmetic required for an accurate engineering approach to the problem. It is suggested that you study the Guide and use it in its pres ent tentative form. During the next year additional Chapters may be required. Perhaps som of itB present Chapters will need expanding. Whatever the action taken will depend on the Guide's usefulness to you. 10593 TABLE OF CONTENTS Chapter 1 Fundamentals of Heat " 2 Fundamentals of Pressure 3 Fundamentals of Combustion \ 4 Fundamentals of Electricity 5 Control Circuits 6 Basic Control Systems 7 Heating Control Systems -- Large Buildings 8 Cast Iron vs Steel Boilers 9 Stoker-Fired Boilers 10 Oil Fired Boilers 11 Indirect Domestic Hot Water Heaters 12 How the Steam System Works 13 Steam Accessories 14 Steam Piping Details and Terminology 15 Sizing the Piping 16 Pressure Steam Systems 17 Steam Systems -- Pressure Below Atmosphere 18 Steam Boiler Manifold Sizing 19 Hot Water -- Forced Circulation 20 Hot Water -- Sizing and Location of Pump 21 Hot Water -- Sizing the Expansion Tank 22 Hot Water -- Boiler Manifold Sizing l 23 Converters 24 Sizing the Boiler 25 Sizing -- Chimney and Breeching 10594 TABLE OF CONTENTS (Cont'd) Chapter 26 tl 27 u 28 II 29 ll 30 II 31 U 32 tl 33 Locating the Boiler Blast Coils and Unit Heaters Domestic Hot Water Greenhouse Heating Heating Swimming Pools Maintenance Competitive Comparisons Getting the Order 10595 CHAPTER 1 FUNDAMENTALS OF HEAT 10596 CHAPTER 1 FUNDAMENTALS OF HEAT Including several vays of looking at heat... how it is measured...and how it is trans ferred. We measure the intensity of heat with a thermometer. The thermometer tells "how hot" a substance is. It does not tell us how much heat the sub stance contains. Obviously two quarts of boiling water hold more heat than a cupful... but the thermometer in each case reads 212F. We measure the quantity of heat in btu'6 (British Thermal Units). This measurement is based on two factors: 1) The temperature (Fahrenheit) or intensity of the heat in a substance. 2) The weight of the substance in pounds. We can then use the btu to measure the heating power of fuels, heat losses and gains in buildings, the heat-carrying capacity of pipes, the capacity of boilers, etc. One btu is the quantity of heat needed to raise one pound of vater one degree fahrenheit. Two btu's will raise two pounds of vater one degree or one pound of water two degrees. How many btu's are required to heat 12 pounds of water at 32F to l80F? Y equals 12 (pounds of water) x 1 x (180-32) Y equals 12 x 1 x 148 Y equals 1776 btu's So far we have discussed btu's as a measurement of the quantity of heat needed to raise temperatures. Actually it is a measurement of the quantity of heat exchanged. If we take one pound of water at 70F, put it on the stove and heat it to the boiling point, we will have used 142 btu's (212-70). If we then set the one pound of boiling water on a counter, it will liberate or give off 142 btu's, as it cools back to 70F. This experiment demonstrates two things; 1) The law of heat exchange; heat lost = heat gained. 2) The fact that heat flows when there is a difference in temperature...from the warmer to the cooler substance. Page 1-1 10597 Specific Heat Different substances have different capacities for absorbing (and giving off) heat. This capacity depends upon the specific heat. Specific heat is the number of btu's required to raise one pound of the substance 1F. V.reter, in the temperature ranges encountered in low temperature hot water heating, has a specific heat of one. A cubic foot of water at atmospheric pressure and 70F weighs 62.27 lbs. This water heated to 170F absorbs 6227 btu or approximately 3460 times the heat absorption of air. This explains in part why warm air systems need large ducts as com pared with the small pipes needed in hot water systems. The State of a Substance Practically all substances can exist in more than one state. Metals are solid, or, when they are melted, liquid. If heated to a high enough temperature, they will vaporize, 'water, our main interest, also exists in three states; at a pressure of 29*92 inches of mercury it is solid, as ice, at 32F and below...liquid, as water, from 32F and through 212QF...and in a gaseous state, steam, at 212F and above. These temperature limits will change under pressure, ye'll get to that in the next chapter. Sensible Heat (or Snthalpy) and Latent Heat First; the new word, "enthalpy". The dictionary defines it as, "the sum of the Internal and the external energies of a fluid system; thermodynamic potential at constant pressure." Because we are more interested in the heat potential or the ability to heat than we are in the inherent heat of the liquid, enthalpy is a more exact definition. However, some engineers (usually the older ones) will use the word "heat" usually in the phrase "heat content" while some (usually the younger ones) will use the word "enthalpy". Despite the difference In dictionary definition, they are both talking about the same thing. Sensible heat is the heat required to change the temperature of sub stance. It gets its name from the fact that this form of heat can be sensed or felt. In measuring the sensible heat of a substance, this measurement must be made from some base temperature. With water a base temperature of 32F is used, since this temperature is the lowest at which water can exist in the liquid state under standard atmospheric pressure. The sensible heat or enthalpy of one pound of water at l80F is approximately 148 btu. Two pounds of water at l8oF would contain twice 148 btu, or approximately 296 btu of sensible heat or enthalpy. Latent heat...or enthalpy...is heat that cannot be sensed, or felt. It is heat used to change a substance from one state to another. Page 1-2 10598 Boiling water must be kept boiling by the application of heat to change it into steam. But because the temperature of both the water and the steam remain the same during boiling, this heat cannot be sensed, or felt. It is hidden or latent heat. This latent heat put into boiling the water jis then recovered, in a steam system, as the steam in the radiators condenses back into the liquid state. The quantity of heat required to change one pound of boiling water into steam (970*3 btu at atmospheric pressure) is called the "latent enthalpy of vaporization" or just "enthalpy of vaporization". Again, some older engineer may substitute the word "heat"! Steam; Saturated and Superheated During boiling, steam rises from the surface of the water at the same temperature as the water and Is called saturated steam. Its enthalpy con tent is equal to the sensible enthalpy of the water plus the latent enthalpy of evaporation. Superheated steam is steam that has been removed from the presence of the boiling water by the steam main and then put through a series of tubes called a superheater. The tubes are then heated...the steam absorbs the additional heat and becomes superheated. Additional heat cannot be applied to the steam in the presence of the water because the added heat would result only in the boiling of more water. To see the effect of heat on water, let's apply heat to one pound of water at 32F, at atmospheric pressure. FIGURE 1-1 Page 1-3 10599 Raising one pound of water from 32F to 212F requires l80 btu of sensible heat. To boil the water completely into steam requires 970.3 btu of latent heat. Because the specific heat of superheated 6team under these conditions is 0.46 only 8.64 btu of sensible heat is required. (230-212 x 1 x 0.48 8.64) Thus, the total enthalpy of the saturated steam equals: The enthalpy of the liquid -- 180.0 btu plus the enthalpy of vaporization -- 970.3 OR 1,150.3 btu And the total enthalpy of the superheated steam equals; The enthalpy of the liquid -- 180.0 btu plus the enthalpy of vaporization -- 970.3 plus the enthalpy of superheat -- 8.64 OR 1,158.94 btu These figures Eire true at atmospheric pressure only. Variations in pressure will vary the temperature at which water boils and bo, al60 vary the sensible, latent and total enthalpies. Equivalent Direct Radiation (EDR) Steam Steam heating boilers and radiation are rated in square feet of equivalent direct radiation (EDR). One EDR of steam equals 240 btu per hour. In the early days of steam heating, the old large column radiators gave off 240 btu per hour per square foot of surface, when tested with steam at 215F. Modern radiation, being much more efficient, has changed the numbers but the theory remains the same. Today's radiation is tested with steam under carefully maintained code conditions to determine its capacity in btu/hr. This figure is then divided by the old standard of 240 btu/hr. per square foot. The resultant figure i6 a rating in "square feet of radiation" (or EDR). Though it has no relation to the actual square feet of surface under test, it does provide a standard to measure the capacity of various kinds and types of radiation and boilers. Page 1-4 10600 Using EDR to Compute Relationship Between Radiation and Boiler To convert one pound of boiling water to one pound of steam at 215F requires a latent enthalpy of 968.4 btu. The steam, as it condenses in the radiator, will of course deliver 968.4 btu through the radiation to the space to be heated. Since one square foot of EDR equals 240 btu hr...4 square feet of EDR equals 9^0 btu/hr...or 4 square feet of EDR approximates the heat delivered by one pound of steam at 215F. EXAMPLE How many pounds of steam must a boiler make to carry the load of 1600 square feet of radiation? 1600 sq. ft._______ sq. ft./lb. of steam Equals 400 lbs. of steam/hr. EXAMPLE Specifications for a boiler state that it has the capacity to deliver 500 lbs. of steam per hour. What is the boiler's capacity in square feet of radiation? 500 lbs. steam/hr. x 4 6q. ft./lb. equals 2,000 sq. ft. Page 1-5 10601 CHAPTER 2 e FUNDAMENTALS OF PRESSURE I 10602 CHAPTER 2 FUNDAMENTALS OF PRESSURE "Pressure", like many words in the English language, has many variations. For instance, "moral pressure", "pressure group", "pressing", "squeezing", "weight or burden", etc. However, in this text, we are interested in the "mechanical" definition: "a force in the nature of a thrust, distributed over a surface". In discussions of boilers, piping, radiation, etc., we can precisely measure pressure by measuring both the force and the area against which it is exerted. Probably the most common expression of pressure is in "pounds per square inch"...or p.s.i. Other ways to measure and state the force of a pressure are based on the weight of water and mercury. Water: 62F Mercury: 32F Assume two tanks 12" x 12" x 12"...one filled with water, one with mercury. Figure 2-1. We also assume water temperature of 62F and mer cury temperature of 32F. These are arbitrarily chosen standards to es tablish a definite relationship between weight and volume. Heated above 32F, for instance, the mercury would expand and run over the sides of the tank. We would still have the same volume but less weight. Page 2-1 10603 Water; 62F Mercury; 32F 62.37 Its. 848.2 lba. 62.37 lbs. per sq. ft. Total Pressure at Bottom 848.2 lbs. per sq. ft. 62.37 _ i,-,. = Pressure lbs. per sq. in. 848 . 2 _ c an iw We now see that 12 inches, or one foot column of water, exerts a pressure of .433 p.sii. while one foot of mercury equals 5-89 p.s.i. By computation, then, we can set up other standards; If 1 foot of water equals .433 p.s.i., then 1 (27.72") of water = 1 p.s.i. .433 or 2.31 feet If 1 foot of mercury equals 5.89 p.s.i., then 1 1 5-89 or .17 feet (or 2.036") of mercury = 1 p.s.i. Also 5.89 p.s.i. -7- 12 will give the pressure 1 inch of mercury, .491 p.s.i. We now have four different methods of expressing or defining "pressure"; 1. Pounds per square inch 2. Inches of water 3. Feet of water 4. Inches of mercury Why four? Basically, for the same reasons that space engineers discuss the dimensions of electronic components in "tenths of an inch"...the speed of supersonic aircraft in terms of "mach"...the distance between stars in terms of "light years"...to give them more practical and manageable figures to work with. The selection of any of the four expressions for pressure is determined by the size of the force being defined. For instance, boiler pressure, when greater than the atmosphere, is a large pressure and is expressed in "pounds per square inch", while the draft in a boiler is such an extremely 6mall pressure, it is expressed in "inches of water", which, even then, usually turns out to be only a fraction. The expressions "greater than atmosphere" and "less than atmosphere" are quite common. They point to the importance of the atmosphere in pressure measurements. 1 t 1 [11 Page 2-2 10604 Atmospheric pressure is all around us. We live at the bottom of an ocean of air, which most time goes unnoticed. It seems to be a relatively light pressure, because we've grown used to it, and because it exerts equal pressure on all sides. Atmospheric pressure is often referred to as barometric pressure, be cause it is measured with a barometer. The simplest barometer is a mercury barometer -- Figure 2-2 Take a glass tube, fill it with mercury...heat it to drive off air bubbles created in the filling process...put your finger over the open end to keep the mercury from running out...bury the open end in a pool of mercury open to the atmosphere...bring the tube to a vertical position... arrange a scale so you can read the height of the mercury in the tube above the mercury in the pool ...and you have a mercury barometer. Some of the mercury will run out of the tube into the pool, leav ing a vacuum at the top of the tube. How much will run out? Just enough so as to leave the mercury in the column with weight enough to ex ert the same pressure as the pressure of the atmosphere on the surface of the pool surrounding the base of the tube. FIGURE 2-2 Because 6tormy weather i6 pre ceded by a drop in atmospheric pres sure which causes "a falling glass" and clearing weather with a rise in atmospheric pressure causing "a ris ing glass"...the barometer is a basic instrument in weather forcasting. In Figure 2-3 we 6how 29*92 inches because that is the height of the mercury column under average conditions at sea level...and represents the equivalent pressure of 14.696 p.s.i. which is the pressure of a "standard atmosphere". Page 2-3 10605 Standard Pressure - Sea Level Pressure 5,000 ft 1 Elevation 25" Hg 29.92" Hg Absolute Zero Pressure FIGURE 2-3 At higher altitudes, because the amount of air above you is less, the atmospheric pressure is less. In Denver, Colorado, for instance, under average conditions the mercury column is approximately 25 inches high. The readings in p.s.i. are ob tained by multiplying the height of the column in inches by the density of mercury (.491 lbs. per cubic inch). This chart shows an atmospheric pres sure of 1^.696 p.s.i. at sea level and 12.279 at Denver. Hg is the chemical symbol for Mercury. Both of these pressures are measurements from an absolute zero pressure line and so they are ( as are all barometric readings) abso lute pressures. Gage and Vacuum Pressure The pressures inside a heating system are limited by the design of the equipment and the temperature at which it works. They are called gage pres sures because they are measured by a gage. The most common gage is the Bourdon Tube, usually made of steel, and oval in its cross section. Pressure from the boiler, fill ing the tube, tends to straighten it out, while atmospheric pressure, pushing on the outside, tends to make it curl up. Actually, then, the tube takes a position determined by the differ ence between the boiler pressure and the atmospheric pressure. FIGURE 2-4 Page 2-4 !.i 10606 By connecting the end of the Bourdon Tube in Figure 2-5 via link age (A,) to quadrant (B), which meshes with a small pinion gear (C) mounted on a shaft which carries pointer (D), we can calibrate a scale (E) to read the gage pressure. FIGURE 2-5 In Figure 2-6 we show the indicator at zero, which means that boiler pres sure is exactly compensating for the atmospheric pressure and precisely can celling it out. We can now finish calibrating our scale both up (when boiler pressure ex ceeds atmospheric pressure) and down (when boiler pressure falls below at mospheric pressure, creating a negative pressure or vacuum). Arbitrarily, pressures above at mosphere are expressed in "pounds per square inch"...pressures below atmos phere sure expressed in "inches of mer cury." FIGURE 2-6 Boiler pressure is then added to (in the case of gage pressure) or subtracted from (in the case of vacuum pressure) the existing atmospheric pressure, to arrive at the total or "absolute pressure" affecting the system. Page 2-5 10607 Atmospheric Pressure Approx. 30" Hg or 14.7 pel Starting at sea level. Figure 2-7, with no pressure added or subtracted by the functioning of the system, it is subject only to atmospheric pres sure of 14.7 p.s.i. (rounding off 14.696), or 30 inches of mercury (rounding off 29.92). To denote gage pressure we add the letter "g" to our abbreviation If P*-6*4l< I* Absolute Zero Pressure FIGURE 2-7 Boiler Pressure______ Atmospheric Pressure Sage Pressure 5 psig r JL Vacuum 5" Hg <* > Approx. 30" Hg or 14.7 psi Absolute Pressure 25" Hg Absolute Pressure 19.7 P8i If the system then develops 5 p.s.i.g. of internal pressure. Figure 2-8, this gage pressure must be added to the atmospheric pressure to get the absolute pressure (19.7 p.s.i.) etc. If the system builds up a vacuum, or negative pressure equal to the weight of 5 inches of mercury, we will have a drop in absolute pressure from 30 inches Hg to 25 inches Hg and so on. Absolute Zero Pressure '1 FIGURE 8-8 Page 2-6 - 1 < 10608 Importance of Pressure The knowledge of these pressures and how they are determined is important since the absolute pressure on a liquid determines its boiling temperature. This phenomenon holds true whether the liquid be water. Freon or a metallic liquid such as mercury. For practical purposes particularly at elevations near sea level, boiling temperatures can be related to gage pressure. However, the atmos pheric pressure diminishes about 4$ for each 1,000 feet above sea level. Consequently, to get a reasonably accurate estimate of boiling temperatures, pressures must be corrected to absolute. Page 2-7 10609 CHAPTER 3 FUNDAMENTALS OF COMBUSTION 10610 CHAPTER 3 FUNDAMENTALS OF COMBUSTION Combustion...or burning...ie the rapid oxidation of a substance and characteristically the result is the production of heat and light. The word "oxidation" here means the combining of oxygen with another substance to form a third substance. The combustion process, when methane gas is used as a fuel, can be expressed as: CH4 + 2 Og '--> C02 + 2 H20 These symbols mean; CH^ equals 1 cu. ft. of Methane (CH^) 2 02 equals 2 cu. ft. of Oxygen (02) COg equals 1 cu. ft. of Carbon Dioxide (COg) 2 H20 equals 2 cu. ft. of water (E^O) So the equation now reads, "Combine one cubic foot of methane with 2 cubic feet of oxygen and the resultant combustion will leave one cubic foot of carbon dioxide and 2 cubic feet of water (in the form of steam) as flue gases. Because the only practical way to get the oxygen is from the air around ub, and because oxygen is only 21$ of air by volume, we must, in theory, introduce 4-3/4 cubic feet of air into the system for every cubic foot of oxygen required, or 9-1/2 cubic feet of air to supply the 2 cubic feet of oxygen called for in our equation. The other 79$ of the air is assumed to be nitrogen. The left hand side of the equation now reads; CH4 9*5 Air But because we are primarily interested in the 2 cubic feet of oxygen, we separate it and the 7.5 cubic feet of nitrogen and write the equation this way; CH^ + 2 02 + 7.5 N2 --> COg + 2 HgO 7*5 N2 Page 3-1 10611 Now the formula says that when 1 cubic foot of methane (CH^) is burned with 9-5 cubic feet of air the resultant flue gases are 1 cubic foot of CC^, 2 cubic feet of steam and 75 cubic feet of nitrogen. The nitrogen does not Join in the combustion process, but is heated along with the C02 and the HgO. The heat that these products carry off is called stack loss. The above formula represents perfect or theoretical, combustion. As a practical matter, theoretical perfection is impossible to attain. Therefore, in order to insure that every molecule of Methane is furnished the proper number of molecules of oxygen, excess air is introduced into the system to furnish additional oxygen. With natural draft gas burners, approximately 50$ excess air is added. Since the excess air, representing a safety factor, is not used up in the combustion process, it is added to the flue gases...and increases the stack losses. That's why 50$ excess air is used, not more. Obviously 70$ excess air would contain even more oxygen and represent an even greater safety factor. But it would also represent extra gases to absorb more heat and create a higher chimney loss. Adding surplus gases of any kind to the combustion products loses heat two ways; 1. In Just heating more flue gases 2. All boilers have flues to hold the hot gases in the boiler so that the water jacket can absorb more of their heat before they are vented. As the quantity of flue gases increase the velocityof the gases through the flues increases. The gase6 moving through the flues faster have less time to give up their heat to the boiler surface and consequently go up the chimney at higher tem peratures, thus increasing the stack loss. Stack temperatures from a given boiler have a direct relationship with the amount of flue gases going through it. Now, let's look at our formula for perfect burning again, CH^ 2 02 + 7-5 N2 C02 + 2 H20 + 7-5 N2 and add the 50$ air for complete practical burning. C\ + 3 02 11.25 N2 C02 + 2 H20 + 11.25 N2 + 02 New we have 15.25 cubic feet of flue gas. Page 3-2 it 10612 If a CO2 analysis was made on the products of combustion for perfect combustion conditions, this analysis would show 11.8$ CO2 by volume. See the following tabulation; Perfect Combustion C02 1.0 cu. ft $ by Volume 11.ti* (Steam) H20 2.0 cu. ft 0 0 n2 7.5 cu. ft 2 cu. ft TOTAL 10.5 cu. ft Less H20 2.0 88.2$ Total Dry products of Combustion. . . ., 8.5 cu. ft 100.0$ NOTE; When flue gas analyses are made, the steam condenses making it impossible to obtain its volume. Similarly the percentage of CO2 by volume analysis for practical or complete combustion of this gas becomes 7*5$ as shown in the following tabulation; Practical or Complete Combustion co2 1.0 cu. ft. (Steam) h2o 2.0 cu. ft. n2 11.25 cu. ft. 2 1.0 cu. ft. TOTAL 15.25 Less H20 2.0 $ by Volume 7.55$ 84.90 7-55 _______ Total Dry products of Combustion.......13.25 cu. ft. 100.0$ NOTE; When flue gas analyses are made, the 6team condenses making it impossible to obtain its volume. It Is evident that as the percentage of C02 in the flue gases diminishes when burning a given fuel, the amount of excess air is in creasing. Hence, the C02 percentage becomes a measure of the amount of excess air and, when combined in a formula or with curves of stack tem perature gives a basis for determining the boiler efficiency. Page 3-3 10613 When analyzing flue gases the percentage of CO2 which is obtainable under practical or complete combustion conditions varies with the kind of fuel due to the different percentages of carbon in these fuels. As the carbon content becomes larger so does the per cent of CO2. The type of fuel burning equipment plays a part. For natural gas, CO2 readings for practical combustion conditions may range from 8$ to 10$, for oil 9$ to 11$ and for coal (stoker fired) 12$ to 13$. It has been pointed out earlier in this chapter that complete com bustion of all the oxidizable elements in the fuel is desirable. To accomplish this complete combustion excess air mu6t be added. When fuel is not burned completely, heat is lost. Should insufficient air cause the carbon in the fuel to burn to carbon monoxide (CO) not only is a poisonous gas formed but only 5,500 btu per pound of carbon are released. One pound of carbon burning to C0^ releases 1^,600 btu. A similar result occurs with the hydrogen in the fuel. If sufficient oxygen is present to burn one pound of hydrogen to water vapor, 62,000 btu are released. When insufficient air is present to burn al l the hydrogen, the unburned percentage escapes up the chimney and a proportionate amount of heat is lost. The burning of oil efficiently presents a greater problem than burning the other two fuels. First the oil must be atomized into very small droplets. This is done by the nozzle. Secondly, the oil droplets must be vaporized. This action is accomplished by the combustion chamber walls. The air which is mixed with the vaporized oil now is able to burn it. Materials used in combustion chambers vary from stainless steel and light-weight refractory materials to fire brick. Dense fire brick is usually employed where oil is being burned continuously. Intermittent firing such as practiced with American-Standard boilers requires light-weight materials for combustion chambers. The quicker the combustion chamber walls become incandescent^ following the starting of the burner, the quicker the combustion conditions reach maximum efficiency. Page 3-^ 10614 LflM ncn FUNDAMENTALS OF ELECTRICITY * 10615 CHARTER 4 FPmAMEmALS OF ELECTRICITY An electric current is formed, by the movement of electrons. Because electrons move easily in metals; silver, copper, aluminum, etc., they are used to "conduct" electricity from source to load. Because electrons do not move easily in such materials as glass, porcelain, cotton and rubber, they are used as insulation. The flow of electric current in a circuit is analagous to the flow of water in a piping system. The pressure or force making the current flow is supplied by a gen erator or a battery. Wire size and length of the circuit determine the quantity of electri city flowing. Large wires have less resistance to current flow than grnali ones. The terminolpgy in electricity is as follows; 1. The pressure or electromotive force (EMF) is measured in volts. 2. The quantity of electricity flowing is measured in amperes. 3. A rate of flow can be expressed as ampere hours. 4. Power equals volts X ampere hours divided by hours or watts. A German physicist, George Simon Ohm, first studied electricity flow in a circuity in 1822. He found that in every circuit the amount of current is dirctly proportional to the pressure, or EMF, applied, and inversely proportional to the resistance in the circuit...of I =-- R The formula, I ='--EA , is called Ohm's law. Resistance varies from circuit to circuit for three reasons. 1. Various conductors have different resistances. Silver is the best conductor and copper is almost as good (and a lot cheaper). Aluminum offers greater resistance, but because of its weight, is often used for large overhead cables. 2. The length of the circuit. The longer the wire, the greater the resistance. 3 The thickness of the conductor. The thinner the wire the greater the resistance. Page 4-1 10616 A convenient way to remember Ohm's law. Cover what you're look ing for and the re6t of the diagram will tell you the formula. To find amps...cover amps in the diagram and the formula then is -2.. Similarly R isCovering volte leaves I x R. FIGURE 4-1 One other important formula for measuring electricity and its effects is the relationship between E (volts)., current (amperes) and power de livered (watts); Watts equals Amperes X Volts A 60-watt bulb connected to a 110-volt supply uses; 60 - A X 110 or 60 : .55 amps 110 A toaster using 11.5 amps in a 110-volt supply uses; W = 11.5 x 110 or 1265 watts Electricity is either DC (direct current) or AC (alternating current). In direct current the electrons move around the circuit always in the same direction. In the alternating current circuit, they move in one direction for a time, then reverse themselves and move in the opposite direction. This is similar.to the action of a piston in a cylinder of your automobile engine. And, as with the piston in a cylinder, one move in both directions is called a cycle. The standard in this country is 60 cycles per second, though there are some variations. Before installing any piece of electrical equip ment it is very important to know the AC cycle time as well as the voltage and amperage available. The generation of electric current is a relatively simple principle. If a wire in a circuit is moved through a magnetic field an electric current will be produced in the wire. - . r, I Page 4-2 10617 FIGURE 4-2 FIGURE 4-3 FIGURE 4-4 With the north and south poles of a magnet facing each other, a mag netic field is set up between them. A wire connected to a circuit at posi tion "A" would have no voltage generated and no current flowing through it. As the wire is moved through the magnetic field, however, voltage is created and the current starts to flow and reaches its maximum value in loth volts and amperes at point "B" whf. re the magnetic field reaches it maximum density. As the wire continues to move toward "C" the voltage and current will lessen again, until at "C", it once amain reaches zero. .Rage 4-3 10618 When the wire i6 then moved hack through the magnetic field, voltage and current will again reach maximum value at point "B". Only, this time, because of the reversed movement, the voltage and current will be in the opposite direction. Continuing back toward "A", the voltage and current will, again, lessen and, again reach zero at '^"...com pleting one cycle in the generation of AC current. The amount of current depends on the strength of the magnetic field, and the size of the wire. Obviously, if the circuit included a bulb, and the frequency of cycling was very low, the bulb would flicker. At 60 cycles per second the alternate build-up and fall-off of current have no apparent effects on the continuity of light given off by an electric bulb, since it does not have time to cool down. Motors are roughly similar to generators. The difference is that with a generator, mechanical energy i6 used to tUm the coil which makes it turn and deliver mechanical energy. The same effect of alternating current can be accomplished by holding the wire stationary and moving the magnet. t ' [<' Page 4-4 10619 5-f*TOR Co,c To generate large amounts of power, huge electromagnets are rotated In the center of a series of coils. As the poles of the magnet spin, their magnetic fields rotate and in duce current in the coils. FIGURE 4-7 The frequency is determined by the number of magnets and the speed with which the magnets turn...the amount of current generated is determined by the power of the magnet and the dimensions of the wire in the coils. To obtain the 6ixty cycle current commonly in use in thi6 country generators operate as follows; with 2 pole magnet 4 pole magnet 6 pole magnet 3600 r.p.m. 1800 r.p.m. 1200 r.p.m. The above listed r.p.m.'B axe known as synchronous speeds. Induction motors try to attain the same synchronous speeds depending on the number of poles they have. For example an induction motor rated at 1750 r.p.m. is designed with 4 pole6. The motor load, slows it down to the rated speed. Similarly a 3450 r.p.m. induction motor is of two pole design. Another use of the electromagnet is to keep the magnet stationary and move the magnetic flux inside the magnet. This is the principle used in the transformer. Page 4-5 10620 FIGURE 4-8 FIGURE 4-9 When a coil around a magnet is connected to an AC source, magnetic flux is built up in, and travels around, the magnet. Thi6 flux movement corresponds to the AC cur rent building up and then falling off... first in one direction and then the other If we then wrap another, secon dary coil around the magnet, the magnetic flux moving in the magnet will "induce" a current in this secondary coil. The important features of this transformer are based on the fact that the relationship of voltage between the primary coil "A" and secondary coil "B" are determined by the number of turns in each coll. The cycles in the secondary coil will be the same as in the primary. Page 4-6 'i t 10621 If the primary coil had double the turns of the secondary, we would have a step-down transformer and the result would be reversed; Voltage would be cut in half, and the amperage doubled. Example; In a 115/24 volt step-down transformer the primary coil has 230 turns. How many turns in the secondary coil? No. of turns * 230 X 24 115 or 48 turns The transformer allows us to alter available voltage to suit the needs of various pieces of equipment. The first and most important use of transformers, however, is to make it possible to transmit large amounts of electrical power over long distances, economically. Large amperages need large diameter wires. But, because with a trans former with many turns on the secondary and relatively few on the primary we can build up the voltage, and at the same time reduce the amperage by very large amounts, power can be transmitted by relatively light, inexpensive cable. Long-Distance transmission voltages often exceed 300*000 volts. Sub-stations may transform this voltage to something like 12,000 volts for short transmission systems with secondary sub-stations stepping it down even further to 2400 volts. The 2400 volts, then, on its way to the consumer (residential, com mercial or Industrial) is finally reduced by the transformer on the utility pole to 4-4-0, 230, 208, or 115 volts depending on need. 3 fha** * 2100 Tolt s' Dlrtrlbvtlan 3ln<tUflii*to- Sa lnAafli*itoHiumm 230 volt* If your home has a 3-wire elec tric service offering you both 115 volts and 230 volts, this diagram shows the circuits from utility pole to the house. FIGURE 4-10 Page 4-7 10622 The two wires at either end of the secondary coil are brought into the house. These are both hot wires and may carry a 230 volt current between them. A third wire tapped into the center of the coil is brought into the house, but is also brought down the pole and grounded. This third wire, then, is neutral and carries 115 volts between it and either hot wire. This gives us 230 volts across the two hot wires for 230 volt ap pliances like stoves and hot water heaters, for instance. Also there are 115 volts for lighting and 115 volt appliances like toasters, radios, etc., between the ground wire and either hot wire. This set-up is called a three-wire, single phase service. The three wire, single phase circuit provides greater flexibility of service, ease of installation with simple switching on the 115 volt side and safety. For example, a light circuit in the house is 6hown in Figure 4-11. Note that by throwing the switch in the hot line it is safe to make repairs on the light socket since the other connection is already grounded. Fuse_^ Q Box H G H Toggle Switch FIGURE 4-11 The same safety principles are applied for -115 volt circuits at the fu6e box. When 230 volts are involved with both wires hot, a double pole switch must be used to isolate both sides of the circuit. For an additional understanding of alternating current problems, the term Power Factor is important. Power Factor = true watts apparent watts OJt Power Factor Page 4-8 10623 In electric resistance circuits such as lights, toasters and resistance electric heating the power P uaed equals El. Therefore, for this type of equipment the Power Factor = -gjr = 1.0. In other words, the wattage measured by the electronic meter equals exactly the volts x amperes furnished the user by the utility company. Electric motors are a different story. The power measured by the electric meter on a motor circuit is often less than the product of volts times amperes that are supplied by the utility and the resulting power factor becomes a fraction. This condition is undesirable from the utility viewpoint. The utility is paid on the basis of power used but it must design its equipment, and size its circuits on the larger product of volts times amperes. Where large quantities of power are involved, the utility usually makes an additional charge above the meter reading when power factor conditions exist. Some Electrical Circuit Symbols designed to make or break both sides of the same circuit at the same time, when neither side is grounded and they are both hot. FIGURE 4-12 A single-pole, double-throw designed to make either one circuit or another or to break both of them FIGURE 4-13 The symbol used to indicate a ground line. FIGURE 4-14 -VWNAr Resistors, used to reduce current flow. FIGURE 4-15 Page 4-9 10624 ..-Vv\VWWvVA t FIGURE 4-l6 Tron^forme^ Primary i S (ime *a?oge) o jo Secondary (lo* votfoge) .Core " Icx^notfOns FIGURE 4-17 Tronsformef --ai;;(r Primory 1 (i.ne vatoge) 3 Secondary (low wo(toge) I (Xninotions FIGURE 4-l8 Variable resistor...or rheostat... allows the voltage to be varied between zero and line voltage. An iron core transformer. Iron core transformer with midtap giving us two different voltages. Page 4-10 10625 w* m i i cK CONTROL CIRCUITS 10626 CHAPTER 5 CONTROL CIRCUITS There are two kinds of controls used in conjunction with big boilers.- (1) Operating Controls (2) Safety Controls In the early heating systems "tending the furnace" was a common phrase. It was operated almost completely by hand and watched often. The growth and refinement of controls has been and continues to be a steady, consistent process. For instance, American-Standard electronic controls, optional equipment with our large gas-fired boilers, are one of the latest control systems to be devised. But even they will continue to be researched, developed and refined. Before we get to the actual controls, this chapter will discuss the four basic ways controls operate. (1) Electrically (2) Mechanically (3) Pneumatically (4) Any combination of these three An Electrical Heating Control Circuit Thermostat Switch 115V Transformer Source Gas Valve Load Electrical control circuits always contain a source, a switch and a load. They can be high voltage (115-230V), low voltage (20-24-V) or, in more complex controls, a combination. The control circuit shown is a low voltage circuit controlling the main valve in a gas fired boiler. FIGURE 5-1 yhile it is hooked into the main 115 volt line, it incorporates a 115/24 volt 6tep-down transformer which is the usual voltage for the load -- a solenoid coil in ghe gas valve. * (x 1 Page 5-1 10627 In thl6 ca6e, the transformer and not the main line is considered to be the source. When the switch closes a current flows through the small solenoid coil. The coil then actuates a valve mechanism causing the gas above the diaphragm of the main gas valve to be vented. The line pressure of the gas under the diaphragm will force it upward opening the main valve and permitting the gas to flow to the burners. The switch is a thermostat which is an example of a mechanical control. Before we discuss it, points should be made about the circuit in Figure 5-1. (1) This is the simplest kind of control circuit. (2) It is an operating control only. It needs, as a safety device, other switches which will be discussed in Chapter 6. (3) It shows only one of several kinds of valves, which will be covered in future chapters. A Mechanical Heating Control Circuit Thermostats, which act as switches in heating systems, by mechanical movements, make or break electric circuits. A Steel Brass iI l) The simplest thermostat is a bimetal strip...two different metals welded together, usually brass or copper in conjunction with steel. Because both copper and brass have a larger coefficient of expansion -and contraction -- than steel, a rise in temperature will cause the bimetal strip to bend in direction of arrow A. A drop in temperature makes it bend in the direction of arrow B. FIGURE 5-2 A C FIGURE 5-3 Two Wire Thermostat One end of the straight bimetal strip is fastened rigidly to a base leaving the other end free to warp under tem perature change. Also one wire is con nected to the bimetal at the base and a contact button (A) fastened to the free moving end. The second wire to the thermostat is connected to the fixed contact (b). Wired into the circuit at the base of the thermostat is a small electric heater (c). As the room temperature approaches the control point -- say J2 F -- the Page p-2 -\0628 bimetal varps toward the fixed contact (B). As the contact points (A) and (B) approach each other, magnet (D) exerts a pull on the bimetal causing a positive contact of the points, thus completing the circuit and causing cur rent to flow. In the first thermostats there were no magnets or heaters. With the light bimetal elements employed to get sensitivity the contact points did not close or open with a positive motion. Slight vibrations in the struc ture would make the contacts chatter creating an electric arcing condition. This arcing causes pitting of the points. Under severe conditions the points may fuse together or freeze. Modern thermostat design retains the light bimetal element but intro duces the magnet to insure positive closing of the contacts. It then was found that an approximate 3F rise in room temperature vould be required for the bimetal to develop enough warping force to overcome the magnet and open the contacts. Since a 3F swing in room temperature is not com fortable the additional temperature was created artifically under the thermostat cover by the heating element. The thermostat closes its contacts and completes the electric circuit under room temperature conditions, but opens the circuit under an artificial temperature created under the thermostat cover. When the thermostat closes its contacts and completes the electric circuit the thermostat heater is activated. Thus the thermostat closes under room temperature conditions but opens under an artificial tempera ture condition under the cover. With this arrangement a variation of room temperature from 0.5 F above the control point is achieved which is en tirely satisfactory for human comfort. The heater in the two wire thermostat presents a problem. It must be matched to the current draw of the load. An improperly sized heater causes improper control of room temperature. Too high an amperage through the heater causes the thermostat to open too quickly preventing the room from reaching the desired temperature. Too low an amperage through the heater slows the build-up of temperature under the cover, delays the opening of the contacts and causes the room to overheat. The three wire thermostat was designed which put the heater cir cuit in parallel with the load cir cuit thus making the heater perform ance independent of the amperage draw of the load. Figure 5-^ shows how the current flowing through the heater -circuit A -- returns to the transformer without passing through the load, per mitting all thermostats to be furnished with the same heater. Heating installers had difficulty in understanding the three wire principal and thermostats were wired improperly. Consequently, the two' wire thermostat is one commonly used today. FIGURE 5-^ Page 5-3 10629 The action of the bimetal element, alone, is a mechanical circuit, vhere physical movement is U6ed to make or break an electrical circuit. The total circuit i6, of course, a combination of mechanical and elec trical circuits. A Pneumatic Heating Control Circuit This diagram represents a pneu matic arrangement for handling the function of the main thermostat. Boa ala This circuit combines mechanical and pneumatic circuits. The familiar bimetal 6trip (A) is again used as the temperature-sensitive switch to make or break the circuit. Because this time it is a circuit 6f air rather than an electrical circuit we call the switch a valve, and the contact is a pad rather than an electrical contact. FIGURE 5-5 Air from a compressor flows through the main which has an inner orifice (B), with the same air capacity as the nozzle (C) opposite the pad on the bimetal strip. Air flow is constant, and with the switch in the open position, opening (C) will vent to the atmosphere all the air passed by orifice (B), thU6 preventing the build-up of pressure in bellows (D). The bellows i6 also held closed by the tension of spring (F). However, when the space cools, the bimetal element will warp to the left, the pad will cover opening (c) and air coming through orifice (B) builds-up pressure in the bellows (D), overcomes the resistance of the spring and moves the plunger (E) which opens a valve. Page 5-^ 10630 BASIC CONTROL SYSTEMS CHAPTER 6 BASIC CONTROL SYSTEMS The modern boiler is almost completely automatic. It has a full set of both operating and safety controls -- all meshed together in a "control system." These systems did not suddenly appear, full blown. They grew and developed; operating controls out of necessity for supplying customer com fort and convenience and safety controls out of the need for protecting equipment and property. We have already seen bow the thermostat operated by the room tempera ture can, through a combination electro-mechanical system, operates a gas valve to start and stop fuel flow. This same principle can be used to operate other kinds of valves or switches. Later in thi6 chapter we will discuss the valve6 used with American-Standard boilers. We can now start and stop fuel flow. Some way to ignite the fuel is needed. For gas a pilot light is used. Gas may be supplied to the pilot through a small line tapped off the gas main. Pilot lights sure quite dependable. But they may go out for a variety of reasons. So, a safety device is required to prevent gas being turned on in the main burner when the pilot light is out. The safety device used today on pilots is the thermocouple. It is constructed by Joining two dissimilar metals -- for example, two wires -- at the ends only. In between the two junction points the wires are insulated. See Figure 6-1. Ammeter FIGURE 6-1 Page 6-1 10632 When one junction of the circuit is heated and the other cooled, a voltage difference is created between the two Junctions and an electrical current flows. The greater the temperature difference, the greater the voltage. This same electrical system, when a direct current from an external source is passed through it, will cause cooling of one junction and heating of the other. This phenomenon is called the Peltier Effect. It may be used to create refrigeration. Some small capacity refrigeration units have been constructed. Unfortunately, efficiencies are too low at present to permit using this principle except in very special applications. The most common application of the thermocouple is the measurement of temperature. By measuring the voltage generated, or in a circuit of a fixed length and resistance by measuring the current flow, (the tempera ture difference between the hot and cold junctions) may be determined. Knowing the temperature of the cold Junction, the temperature of the hot junction , may be accurately determined. We use the thermocouple in a pilot flame to generate the necessary electrical current to hold open the Baso Valve located in the main burner manifold. Failure of the pilot flame and the cooling of the thermocouple cuases the Baso Valve to close preventing the gas from reaching the main gas valve. See Figures 6-2. OPENED POSITION FIGURES 6-2 The principle is also applied to the Baso Switch located in the electrical circuit between the thermostat and the main gas valve. The Baso Switch is held in a normally closed position by the current from the thermocouple. Failure of the pilot flame and the loss of electrical energy from the thermocouple will cause the switch to open thus preventing the main gaB valve from opening. Page 6-2 10633 Another safety problem is created when a thermostat, affected by a steady stream of cold air from an open door or similar condition, causes the boiler burner to stay on. This continuous burner operation, if permitted to continue, would cause the water in the water boiler to become too hot or excessive pres sure in the steam boiler. The answer is another switch in the electrical circuit to the gas valve. This switch is normally closed. It is the high limit. In water boilers the high limit is an immersion control. When the water temperature rises above the control setting the switch opens and stops the burner. In a steam boiler the switch is actuated by a spring loaded bellows or diaphragm which in turn is moved by the steam pressure to shut off the burner. The thermal element in the immersion control may be a bimetal helix or a bulb charged with a temperature-responsive solid or liquid. When high limits are installed on the external surface of the boiler a light weight metal disc, which changes 6hape when heated, is used. Another control used on boilers in which a minimum water temperature is required, is the operating immersion control sometimes called the "lowlimit." Its function is to operate the burner when the water temperature falls below the desired level. Still another is the reverse acting immersion control. It is called reverse acting because the switch opens with a drop in water temperature. This action is opposite to that of the immersion controls described pre viously. Its application is; 1. In a water boiler with a tankless heater. It is located in the boiler so that it feels the drop in boiler water temperature when domestic hot water is being drawn from the tankless heater. It stops the circulator and the delivery of heat to the house while the domestic hot water demand is being satisfied. Since the demands for domestic hot water are of 6hort duration this action has no noticeable effect on the house temperature. 2. When installed in boilers without tankless heaters the control may be set to operate at about 100 degrees F. It then stops the circulator when the boiler water temperature i6 approximately 100 degrees F. or less. This action prevents any tendency toward moisture condensation in the boiler flues and automatically 6tops the pump during the non-heating months. Page 6-3 10634 Another control frequently U6ed in hydronic heating systems is the relay. Its putpose is to tie together a low voltage (24 volts) control circuit with high voltage (115 volts) circuit. See Figure 6-3 115 Volts Thermostat Transformer High Limit 24 Volts Relay \ \ < Oil 1 Burner I 1 l Circulator FIGURE 6-3 Because low voltage thermostats are inherently more sensitive and low voltage wiring does not require a licensed electrician most thermo stat circuits are 2k volts. The oil burner motor is for use with 115 volts. To start the oil burner when the house needs heat requires the simplified diagram shown. When the thermostat closes, solenoid coil A i6 activated creating a magnetic pull on the switch B closing the switch points and completing the 115 volt circuit. When the thermostat is satisfied, the 24 volt circuit is de-activated, the contact arm B falls away and the oil burner stops. By connecting a circulator to the 115 volt circuit as shown by the dotted lines the same relay would activate the circulator. When selecting a relay in the field, always its capacity should be checked to determine if the amperage capacity is equal to or greater than the connected load. Separate controls and their functions have been discussed. Present trends in the industry are to combine two or more of the immersion con trols into a single package, which performs the individual functions, using one thermal element. For example, with the G-2 or G-40 water boiler operating with a tankless heater, a combination control i6 supplied that combines the high limit control, the operating control (low limit) and the reverse acting control. In addition this control includes a built-in transformer and rel^y. This combining of more than one control function into a single control package has a number of advantages. It permits a more advan tageous location of the control in the boiler and eliminates the need Page 6-4 I r>' 10635 for additional tapping6 thereby simplifying boiler and Jacket design. Con trol wiring is made easier and boiler appearance is improved. The same principles are used in controlling oil-fired boilers. The difference in fuels, however, requires a different kind of ignition and a different safety circuit. When heat is required in an oil fired boiler, oil i6 forced through a small hole in the nozzle of the oil burner. This action atomizes the oil creating a mist of very tiny droplets. At the same time a high voltage,impressed on the electrodes, creates an arc. The arc passing through the oil mist ignites the fuel. FIGURE 6-4 If the oil should not ignite, the burner must be stopped to prevent a possible explosion. This safety control may be one of two devices. The stack switch with a bimetal helix has been used in this safety role for a long time. As soon as the oil starts to burn, the flue gas temperature starts to rise. A 100 degrees F increase in stack tempera ture tells this control that the oil is now burning and that the oil burner may continue to operate until the demand for heat has been satis fied. If, after about 90 seconds of oil burner operation there is less them 100 F of increase in stack temperature, the stack switch 6tops the oil burner. A more recent safety control used with oil burners is the light sensing cell. This cell or flame detector tells the primary controller that the oil spray has ignited. The primary controller then permits the oil burner to operate until the demand for heat is satisfied. Should the oil not ignite after 45 seconds of oil burner operation, no signal is received from the flame detector and the primary controller stops the burner. The flame detector is a cell that is sensitive to the oil flame color only. It is located- at the back of the burner blast tube and pointed at the flame. The cell acts as a switch. It permits an elec trical current to pass through it when the oil is burning. This cur rent tells the primary control that Ignition has been established. Page 6-5 10636 Ignition of the oil may be continuous or intermittent. With continuous ignition the electric arc operates as long as the burner operates. In intermittent ignition the arc operates until the oil flame has been established. In case of Ignition failure, the stack switch will stop the oil burner. It must be manually reset. A drop in line voltage will cause the stack switch to stop the oil burner. Automatic re-cycling of the oil burner will occur when line voltage is restored. When ignition fails, the primary control used with the flame sensing cell also stops the burner. It must be manually reset. Similar to the stack switch the primary control stops the burner when the line voltage drops to 90 volts or less. On full power resumption the burner automatically re-cycles. Electronic boiler controls have enjoyed increased application in recent years particularly on large gas boiler installations. They have greater sensitivity, fast action and a high degree of reliability. These electronic controls are required on both the G-kO and the G-60 boilers when specifications call for the requirements of either the Factory Mutual Association (F. M.) or the Factory Insurance Association (F. I. A.). Factory Mutual Association (F. M.) The electronic control system specifically designed for the Factory Mutual Association requires electric ignition on all pilots (auxiliary and safety) and electronic control of all safety pilots. All pilots must have 100^ shut off. A protector relay is necessary for each combustion chamber. The American-Standard EG-0 or the DPG-0 control packages meet these requirements. In addition to the electronic controls F. M. requires the following valves on each gas manifold. See Figure 5-6. 1. Two manual shut off valves. 2. One gas pressure regulator. 3. One vent cook inserted in a special pipe nipple tapped l/8 inch. 4. One General Controls line voltage H-0 Hydromotor Valve with iron body and bronze trim. Normally closed. Factory Insurance Association (F. I. A.) The Factory Insurance Association specifies the same electronic con trols (EG-0 or EPG-0) as Factory Mutual. In addition F. I. A. requires the following valves and switches on each gas manifold. See Figure 5-7 1. Two manual shut off valves. 'i t . r,i Page 6-6 10637 2. One line voltage mercoid type PR high pressure semi-automatic switch set to open automatically at a pressure of 5" of water column. It must be manually reset. The pressure range of the switch i6 1" to 30" water column pressure. 3. One line voltage mercoid type PRL-3 low pressure semi-automatic switch set to open when the manifold pressure drops to 2" of water column pressure. Manual reset is required. The pressure range of the switch i6 1" to 30" water column pressure. 4. One line voltage General Controls H-0 Hydromotor valve with iron body and bronze trim. NOTE; Both the K-3E 621 solenoid and the H-0 valves are normally closed. They open on the electrical impulse received from the American-Standard pre-wired panel or the MG 890 E relay. This action occurs only after all pilots have been ignited. 5. One line voltage General Controls 3A inch iron pipe size vent valve No. K-10 CA 41+3. This valve is normally open when the solenoid (K-3S) and the H-0 valve is closed. The vent valve closes when these two valves open. Details of the General Controls valves are to be found in General Controls literature. H-0 Valve K-3 Valve K-10 Valve Form No. SDI-H-OV-1 Form No. SDI-K-3-9 Form No. SDI-K-10-4 For the electronic controls details see Electronic Control Systems for G-40 and G-60 boilers, Form No. BP-15095* Revised 12-62. The foregoing lists and arrangements satisfy the national requirements of both the Factory Mutual Association and the Factory Insurance Association. Local inspectors may request changes at times in the control equipment, and the order in which the components are installed on the gas supply piping. Page 6-7 10638 FIGURE 6-5 CONTROL ARRANGEMENT FACTORY MUTUAL APPROVED G -4 0 AND G -60 GAS BOILERS v I f, Page 6-8 10639 CONTROL ARRANGEMENT FACTORY INSURANCE ASSOCIATION FIGURE 6-6 Page 6-9 10640 HEATING CONTROL SYSTEMSLARGE BUILDINGS CHAPTER 7 10641 t CHAPTER 7 HEATING CONTROL SYSTEMS -- LARGS BUILDINGS The control of large heating systems involve the same principles as the control of small systems. However, "because budgets are larger and savings on larger amounts of fuel become important, more expensive control systems are normally Justified. Instead of the "off-on" control system, continuous but modulated heating i6 frequently employed. The pneumatic control system as briefly described in Chapter 5 is of the modulating type. Selection of radiation should be coordinated with the type of heating control. Non-ferrous finned radiation works best with continuous but modu lated heat delivery. Cast iron works equally as well with modulated heat input, buz is preferred in Intermittently heated space because of its heat holding characteristics. This chapter will discuss the control of both hot water and steam systems, single zone and multiple zone...continuous and intermittent heat delivery. Hot Water...Intermittent...Single Zone The boiler is operated at a fixed water temperature to provide domestic hot water with an immersion control in the boiler water controlling the burner. Heat is delivered intermittently when the space thermostat starts the circulator. Hot Water...Intermittent...Multiple Zone The boiler is operated the same as in a single zone system. Heat delivery to each zone may be accomplished as follows; 1. Each zone is served by a separate circulator under the control of the zone thermostat. With this type of control the circuit to each zone has a lift check valve installed to prevent a cir culator on one zone creating water circulation in a zone not calling for heat. 2. A single pump can be used for all zones with each zone having a motorized valve under the control of the zone thermostat. On large systems with heavy circulators a by-pass is usually provided between the supply and return mains to permit water circulation through the boiler and circulator when all zone valves axe closed. Water flow through the by-pass may be controlled by a throttling hand valve or by a pressure opera ted valve, which opens automatically with the rise in pump head occurring as the system water flow diminishes. Page 7-1 10642 Hot Water...Continuous...Single Zone The boiler is operated at a fixed water temperature to provide domestic hot water. An Immersion control operates the burner. Continuous heat delivery to the 6pace is achieved by operating the circulator continuously. A by-pass around the boiler with a three-way mixing valve automatically modulates water temperatures with the severity of the weather. An outdoor bulb controls the three-way valve. The circulator is controlled by an indoor thermostat set two or three degrees higher than the normal indoor temperature maintained by the outdoor control. Should indoor temperatures, for any reason, rise above the normal control point the thermostat stops the circulator and all heat delivery to the space. Hot Water...Continuous...Multiple Zone The boiler is operated the same as in the single zone system. Three-way automatically controlled mixing valves modulate the water temperature to each zone under the control of an outdoor bulb located to reflect the heat loss of the zone. A single circulator for the system or individual circulators for each zone may be used. When zones require no heat it is possible to provide auxiliary switches on the three-way valves to stop the circulator. On large hot water systems with multiple zones, piping may be designed for using a secondary pumping arrangement. Steam...Intermittent..Single Zone There are two basic control arrangements. The first is simple, inexpensive but somewhat slow in response. The space thermostat operates the burner. Steam pressure is developed to force air from the system and steam into the radiation. A variation to this method is to use an outdoor thermostat. Here the occupants of the space have no control of space temperature. The second method requires the maintenance of 6team pressure during the heating season. A combination low limit and high limit pressure-6tat is employed. The space thermostat operates a motorized valve. This is a more expensive control arrangement but the response to a call for heat is quicker. An outdoor thermostat may be used with the motorized valve. Page 7-2 f|< 10643 Steam...Intermittent...Multi-Zone In the multi-zone steam system the boiler operates at a fixed pressure with Intermittent heat delivery to each zone controlled by motorized valves operated by zone thermostats, either in the space or outdoors. In large two pipe systems each piece of radiation may have orifices installed to provide for uniform steam delivery to each radiator. Staam...Continuous...Single Zone In large house and small commercial installations, single zone steam systems accomplish continuous heat input by operating as a vapor system. With thi6 type of system, steam is maintained continuously in the radiation but under a vacuum that varies with the weather conditions. As the vacuum becomes greater, the steam temperature becomes less and the heat output from the radiation diminishes. When the space cool6, the thermostat starts the burner, increases the pressure and steam temperature -- vacuum becomes less -- and more heat is obtained from the radiation. The normal range of steam temperatures in the vapor system is from 170F to 215F. Response to a demand for heat is rapdi and uniform throughout the system. Steam...Continuous...Multiple Zone To provide continuous but modulated heat delivery in a multiple zone steam system, a two pipe vacuum is employed. Boilers are operated at pressures above atmosphere. Thermostatic control of system pressure is accomplished through opera tion of motorized valves on the steam main and high vacuum pumps on the return mains provide modulated and continuous heat delivery. A number of proprietary systems with the necessary steam specialties have been developed for this type of operation. Outdoor or indoor thermostats may be used. All radiation is installed with orifices. Page 7-3 10644 CAST IRON vs. STEEL BOILERS CHAPTER 8 CAST IRON vs STEEL BOILERS There are a number of differences between cast iron and steel boilers which every buyer and seller should understand. Steel boilers may be designed for greater pressures that are necessary for process steam used in manufacturing and power generation. Low pressure cast iron and steel boilers for heating are designed and constructed in accordance with the American Society of Mechanical Engineers Code for Low Pressure Heating Boilers. By this AEME Code, working pressures are limited to 15 psig for steam heating boilers and l60 psig for hot water heating boilers with a maximum temperature limit of 250 F. American-Standard cast iron steam boilers are therefore limited by the ASMS Code to 15 psig working pressure and 250 F temperature. All American-Standard cast iron water boilers were originally good for 30 psig working pressure. Recently the working pressure ha6 been raised to 50 psig and,on special order, boilers may be obtained for 80 psig. Refer to current catalog information for boilers available at these higher pressures. Regardless of pressure, hot water heating boilers are limited to 250 F. working temperature. Within those limits...and for all normal heating requirements...cast iron boilers have a definite edge over steel. As far as installation 16 concerned there is no clear-cut advantage of one over the other. Cast iron boilers delivered in sections require in stallation time to seal and bolt the sections together. Steel boilers are often delivered complete, ready to hook up. However, because of their size they need expensive rigging to handle and Jockey them into position. Steel boilers also suffer from the cost of replacement. In the case of ca6t-iron, replacement can often be made on a section-by-section basis...whereas with steel, damage to the 6hell often involves replacement of the entire boiler. And, when a steel boiler i6 installed in a new building with no pro vision for replacement, the operation requires the demolition and recon struction of a considerable wall area. The biggest advantage in cast iron is inherent in the metal itself. Cast iron is much less susceptible to corrosion than steel to begin with...and corro6ioty when it does start*haB a much more serious effect on steel. Page 8-1 10646 Rust will attack steel much quicker than cast iron and,when it does, it tends to bore through the metal, in a small area. This has the effect of making the metal thinner and therefore weaker. In the case of ca6t.-iron, it resists rusting longer and rust, when it does start,, spreads across the surface and does not eat into the iron. In addition .to giving much longer life, cast iron has one other big, inherent advantage over steel...it can be poured into molds, while 6teel must be formed and shaped in dies and presses, with various parts Joined by welding. Internal tubing on a steel.boiler, for instance, must be rolled into the plates (tube sheets) supporting them much like the copper gas line is flared at the connection to the carburetor In your car. This joint represents a weak point in the steel-boiler and^as weak points often do, is liable to let go Just when it i6 being pushed hard in severe weather when breakdown will cause the most inconvenience. Another advantage of molding cast-iron is that piping connections can be more flexible. In the case of steel, the practicalities of fabrication rather than desire govern the placement of connections. Cast-iron boilers are expandable within limits merely through adding sections. Many communities, for instance, are adding wings to existing schools. Where cast Iron boilers, .are used',, adding sections may take care of the new wing. If the expansion goes beyond the capabilities of a steel boiler, the entire boiler must be replaced, or a second boiler added...if there is room enough. Cast-iron boilers take up less space both in square feet of floor space and in total cubic feet, for the same capacity. This, too, is a result of pouring iron into the most ideal shape. Finally, because cast tiron uses a number of smaller combustion chambers, rather than one.huge.flame, controls can be simpler and less costly. And simplicity means lower maintenance cost and less down time. To Sum Up* 1 At pressures above 15 p. s. i. g. steam and 80 p. s. i. g. water...oniy steel can do the Job. Installation cost is a stand-off. Cast Iron Advantages 1. Less susceptible to corrosion. 2. Longer internal-connection life. 3* More flexible piping connections. 4. Readily expandable to handle larger loads. 5. Easier,. Ies6'expensive-replacement. 6. Smaller space requirements. 7* Simpler, less expensive controls. * ' (l1 Page 8-2 10647 STOKER-FIRED BOILERS 10648 CHAPTER 9 STOKER-FIRED BOILERS A mechanical stoker is a device to provide automatic fuel feed in a coal furnace, to provide a supply of air under automatic control for burning the fuel, and in some cases, to provide an automatic means of removing ash and other refuse of combustion. Mechanical stokers burn coal much more efficiently than hand-fired furnaces because the fuel feed is more uniform and more perfectly distri buted and because it provides more positive control of the oxygen necessary to combustion. Stokers may be roughly separated into four classes; Class 1; burning 10 to 100 pounds of coal an hour are used primarily for home heating. Class 2: burning 100 to 300 pounds of coal an hour are usually underfeed motor-driven 6crev-type stokers and are used extensively in apartment houses, schools, hotels and motels. Class 3: burning 300 to 1,200 pounds an hour and... Class 4; burning over 1,200 pounds an hour. With American-Standard cast-iron boilers it is unnecessary to go beyond the Cla66 2 stoker. Coal firing rates for American-Standard boilers are based upon coal having a calorific value of 13,000 btu per pound. Two measurements are sometimes confused; headroom and combustion space. Headroom 16 the distance between the top of the retort (the stoker basket that holds the burning fuel) and the boiler crovn6heet. The minimum headroom should be governed by this table for the Severn, Exbrook, No. 3 Redflash and A-7 boilers. Firing Rate pounds per hour Minimum Distance 0- 20 21- 30 31- 40 40-100 101-200 201-300 18 M 20 24 ft 28 tf 30 II 36 II This headroom is necessary when burning bituminous caal because of the tendency of coke "cones" to grow out of the fire bed, like stalagmites.in underground caves. If they build high enough to touch the crownsheet, they topple over, carrying with them the coke that has formed at the level of the 10649 This results in a thinning of the fire bed and the exposure of white hot coal6. This thinner portion of the bed offers less resistance to the air flow through the fuel bed, creating an intense blast condition. The intense local radiant heat generated is sufficient to cause breakage of the crownsheet directly over it. American-Standard boilers should not be stoker fired at fuel burning rates greater than those specified. To do so aggravates coke cone conditions and creates risk of boiler damage. Combustion space is the number of cubic feet required for complete combustion of the fuel. Combustion space must be large enough to avoid too high a btu release per cubic foot per hour. If too high a release for the combustion space is attempted we are faced with what is known as a bottled heating condition. This excessive heat for the space results in excessively hot front doors, warping boiler fronts, liquifying re fractory brick and damage to the walls of the stoker retort. The firing rates of stoker fired American-Standard boilers are satisfied by either Class 1 or Class 2 stokers. In mo6t instances, the stokers are of the underfeed type using a screw to convey the coal from a hopper or bin to the stoker retort. A hopper type Class 1 underfeed stoker, with a round retort. FIGURE 9-1 FIGURE 9-3 A Class 2 hopper type of under feed stoker with rectangular retort. Page 9-2 10650 * These stokers may burn either anthracite coal (pea, buckwheat, rice or barley size) or bituminous coal, usually pea size. When burning anthracite there i6 less tendency for the ash to clinker. As the coal burns the dry ash spills over the edge of the retort collecting in a well or on a hearth from which it may be removed manually or automatically. The burning of bituminous coal presents a different problem. The ash collects principally on the hearth around the retort. As the ash layer gets thicker the heat from the fire melts it and causes a clinker to form. This clinker i6 removed manually with clinker tongs designed for the pur pose. While a few Class 1 or Class 2 underfeed stokers are designed for automatic ash removal the major portion of them require manual removal of the clinkered ash. For best efficiency the quantity of air fed to the fuel by the fan must be kept in the proper proportion to the rate of coal feed. This may be done by setting a damper in the air duct but the wide variance in fuel bed conditions (thickness and porosity) make this type of control unsatis factory. Most modern stokers are provided with automatic regulation of the air. A draft regulator in the smoke pipe is used to control the over-fire draft within reasonable limits for best results. As with other fuel burning equipment, there must be an ample supply of air made available to the stoker if efficient combustion is to be ob tained. A stoker burning 100 pounds per hour of coal will require an air supply of 1,500 poun4s per hour or approximately 375 cubic feet per minute. Usually a direct opening between the boiler room and outdoors is needed. Page 9-3 k.r 10651 CHAPTER 10 OIL-FIRED BOILERS CHAPTER 10 OIL FIRED BOILERS Originally, crude oil was put through a straight run distillation process to separate it into various petroleum products; naptha, kerosene, fuel oil, gasoline and lubricating oils. The quantity of each from a barrel of crude oil depended entirely on the field producing the crude. Because of these fixed quantities a high demand for one of the products -- gasoline for in stance -- vould result in over production of the others. To overcome this problem the oil companies developed a thermal-cracking process by vhich the natural arrangement of the carbon atoms and hydrogen atoms in the oil is changed. This process made possible the production of varying quantities of products from the same crude oil. For example, larger percentages of gasoline could be produced In the summer. During the heating season the production of fuel oil vould be Increased and less gasoline produced. In the late 1930's the catalytic cracking process was developed. It has almost replaced the thermal cracking process since the same results are obtained, but at lower temperatures and pressures. The development of cat-cracking gave the heating industry some problems. While cat-cracked #2 heating oil can be produced chemically identical to dis tilled #2 heating oil, it ha6 different burning characteristics...it causes smoking, pulsing and noise in burners. This trouble, however, has been minimizied because burners are now de signed to handle both distilled and cat-cracked oils or blends. Oil is distributed in several grades. One of the lightest oils (No. 2) is almost always used in residential burners. Number 6 is the heaviest and is used primarily in the larger boilers. The heavier the oil, the higher the btu value. Common terminology refers to light, medium and heavy oils. Actually the numbers 1, 2, 4, 5 and 6 as grades .of heating oil and 10, 20, 30 as grades of oil in your car's crankcase indicate the relative viscosity. Viscosity is a measurement of the resistance to flow in a substance. The higher the viscosity, the higher the resistance to flow. The heavier the oil, the higher the visoosity. This table shows the approximate weight and heating values of standard grades of fuel oil. Commercial Standard No. 1 2 4 5 6 Weight lbB./gal. 6.951-6.675 7.296-6.870 8.212-7.206 8.488-7.778 8.571-7.882 Heat Value btu/gal. (000's) 137.0-132.0 141.8-135*8 153-3-140.6 155-7-148.1 157.3-149.4 Page 10-1 10653 The basic or standard viscosity of any oil is affected by temperature. A6 temperature falls, the oil becomes more viscous...develops more resistance to flow, becomes more sluggish. Obviously, above certain levels of viscosity, flow to the burner nozzle andy much more importantly, nozzle ability to atomize the oil would suffer. Because of their inherently low viscosity, temperature presents no prob lems in the case of the two lighter grades. In very severe weather, however, No. 4 oil must be heated to at least 0F to burn efficiently. No. 5 must be heated to at least 60F -- No. 6 oil to 120F. There are three basic types of burners; 1) High pressure atomizing 2) Low pressure atomizing 3) Rotary Cup The "High pressure atomizing" is the most common, least expensive end simplest in design. It uses the lightest of oils. It is supplied in capaci ties up to about 30 gallons per hour, and makes no provision for modulating oil flow. The oil is forced through the nozzle under heavy pressure (from 75 to 140 psig) so that it breaks up, or atomizes, as it leaves the nozzle. American-Standard burners are set at the factory for 100 psig. The "low pressure atomizing" burner (from 2-7 psig) is made in about the same oil-burning capacity as the pressure atomizing type, but because it can handle heavier oils (up toNo. 5) with greater btu values it can sup ply more heat at any given firing rate in gallons per hour. Here the oil and air are mixed before they reach the nozzle. Because the oil is emulsified before it reaches the nozzle, this type of burner re quires a larger nozzle which does not clog as readily. The "rotary cup" burner handles up to No. 6 fuel oil in capacities up to 150 gallons per hour...with the flow modulated as required by the load. A rotary cup, in the form ofa cone, replaces the nozzle. Spinning at 3600 RFM, the cup throws off a thin film of oil mixedwith small amounts of air, called primary air and equal to 10 or 15$ of the total necessary for complete combustion. The additional 85$ to 90$ of air, called secondary air, is brought through a secondary air door by either natural or forced draft. To review the four steps in oil-combustion, after the combustion chamber is warmed up; 1) The oil is atomized 2) It is vaporized or gas if ied by the radiant heat of the combustion chamber 3) It combines with oxygen in the air 4) It burns. Page 10-2 10654 The efficiency of burning is largely determined by the efficiency of vaporization. Thi6 factor makes it necessary to concentrate the radiant heat of the walls of the combustion chamber on the oil spray as it leaves the nozzle. For this reason, nozzles are designed to give a variety of spray patterns so that the spray can be tailor-made to fit the dimensions of the combustion chamber. Wide angle nozzles deliver a "sunflower" flame in short, wide combustion chambers and an infinite variety of narrow angle nozzles deliver longer, narrower "horsetail" flames depending on the ratio of length to width in longer, narrower combustion chambers. Oil spray should not be allowed to hit either walls or floor of the combustion chamber for two reasonsi 1. It builds up carbon on the wall 6 and floor of the chamber which shortens its life 2. It creates excessive smoke which deposits heavy soot layers on flue surfaces, lowering heat transfer efficiency and necessi tating frequent cleaning. The short, wide "sunflower" flame is quieter when small quantities of oil are used. In intermittently-fired boilers it is essential that combustion chamber walls heat up rapidly so as to reach maximum efficiency of vaporization as soon as possible in each firing cycle. Combustion chamber walls should be high enough to protect the lower portion of the boiler's water legs. Should an accumulation of 6ludge and scale exist in the water legs, restriction of normal water circulation may occur and dissipation of heat at that point restricted. Boiler damage could result. The following tables show typical combustion chamber 6izes for the various burning rates in gallons-per-hour of low and high pressure atomiz ing "gun-type" burners. Page 10-3 10655 Burning Rate GPH 4 5 6 7 8 10 12 14 16 18 20 22 34 26 28 30 COMBUSTION CHAMBERS DIMENSION TABLE; HIGH PRESSURE ATOMIZING BURNERS Length Inches 21 23 24 26 28 33 36 39 42 44 h6 48 50 52 54 56 Width Inches 17 18 20 22 23 24 26 28 30 32 34 34 36 36 38 40 Height Inches 17 18 18 19 19 19 20 21 22 23 24 26 28 30 32 34 Flame Center to Floor 8 8 9 10 11 12 13 14 15 16 17 17 18 18 19 19 Floor Area Sq.In. 288 396 480 572 644 792 936 1092 1260 1408 1564 1612 1800 1872 2052 2240 Burning Rate GFH Uo to 8 10 12 14 16 16-20 20-25 DIMENSION TABLE; LOW FRESSURE ATOMIZING BURNERS Flame Length Width Height Center Inches Rec. Min,. Inches Rec. Min. Inches Rec. Min. to Floor Rec. Min. Floor Area Sq. Inches Rec. Min. 34 32 38 36 45 40 48 44 54 48 56 50 60 54 21 19 22 21 24 22 26 24 28 26 32 30 34 30 18 16 19 17 20 18 22 20 22 20 24 21 30 26 10 9 715 640 11 10 840 755 12 10 1080 975 12 10 1250 1125 13 11 1525 1380 15 12 1780 1620 15 12 2040 1840 This table shows both recommended and minimum dimensions . If the minimum width is used, the recommended length should he used. In all cases length has more effect and, therefor^ more importance than width. Burning Rate GPH 9 16 25 35 50 60 76 100 125 DIMENSION TABLE; ROTARY CUP BURNERS Length .Inches Width Inches Height Inches Flame Center to Floor 39 20 30 49 24 30 57 27 32 77 39 37 90 45 38 105 54 38 112 60 38 118 65 45 130 70 46 10 10 12 15 18 22 26 29 32 Floor Area 790 H76k 1539 3003 4050 5670 6720 7370 9100 Page 10-4 10656 Large oil burning systems commonly use automatic draft regulators to produce a draft pressure over the fire of .02 to .025 inches of water. All oil burners should be installed in American-Standard boilers accord ing to the specifications of the burner manufacturer. Page 10-5 10657 CHAPTER 11 INDIRECT DOMESTIC HOT WATER HEATERS i i 10658 CHAPTER 11 INDIRECT DOMESTIC HOT WATER HEATERS The necessity for heating water, in either a hot-water or a steam heat ing system, naturally enough, gave somebody ideas of using the same boiler to provide domestic hot water. In the hot-water boiler the immersion control actuates the burner to maintain the desired boiler water temperature, summer and winter. Steam heating systems have a different problem. In the heating season, a thermostat or pressure-stat i6 the normal'burner control. But in the non heating season it is wasteful of fuel to maintain a steam pressure Just to heat domestic hot water. For the time when steam is not required, an im mersion control is installed below the water line of the steam boiler. By keeping boiler water at or near a specified temperature, domestic hot water Is provided even when the space thermostat is not operating. This means that one unit can provide both heat and hot water, eliminat ing the need of extra expense for separate water storage and water heating equipment..saving both space, and , during the heating season, fuel. Four types of domestic hot water heaters are used with boilers : 1. Internal Tankless (instantaneous coil type) 2. External Tankless (instantaneous coil type) 3. Internal Coil with storage tank 4. External Coil with storage tank The internal tankless heater uses a finned copper coil sub merged in the boiler water. To extract the most heat, the coil is fixed near the top of a hot water boiler and Ju6t below the surface in a 6team boiler, where boiler water temperature is high est. FIGURE 11-1 Page 11-1 10659 The fins are usually an integral part of the coil and never loosen. They are scientifically sized to minimize the amount of coil necessary to develop water heater capacity. The coil is designed to give maximum length without, however, restrict ing the flow of boiler water over and around the coil. Controls must maintain boiler water at the proper temperature during the non-heating season...usually between l80 F and 200 F. To insure quick response to a demand for hot water, the operating immersion control in the boiler water is usually located Just under the cold water inlet to the heater, so it will sense the temperature drop almost as soon as the domestic hot water draw occurs. Immediately the main burner Is switched on to keep the boiler water at the proper tempera ture . With American-Standard coil type heaters to provide maximum sen sitivity, the control is placed inside the loops of the coil where boiler water cools the quickest when a hot water demand draws cold water into the coil. During the heating season, controls in a hot water system lock out the circulator pump until any call for domestic hot water is satisfied. The call for hot water is usually completed in a few minutes and ha6 no notice able effect on heating the space. The external tankless heater carries its coil in a separate small "tank" of its own. Hot water from the main boiler is circulated through this coil tank, usually by gravity. The operating control is again placed adjacent to the coil inlet. FIGURE 11-2 Page 11-2 10660 In the case of steam, the coil and its tank are dropped down so that a horizontal upper pipe enters the "boiler Just below the surface of the boiler water. The internal tank type heater is a specially designed internal heater with a hot water storage tank added so that an initial supply of hot water is always available. Instead of a long lengths of small size copper tub ing, it uses a relatively short lengths of large size tubing to allow for flow by gravity. The hot water in the coil and tank is constantly circulated by gravity, out of the upper out let of the coil to the top of the storage tank, then out of the bottom of the tank, and back to the lower coil inlet. FIGURE 11-3 In some cases a mixing valve is installed Joining a cold water line to the output piping of the storage tank where the requirement is for water cooler than l80F. FIGURE 11-4 The coil of the external tank type heater is designed in the same manner a6 the Internal tank type. It is used when the boiler design does not provide for its installation in the boiler. Again hot water is circu lated through coil and storage tank by gravity and again, in the case of a steam boiler, the heater is lowered to allow for piping Just below the surface of the boiler water. Page 11-3 10661 Tankless Heater Performance - I-W-H Rated After extensive research and investigation on the rating of tankless heat ers, the Institute of Boiler and Radiator Manufacturers announced in 1956 the Indirect Water Heater (i-W-H) Code. This code stipulates that the tankless heater must be tested and rated in the boiler in which it is installed. The I-W-H Code takes into account all the variables affecting tankless heater performance; water temperature rise through the heating coil (40Fl40F); water flow through this heater coil (G.P.M.); boiler water temperature; water content of the boiler and boiler-burner input. By testing the tankless heaters installed in the particular boiler with which it is used, the code as sures accurate, dependable ratings. Not all tankless water heaters are rated according to the I-W-H Code. Some domestic water heaters of the tankless type are rated by the manufacturer of the water heater in terms of gallons per minute of water draw at 100F temperature rise (40F - l40F)...and on the basis of the heating surface of the coll that is in contact with the boiler water, plus the temperature of the boiler water. Usually, these ratings are obtained by laboratory tests conducted with the tankless heater installed in a large hot water tank where boiler water temperatures are simulated. Advantages of Indirect Water Heaters 1. Initial Investment costs are lower for the boiler with tankless heater. 2. Servicing and maintenance is reduced. 3- Life expectancy of summer-winter installations is greater for boilers which are not shut down in summer -- corrosion and pilot problems during sum mer months are minimized. 4. Space requirements are reduced to a minimum. 5 The copper tubing in tankless water heaters is highly resistant to corrosion. 6. In damp climates^ summer-winter installations help keep basements dry. 7- Domestic hot water i6 generated instantaneously. NOTE; Where excessive lime exists in the water, tankless type water heaters are not recommended unless provision is made for regular cleaning. Tank type heaters are recommended in hard water areas. Page 11-4 10662 HOW THE STEAM SYSTEM WORKS CHAPTER 12 HOW THE STEAM SYSTEM WORKS Basically, any heating system, like any electrical circuit, has three components: 1. The generator or boiler. 2. Circuitry or piping. 3. A load...the radiation. Providing each of the three components is in good working order and connected to each other with tight joints, a steam heating system needs only the removal of air and free return of condensate to function properly. System air is vented to the atmosphere and condensate is returned to the boiler to maintain the proper boiler water level, and to go through the next cycle of boiling to steam end condensing in the radiation as it heats the space. Air and condensate are removed from the system by a series of vents and traps covered in the next chapter (13). A steam boiler is not completely filled with water. When heat is ap plied to the water it boils and creates steam. A6 discussed earlier, it will boil at varying temperatures depending on the vapor pressure on the sur face of the water. At one pound gage pressure, one pound of water (l/62nd of a cubic foot) will create 25 cubic feet of steam. This represents an approximate 1,500 times increase in volume. This tremendous increase in volume builds up a pressure greater than the pressure in the piping and radiation. Since steam flows in the direction of a lower pressure it flows through the piping to the radiation. The piping normally, is insulated to prevent excessive condensation of the steam and lo6B of heat until the steam reaches the radiation. A steam system transfers heat from boiler to radiation in the form of latent enthalpy of vaporization. A hot water system transfers heat in the form of sensible enthalpy of the water. Page 12-1 10664 FIGURE 12-1 In Figure 12-1 the diagram 6hovs a simple one-pipe, up-feed system. The supply main is pitched downward to facilitate the gravity flow of condensate. Some definitions; The supply main carries steam to all radiators. After the last piece of radiation the piping back to the boiler is called the return. At the end of the pitched supply main a drop-l'eg carries con densate back to the boiler room level. Piping from drop-leg to boiler is called a wet return because it is below the boiler water level and com pletely filled with water. Actually the water level in the drop-leg is always a little higher than in the boiler, during firing cycles. Resistance to flow in the supply main acts to decrease the pressure on the water surface in the drop-leg which causes the water level to rise. And still more height of water in the dropleg i6 necessary to overcome the resistance in the return. For gravity return of condensate, the minimum clearance between the boiler and the water level and the end of the supply main is 18" t ' X* V * ft ' Page 12-2 10665 FIGURE 12-2 Frequently in one-pipe systems it may not be practical to run a vet return from the end of the staam main back to the boiler. In such instances a dry return is installed near the ceiling. As shown in Figure 12-2 with the drop-leg located near the boiler. The radiator runout creates a possible noise problem if not properly installed since the condensate must flow back through the runout against the flow of the steam. The noise problem is most acute during the heating-up period. Cold radiators condense the steam very rapidly. This means greater steam velocities flowing against greater quantities of condensate. RADIATOR FIGURE 12-3 Page 12-3 10666 A quieter system, though more expensive, is the two-pipe up-feed layout. Figure 12-3. Here the condensate from the radiation is carried out the other end of the radiator and flows through a separate condensate return back to the boiler. Condensate and 6team, then, flow in the same direction, eliminating water ham mer . Note that the return pipe is above boiler water level and is not com pletely filled with water. It is, therefore, called a dry return. The two pipe system uses a trap at the outlet end of each radiator to allow air and condensate to escape but holds steam in the radiator, (see Chapter 13). FIGURE 12--hDownfeed -- Figure 12-k -- where the steam main is above the radiation, are used on larger installations, primarily to eliminate counterflow of 6team and condensate in one-pipe systems and because of building geography in twopipe systems. The dripping of downfeed ri6er6 also provides drier steam which puts a smaller load on condensate traps in the radiation. Page 12-4 10667 However, the upfeed system, if dripped properly, can do as good a job as the more costly dovnfeed system. All four of these piping arrangements are possible in a gravity system ...where the condensate is returned to the boiler by gravity alone. FIGURE 12-5 It is sometimes necessary, as shown in Figure 12-5, to install a condensate pump to pump condensate back to the boiler; 1) When radiation is below the water level on the boiler. 2) When the system develops great quantities of condensate... e.g. a system using unit heaters (see Chapter 29) where fans blowing cold air over the steam coil condense it very rapidly, particularly at the beginning of the daily heating cycle. 3) When the geography of the building defeats easy gravity flow. (a) Radiation considerably removed from the boiler when it is uneconomical to enlarge pipe size sufficiently, and there is not room enough to pitch the pipe severely. (b) When the condensate return must be high to avoid door ways, windows, etc., and also to keep floor-space free. 4) Or any combination of these. Page 12-5 10668 SUPPLY VALV1e-4~[ lUCZZlffCZV raoiator trap CITY WATER TI'~*--------- ^l ------- --t\- \ V h ______JL---------J ('f*' - HARTFONT LOOP I | 1 UNION-. r2` I cz: % RECEIVER TANK VENT cT WATER |.IN_ tt1f" -- " FftT TRAP *WATER CONTROL f--------------- ' RECEIVER_L_ POMP MOTOR l-EL moTO PUMP-' AUTOMATIC WATER FEEOER^ CCOONNODRENNSATION PUMP FIGURE 12-6 In large steam systems it is usually necessary to have a receiver tank to hold extra water for the system. This tank receives the condensate from the condensation or vacuum pumps in the system. See Figure 12-6. The boiler feed pump draws water from the receiver and delivers it to the boiler through a feed water regulator. When the condensate in the receiver is insufficient to satisfy the boiler demand, a float operated valve automatically adds make-up water to the tank. A receiver must be used when the boiler has insufficient water holding capacity to fill the piping and the radiation with steam. To repeat; Only two things are essential to the proper functioning of a steam system; 1. Removal of air 2. Removal of condensate This chapter has discussed four different piping arrangements for steam heating systems. The next three chapters, covering accessories piping, will occasionally refer to system pressure. The four different kinds of pressure systems, above atmospheric pres sure, subatmospheric, vapor end vacuum systems will be covered in detail in Chapters l6 and 17. Page 12-6 10669 STEAM ACCESSORIES 10670 CHAPTER 13 CHAPTER 13 STEAM ACCESSORIES A full range of steam accessories is necessary in all but the small est of domestic systems. Accessories accomplish just two things; 1. Removal of air. 2. Easy return of condensate. By accomplishing these two things, they assure proper transmission of steam through the system. Radiation Air Vent This is a typical air vent in one pipe low pressure systems. It is located as low as practicable on the opposite end of the radiator from the supply. _ The float body, with a flexible diaphragm base, has a volatile liqnid charge which vaporizes easily under the steam temperature. FIGURE 13-1 At the beginning of any heating cycle, as steam enters the radiator, it pushes the air ahead of it. The air is vented through the port. When the steam has filled the entire radiator, having pushed all the air through the vent, it also fills the shell of the air vent. The liquid in the float body vaporizes, the diaphragm base expands, pushes against the base, raises the float body and the float needle which seats in the top of the chamber preventing the steam from escaping. With the burner off, the steam condenses, the vapor within the float body cools and condenses, the diaphragm collapses and the float needle is withdrawn from its seat, allowing air to re-enter the radiation. The air vent shown has an adjustable port to regulate the venting rate ...an Important feature when several radiators in the same enclosed space do not heat up uniformly. By adjusting the venting rate they can all be brought to full steam capacity by approximately the same time, providing a better balanced system. Page 13-1 10671 FIGURE 13-2 FIGURE 13-3 Vacuum Vent The Vacuum vent Is very similar to the air vent (13-1). The baiic difference is the vacuum check valve Just above the port. When the float needle is with drawn from its seat as the steam condenses, this check valve closes, preventing re-entry of air into the system. These valves are used on one pipe vapor systems...one on each radiator. Main Air Vent This larger capacity air vent is used at the end of steam mains and dry returns -- about 12 inches back from the drop leg. Its operation is identical to that of the radiator valve described in Figure 13-1. It is used on pres sure systems. Page 13-2 V i r 10672 Bait 'Float support Atmospheric tube -- Syphon Main vent (vacuum) FIGURE 13-4 THERMOSTATIC | OUTLET Disc Type FIGURE 13-5 Bellows Type FIGURE .13-6 The vacuum vent valve illustrated in Figure 13-4 is applicable to mains and dry returns in vapor steam systems. It vents quantities of air easily and quickly. The check valve pre vents air from re-entering the piping when the system cools down. Thermal. Trap The most efficient air vent lo cation in steam radiation is at the bottom of the radiator. Unfortunately, in one-pipe systems it is impractical to put air vents so close to the floor, since they may be damaged. Two-pipe steam systems are more advantageous. The thermal trap which is located at the radiator discharge passes both air and condensate. Thermal traps are used on all two pipe systems; pressure vapor and vacuum. There are two common types; disc and bellows. In each the thermostatic clement is charged with a volatile liquid. Air and condensate enter the thermo static trap at the connection marked "in let". If the condensate is cold, the thermostatic element remains contracted and the air and condensate pass through the orifice to the return main. As the condensate gets hot the pressure generated by the volatile liquid expands the bellows and closes the port. The trap will not re-open until the condensate cools. At this time the cycle of performance is repeated. Exactly the same result is achieved with the bellows type trap - Figure 13-6 l 1 Page 13-3 10673 valve: access PLUG VALVE AIR VENT OUTLET INLET DRAIN PLUG Single Port FIGURE 13-7 o Float Trap As condensate builds up in the trap, the float rises, opening the outlet valve. x VALVE ACCESS PLUG MULTIPORT VALVES OUTLET DRAIN PLUG Multiport FIGURE 13-8 AIR VENT The steam in the chamber forces condensate out of the trap allowing the float to fall and close the valve, before any steam can escape. FLOAT The multiport float trap is indicated where the amount of con densate to be handled varies. The float, depending on its height, will open one or more pcrt6. These float traps are used for dripping heels of up-feed systems varying in pressure from vacuum to 200 psig. In the case of low pressure systems (vacuum - 15 psig.) , the trap should be equipped with a thermostatic air vent. Float traps are better suited to systems where condensate removal is continuous. They should be well-made. False economy in float trap pur chases will result in steam leakage and sticking of moving parts. .y Page 13-^ 1 (, ' 10674 thermostatic 01 SC ELEMENT FLOAT L valve and oftrFiCE Combination Float and Thermostatic Trap This trap is merely a combination of float and thermal traps. Air is vented to atmosphere ahead of the steam and condensate because the thermostatic disc element, in its relaxed position, holds the port open. FIGURE 13-9 When steam or hot condensate gets to the trap, the disc expands and closes the port. As the condensate level rises, the float opens the outlet valve and steam pressure forces the concfbnsate into the return main. Float and thermostatic traps are used for dripping mains and supply risers in systems varying from vacuum to 40 psig vhere large quantities of condensate must be returned. FIGURE 13-10 Upright Bucket Trap This diagram shows a typical upright bucket trap. Condensate enters the inlet. As it rises the bucket floats and closes the outlet valve. Eventually, the outer lip of the bucket runs into the baffle of the body of the trap and i6 held stationary. The condensate continues to rise, flows over the sides of the bucket and 6inks it, opening the outlet valve. Condensate 1b discharged from inside the bucket until the bucket regains its buoyancy and closes valve. Page 13-5 10675 OUTLET INLET Inverted Bucket Trap The inverted bucket trap il lustrated in Figure 13-11 is dis charging. Pressure at the conden sate inlet is forcing the water out of the bucket and into the trap body. As the water leaves the bucket it is replaced by air and steam, the bucket becomes buoyant, rises and closes the orifice. The escape of air from inside the bucket through small bleed hole, marked air vent, permits more con densate to enter. Shortly, the bucket loses buoyancy, sinks and the dis charge portion of the cycle is repeated. FIGURE 13-11 Air is automatically eliminated through the small air vent at the top of the inverted bucket. They are particularly suited to systems handling abnormal amounts of both air and condensate. They come in sizes from 5-" to 3" and. for pressures varying from vacuum to 2,400 psig. They are particularly suited to high pressure systems. Both types of bucket traps are used for draining air and condensate from blast coil6, unit heaters and steam mains. They both use large size exhaust ports. They are designed for use in systems where high pressure might collapse a float. Combination Bucket-Thermal Traps With blast coils and unit heaters in low pressure systems, bucket traps are equipped with bellows or disc type thermal traps for venting air. The bucket element returns the condensate. Page 13-6 10676 VENT TO ATMOSPHERE FIGURE 13-12 FIGURE 13-13 Boiler Return Trap When the pressure difference between the boiler and the end of the dry return is too great to permit proper drainage of condensate back to the boiler, a boiler return trap is used as shown in Figure 13-12. The trap should be located close to the boiler and about 18 inches above the boiler water line. During the period the trap is collecting condensate, the float has dropped. See Figure 13-13. Conden sate flows from the end of the dry return, down the drop leg through through check valve A and up into the trap. Check valve B prevents water from leaving the boiler. Also during this process air in the trap may be vented to atmosphere or back to the dry return where it is discharged to atmosphere through a vent valve. Eventually the float rises, closes the air vent port and open6 the steam inlet port, allowing boiler pressure to enter the trap through the balance pipe from the steam main. Both trap water and boiler water are now under the same steam pressure. The additional head, because trap water level is above boiler water level, closes a check valve A to condensate return and opens a check valve B to the boiler return and condensate flows from trap to boiler. Page 13-7 10677 Impulse Traps In steam mains, unit heaters, laundry equipment, sterilizers, and other equipment impulse traps are used for draining widely varying amounts of condensate. Pressure at the trap outlet must he 25# or less than the pressure at the trap inlet. Condensate Pump In some steam systems the end of the main is too low to permit the condensate return to the boiler by gravity. A condensate pump must be used. A condensate pump consists of a motor-driven centrifugal pump plu6 a receiving tank with an automatic float level control. Condensate flows by gravity into the return tank, the top of which must, of course, be below the lowest return. A vent, run to at least 10 inches above the boiler water level, avoids pressure in the tank, allowing it to fill properly. The float level control in the tank, when it reaches a specified height, actuates the pump motor. The water in the tank is then pumped into the boiler through a swing check valve located as close to the pump on the boiler side. Make-up water, regulated by another float valve in the receiving tank Is delivered to the tank. Vacuum Pump The vacuum pump draws air and condensate from the return side of the system...separates them...and discharges air to the atmosphere and pumps the condensate back into the boiler. Low vacuum pumps can maintain approximately 10" of vacuum...high vacuum pumps, 20" or more. Where a return from the system is below the inlet to the receiver, it is necessary to install an accumulator tank below the lowest return along; with a pump. The accumulator pump is also controlled by a float lever. Page 13-8 -\067S Vacuum Lift The vacuum lift demonstrateb one of the advantages of a vacuum steam system. It can raise condensate from a radiator or return to a higher level in the return system. Nvturco Lirr riTTlHG 04 CL* OW* 4 3B LlfT P\Pt OIA. Of VACUUM HCTU4N A Assume a return main (A) below return main (B). Condensate will accumulate at bend (C) until it fills up the bend sealing off A from B. Because the vacuum pump reduces the pressure on the outlet side B, the slug of water in the elbow will be drawn up the vertical pipe into return main B. FIGURE 13-14 I TOTAL litt l not OVE * rT. IT MOftt than TT U1C UO*t THAN 1 ITITl VACUUM ACTUftN nn WCMC* 'A Vi A* IK ; 4 a 10 14 a 1a 4 ta a 21 24 UAXIUUU LENGTH A (ACOVM AtTUM Single lifts should be limited to 5 feet. When lifts are greater than 5 feet, a step lift is employed. See Figure 13-15 Lifts should be avoided whenever possible. FIGURE 13-15- Page 13-9 10679 Generally, steam mains are not sized smaller than two inches -- fewer hangers required to prevent sagging. On large systems the end of the main is kept at least half the size of the main at the boiler. Mains should be pitched at least l/4" every 10 feet, and radiation connections should be pitched 1/2" per foot. Where radiator runouts longer than 8 feet cannot be pitched 1/2" per foot, use the next largest pipe size. Tables 15-4 and 15-4A show nominal pipe sizes for returns -- both mains and risers -- for varying pressure drops from l/32 psi to l/2 psi. Again the pressure drop is assumed to occur in 100 feet, from an initial pressure of 3-1/2 psi, and the figures in the body of the table represent capacities in EDR. Three columns for each pressure drop are shown-wwet, dry and vacuum returns. This table can be used in sizing the piping on two-pipe systems. The wet return eolumn is also used for one-pipe systems. '! . L < i Page 15-5 10680 R e tu rn M ain and R is e r C a p a c itie s f o r Low -P ressure Systems---- EUR Sheet 1 o f 2 888 8888i H t-W 00 O c-- r-- o CM H-3VOOVOCMCOCM H H CM COM3 >i ug o H e M3 ONOQi CM f-VO O < covo o roe H CM nc-o UV 8888888 c-- cm ao o c-- r- o H -3 V0 O VO CM <--i I--( CM COCMVO W.OPPggO os O >< VO t-- C-- CM VO -3 CM _ CM O H uo OO MO CM -3 C-O O IA4 H COMOCO CHOCHO HmiOA ro cj" ug o H ffi -3 Vp -3 O CM O CO 00-3 -3- C--m3 1 CM WO CT\ H -3 CM < CM nOVO CO co CM SCW CM O O O O O <3\ f--J- CM CM O CM i uoVOn --mo^CM to uo CM ^ co I H covo cO coco HH 88 r-- cm OOI CrM- Ct--M <i o< Ct--M I( HH-3VOOVOCWCOCW H H CM COM3 CM CM CM O ' OMAffvO I H -3 Ov wo i H co illl CM VO CM O O O i o o o t- f-- LTV VO -3 CM i MO OO LT\ CM -3 C- ( CCM MCMAOJ H CO MO CO CO t~- H O H H CO MO CM CM CM Q < Oo uo OO O < H -3 Oo M0 < H co o 2 ON CM H U o H 8 CcMo ii IIII CQ 3 CC0-MM 3CcMy C^O -og _o3 < l CM MO CO o CM r- i H CO WO f- H 8 cm cm o o o o o uo MOO CM CM O CM I MO CO COCO t--UOO I/O ** ** * H CM m3 C-- H UO 8CM CM CM HOn 3UO CuOM<A h co iiii BiP> H jVOd T* *H d CO -3 -3 CM CM CM CO HIIH HI HI CO -3 -3 CM CM CM M CO HI M* CO H HHHCW CM CO CO -3 MO VO 06 HHHCWCUCOCO-3 MO Page 13-6 10681 T a b le 15-bA Sheet 2 o f 2 W'OWOOOOQOOO fO C-- Ovvo W W J O Q O O O< rlO\fO(nrOO\OJNOWW > p H miAPrACOh Orn-dIA* W\oOC\ihA N O 00 Vo H 2 C\J ~v H w I I I Cfl 6 -P Q >> to o u ta <a 4) & O < > iiii iiiii i i i i i i i i i :88 -4 -4 88 13- 3 5 vo O H OJ tnto onH W3 t^4-' H OJ 103 t-- OJ 8O 3 oo i V4Q Vepiirr-i\ro-33 6O nOJuOvJ i H roirv0 3 ,--l HHW Soi Vi ta t> 0 1 O P o CO M O OJ V o M d2 CO + 88 :88 t -3 -3 < ` -3 -3 <--I CM (OCO CO H OJ 3 H OJ <03 covnj-\r)QOOOO vo CKO COCO OJ O OJ -3 o LT\ C\ t~-VO VO vrv OJ f-OJ < r-l OJ 3\ OV SO, OJ r-i ^t CO H OJ tO IOCO S! I -it < oo oo &&I H 04 4- OnoTon iH H 8888 I O tC-- 0o--VvOo 33-000 I Hi-IOJtcvOvirvOjH VOWOOOOQ f- C\VO OJ OJ -3 O Ov <o to to Cr> oj OJ 88 OJ OJ H cniAHCO O t/> cv/ Q\ t H H fO-4 VO O { HH llliItli|i III till 88 -4 -it ( 188 > -4 -4 > VO H OJ rOCO m H CM -it f-^t H OJ rO-4 r-oj OJ OJ QJ Q CH\ -iftN OOvMOAi hm IIl iiiiiii ^Ot-v'CCoKvSo OsoJ5Ooj0OcJ0- 3oQi <Q35QQh * H OJ Vf\ OMHfV OOJJ Hm 3 ltv CcoO WCT\ OioJ\ OgJv oQ H3 OUiAftO i l H* ro* II ta V 4) J3 P N O TO 3^ 3^0J^ OJ OJ CO HIHI *HI* 4I H H i- OJ OJ CO (03 ITvVO 3 3 OJ OJ OJ (O H H rl r( rl 01 Rl (*1(03 (A .Page 15-7 C 10682 v -C ^J lO O j [lOoU. , .JlO O P<_5^ 15-6 10683 FIGURE 15-1 The schematic drawing (Figure 15-l) shows a typical one-pipe low pres sure system. Since it is most frequently used, we assume a designed pres sure drop of l/8 psi. All pipe sizes are shown. However, using our tables, let's see how they were calculated. Pipe sizing is always started at the top of the steam riser farthest from the boiler -- 1 to 5 in this example. Since this is a one-pipe system in which the condensate flows against the steam we use Table 15-3 to 6ize all steam risers and radiator runouts. All runouts are 5 feet in length and can be installed with the proper pitch of l/2" per foot. Since the smallest radiator on this riser has an EDR capacity of 30 square feet (which is larger than 28--See Table 15-3), the radiator runouts must be at least 1-1/4" pipe, which will accommodate all pieces of radiation up to 64 EE. The radiator larger than this, upper left, with an EDR of 100 square feet, needs a 2-1/2" pipe. To size riser #1$ which must supply two radiators with a total of l6o square feet of EDR, we find under the heading "Supply Risers Upfeed" that a 1-1/2" pipe will not do it, but that a 2" pipe will handle up zo 288 square feet of radiation which will not only take care of the 160 in the two top radiators, but will also serve the additional JO square feet in the two radiators on the next floor down. So, we can use two-inch pipe in both Risers #1 and #2. However, the addition of 80 more square feet of EDR on the next lower floor raises the accumulated total to 310- This, the table tells us, needs a 2-l/2" pipe for Riser #3> Adding 80 more square feet of EDR for the first floor radiation...a total, now, of 390, is still well below the maximum of 464 for 2-1/2" pipe so that we can use 2-1/2" pipe for Riser #4, too. All other risers and radiator runouts can be calculated from the table in the same way, except the 50 square feet of EDR radiator to the right of Riser 8 on the second floor. The amount of radiation calls for a 1-1/4" pipe, but because the runout is 10 feet long and we can't get l/2" pitch per foot, we use the next largest pipe size, 1-1/2". The next step is to size the riser runouts from steam main to risers; 5 to 21...10 to 22...15 to 23...20 to 24. Since these runouts are dripped and do not carry condensate flowing against the steam, they are sized ac cording to Table 15-2, under the column l/8 psi. Adding up the total load on each riser we get for riser runouts... Square feet of EDR 5 to 21 10 to 22 390 620 15 to 23 610 20 to 24 520 J fc 10684 To complete the supply side of the system we calculate 6ize6 for the four steam main segments. Again, "because the risers are dripped we use the l/8 psi column in Table 15-2. The load is increased by the load of each riser as the boiler connection is approached. Cumulative Steam Main Riser Load Pipe Size 21 to 22 22 to 23 23 to 24 24 to boiler 390 1,010 1,620 2,140 sq.ft. " "" "" 2" 2-1/2" 3" 3-1/2" To figure pipe sizes in the returns use Table 15-4A and the 6ame pres sure drop: l/8 psi. The "dry" return 21 to 25 has a load of 390 Square feet, so & 1" pipe will handle it. The riser drips (5 "to 27- .10 to 28...15 to 29-. .and 20 to 30) are a31 "wet" and carry loads of less than 1,000 square feet which is indicated in the "wet" column as needing a 1-1/4" pipe...all riser drip6 in our example can safely use a one-inch pipe.4 We complete sizing the system by sizing the wet return by segments; 25 to 26...26 to 27...27 to 28...28 to 29...29 to 30...30 to 31...31 to boiler connection. As in sizing the steam main segments we increase pipe size as load in crease closer to the boiler connection. Again using the "wet" column we get; Return Segment Cumulative Load Sq. Ft. Pipe Size 25 to 26 26 to 27 27 to 28 28 to 29 29 to 30 30 to 31 31 to boiler 390 390 390 1,010 1,620 2,l4o 2,l40 1" 1" 1" 1-1/4 1-1/4 1-1/2 1-1/2 The following table shows a step-by-step procedure for sizing the pip ing in this example. It is also a form to follow in estimating Jobs. Take the time to study it carefully...then set up a duplicate on a blank paper -- leaving; out only the last column. Then using the tables, calculate all the pipe sizes required. Like most old proverbs, it is true that practice makes perfect. L fi' Page 15-10 10685 Table 15-5 Procedure Step Part of System Section of Piping 1 Radiator runout 1 Radiator runout II it ir ii n n 1 2 2 3 3 U u 2 Riser 1 to 2 3 tt 2 to 3 U It 3 to U 5 M U to 5 6 Radiator runout 6 11 6 tr 7 TT 7 n8 it 8 ti 9 n9 7 Riser 6 to 7 u 7 to 8 11 8 to 9 n 9 to 10 E.D.R. Sq. Ft. 60 IDO 30 Uo 30 3o Uo Uo 150 230 310 390 100 100 100 100 50 5o 60 60 200 Uoo 5oo 620 Theoretical Pipe Size 1-1/U 2-1/2 1-1/U 1-1/U 1-1/U l-VU l-l/u i-VU 2 2 2-1/2 2-1/2 2-1/2 2-V2 2-1/2 2-1/2 L-VU 1-1/2 l-VU l-l/u 2 2-1/2 3 3 Page 15-11 - < r, ' 10686 Table 15-5A Procedure Part of Section of EDR. Theoretical Step____________ System ______ Piping__________________ Sq Ft,_________ Pipe Size Radiator runout rt u ti it tl 11 tl Riser 1! tt U Radiator runout it tr n ti n tt tt Riser ti n Tt Riser runout ii n u 12 12 13 13 Hi lii 11 to 12 12 to 13 13 to ll; li; to 15 16 16 17 17 18 18 19 19 16 to 17 17 to 18 18 to 19 19 to 20 5 to 21 10 to 22 100 2-1/2 100 2-1/2 100 2-1/2 100 2-1/2 50 l-l/li ho i~iA 60 l-i/U 60 1-1/4 200 2 i|00 2-1/2 1|90 3 610 3 100 2-1/2 100 2-1/2 50 W/l* 50 wA 5o 1-1/I1 5o i~VU 60 i~iA 60 1-1/U 200 2 300 2-1/2 Uoo 2-1/2 520 3 390 2 620 2 Page 15-12 10687 Table 15-5B Procedure Step Part of System Section of Piping 10 (cont'd.) 11 12 13 1U Riser runout tl 15 to 23 20 to 2k Steam main tl tt tt 21 to 22 22to 23 23 to 2k 2k to boiler Dry return main 21 to 25 Riser drip 11 tl tl 5 to 27 10 to 28 15 to 29 20 to 30 Wet return main tl tl tt tt tt tt 25 to 26 26 to 27 27 to 28 28 to 29 29 to 30 30 to 31 31 to boiler O CM EDR* Sq*Ft 610 520 390 1010 1620 21i|0 390 390 620 610 390 390 390 1010 1620 2U4.O 21ii0 Theoretical Pipe Size 2 2 2 2-1/2 3 3-1/2 1 1 1 1 1 1 1 1 i-i/U W/li 1-1/2 1-1/2 Page 15-13 10688 For two pipe systems (low pressure, vapor and. vacuum) pipes are sized in the same way. A pressure drop of l/8 psi is recommended and the same pressure drop should be used for steam mains, risers and condensate return piping. Tables 15-2, 15-3 and 15_i+ should be used. And again, mains should be pitched l/4" in 10 feet, horizontal runouts to risers and radiators should be pitched l/2" per foot and the next larger pipe size should be specified for runouts of over 8 feet where a l/2" pitch per foot is not possible. Page 15 -1*+ 10689 CHAPTER 16 I PRESSURE STEAM SYSTEMS t- 10690 CHAPTER 16 PRESSURE STEAM SYSTEMS Steam heating 6y6tems operating under pressures higher than atmosphere (gage pressures) are classified a6 either low pressure (up to 15 psig) or high pressure (above 15 psig...usually 30 to 150 psig). Thi6 chapter will be mainly devoted to the low pressure system begin ning with the review of some of the basic material covered in Chapter 12. A one-pipe low pressure system uses the 6ame pipe to carry 6team to the radiation and condensate back to the 6team main. SUPPLY VALVE AIR VENT 18`MIN. LCAP FIGURE 16-1 This is a typical one-pipe up-feed system with gravity return usually found in residences. This arrangement has limits on its size and capacity. As the steam is generated in the boiler, it pushes the air in the sys tem ahead of it and out the vents on each radiator and the main vent at the end of the supply main. When steam hits any vent, it closes. The supply main is pitched away from the boiler to carry condensate in the same direction as the 6team is flowing. Page 16-1 'I. * , 10691 dI-_-_--_-_--_-^T*veIHnt STEAM MAIN -ORIPLEGS WATER LINE WET RETURN FIGURE 16-2 This version of a one-pipe up-feed, system shows the risers being dripped into the wet return. FIGURE 16-3 Another piping arrangement is the overhead main or dovnfeed system. It is often used in multi-story apartment houses. (See Figure 16-3). The dovnfeed risers are dripped into the vet return. This arrange ment, of course, also allovs for carrying the design load quietly. Page 16-2 i } 1 c1 10692 FIGURE 16-4 This variation...with & dry return...is used where a wet return is either impossible or impractical...in most cases where there is only a partial basement. Note that we need the same 18" clearance between the end of the dry return and the water line as at the end of supply mains in earlier examples. FIGURE 16-5 Occasionally a limited ceiling height in the basement will not allow for this minimum 18" clearance between boiler water line and the end on the steam main. The solution is to dig a pit and set the boiler enough below the floor level to provide the clearance. Page 16-3 * r, 10693 In all one-pipe systems the steam main i6 vented as well as each piece of radiation to allow for quick elimination of air. One-pipe systems should use vent valves with adjustable venting rates. This kind of valve provides uniform distribution of steam throughout the system, particularly on automatically fired Jobs. By adjusting the venting rates at each radiator, a more uniform heating of each room is obtained. Of course, the boiler must produce enough steam to fill all pieces of radiation. Another type of vent valve used on radiators is the vacuum vent which allows air to escape but prevents its re-entry into the radiator. These valves are sometimes used on radiators in one-pipe steam systems to convert the system to vapor type operation. These systems so con verted should not be confused with the conventional two-pipe vapor system which is discussed in the next chapter. FIGURE 16-6 To fully explain the necessity for an 18" differential between boiler water level and the end of the steam main or dry return... Our steam system is, in effect, a giant, closed "U" tube with a boiler built into it. The water in the tube seeks its own level, and with the boiler shut down, will stand as high in the drop leg as in the boiler. With the boiler firing, pressure will build up from the surface of the boiler water and flow in all directions, pressing down on the surface of the water in the boiler and also on the surface of the water in the drop leg. If both pressures were equal, the water in the leg would continue to stand at the same level as the water in the boiler. Page 16-k J 10694 However, Borne pressure is lost in overcoming the friction in the steam main. Assuming 16 ounces of pressure at the "boiler end and 2 ounces of re sistance to flow in the steam main, then pressure on the water in the leg would be only 14 ounces...a pressure drop of 2 ounces or l/8 psig. Since one pound of pressure is equal to 28" of water (see Chapter 2), a drop of l/8 p6ig means a rise in the water level in the leg of 3-1/2". Resistance to water flow in the wet return is estimated at 3-1/2 and must also be added. The normal total rise of water in the drop leg becomes 7 inches. Allowing 11 inches of additional height for the greater pressure drop occurring during heating up of the system and as protection against surging makes the total height between normal boiler level and end of the steam main l8 inches. FIGURE 16-7 When the available head room will not allow the recommended 18" clear ance, the boiler can be pitted as shown in Figure 16-5, or a false water line can be established by the use of a condensate pump and float and ther mostatic (F & T) trap. (See Chapter 13). The water line of the condensate pump is the new theoretical water line of the boiler, eliminating the need for the mlrHmum 18" clearance between water line and the end of the main. The use of condensate pumps allows for a number of variations in onepipe systems. Page 16-5 i V i 1 10695 FIGURE 16-8 Another problem sometimes encountered with one-pipe systems is the necessity for an exceptionally long main in a lov-ceilinged basement. The answer is to drip the main when it reaches 18" above the water line and then use a riser so you can continue the proper pitch from a higher level. Thi6 method of handling head room problems must 6till consider pres sure drops to the end of the last main section and pipes must be sized accordingly. This is just one example of the fact that, when the basic fundamentals of steam flow and pressure drops are observed, steam piping can, literally, be bent like a pretzel. RADIATOR VALVESSTEAM MAIN d ij-dAIR VALVES-\ j 1 1 >_________ ir -J i 1--r 1. ----** J -ORAINS FIGURE 16-9 The original two-pipe, low pressure system had a number of built-in weaknesses. Page l6-6 f 1 10696 Here each piece of radiation drips into a dry return (the second pipe). The most obvious fault was steam entering the return leg of a radiator and closing the air valve before the radiator was fully vented, resulting in a partially filled radiator. Another problem was caused by closing the supply valve to any radiator. With the return valve open, the system itself was open to the atmosphere, creating an unbalanced pressure that could back water out of the boiler. RAOIATOR FIGURE 16-10 With the advent of the radiator steam trap, the two-pipe system took a little different design. The angle valve on the return end of the radiator is replaced by a radiator steam trap. The trap passes both air and condensate into the return. All air is vented from the system at the one main vent. Because the traps stops its flow, steam cannot pass through a radiator into the return and feed back up the return side of another radiator, closing the air valve and sealing air into it. However, this system still has the fault of being open to the atmos phere through the single air vent. With the traps closed, the pressure on the water in the boiler can become considerably higher than the pressure in the dry return, causing the water to back out of the boiler and into the dry return, sealing off the air vent and air-binding the system. 'i f 1 ` Page 16-7 10697 The drawing calls for a differential of 30 inches between boiler water level and vent. This means that if we confine the system total pressure drop to 8 ounces (l4 inches of water) or less, the vent will continue above vater and air released properly. In systems where air binding becomes a problem, a boiler return trap can be installed. Some years back American-Standard sponsored an "adjustable orifice system" which was of this same general design. Orifices in the supply valves could be adjusted to the size of the radiator. Theoretically, no traps were necessary to stop steam flow into the return, because 6team was supplied to the radiator in direct relationship to its ability to con dense it. It is still necessary to maintain 30" between the end of the dry return and the water line. A number of these systems are still in use. These are the principal variations in low-pressure steam systems. There are, too, high pressure systems for very large buildings and for process work where cast iron boilers have little or no application. Page 16-8 10698 CHAPTER 17 STEAM SYSTEMS PRESSURE BELOW ATMOSPHERE CHAPTER IT STEAM SYSTEMS -- PRESSURE BELOW ATMOSPHERE There are three different kinds of two-pipe steam heating systems that operate at. pressures below atmospheric pressure or under vacuum. 1. The vapor system 2. The vacuum system 3- The subatmospheric system The Vapor System Vapor systems are intermittently fired usually under the control of a thermostat. When starting the system, the burner operates until above-atmospheric pressures are generated and the air has been expelled from the system. During the off-period of the burner, the condensation of the steam creates a vacuum which is held by the vacuum vent valve as described in Chapter 13- This valve*while permitting air to escape from the systeny pre vents the air from re-entering. As the vacuum is increased and the absolute pressure in the system be comes less, the water continues to boil. The source of heat for the boiling is the heat stored in the water itself and the metal of the boiler. For example, at 1 psig the boiling temperature of water is 215F, while at 10 inches of mercury vacuum the boiling temperature is only 192F. At 20 inches of vacuum, the boiling temperature drops to l62F. Once the space is heated and the air expelled, the system stays full of steam but at progressively lower temperatures until the burner is re cycled. At that time there is a uniform increase of pressure throughout the system, a correspondingly uniform increase in steam temperature in all the radiation and even distribution of heat to the space. Usually on the second and subsequent burner cycles, the thermostat is satisfied before the steam pressure gets above atmosphere. However, the vacuum vent valves are not absolutely tight.- During a twenty-four hour period air leaks into the system and the vacuum is gradually destroyed. On morning pick-up of the space temperature the burner is on a suf ficient time to once again develop stream pressures above atmosphere and cause the expulsion of air from the system. Page 17-1 10700 Vapor systems may be identified from the following; 1. Packle6s steam valves installed at the top of the radiation. 2. Thermal traps on the radiation. 3. Vacuum vent valves on the dry returns. 4. Boiler return trap usually used. See Chapter 13. The Vacuum System In the vacuum system the boiler and supply mains operate under pres sures above atmosphere. The return mains--and sometimes the radiation-operate under a vacuum created by a pump which removes the air from the system--and discharges it to atmosphere. The same pump also acts as a condensate pump returning the condensate to the boiler. Pressure on the supply side of the system vary from 1 to 10 psig and vacuums on the return side are held at approximately 10 inches of Hg. Packless valves are employed on the radiation. These valves installed at the top of the radiation may be adjusted to vary the steam delivery to the radiation and the heat delivery to the space. The Subatmospheric System The subatmospheric system, which is a vacuum system, is designed to provide modulated heat input to the space. Heat output from the radiation is controlled by varying pressure,tem perature and specific volume of the steam. Unlike the vacuum system with the vacuum primarily on the return side, the subatmospheric system has a controllable vacuum maintained on both the supply and return by a pump. Pressures in this system may be in excess of atmospheric in severe winter weather and vacuums of as much as 25 inches may he maintained in the system during mild weather. When heating of domestic hot water by the boiler is required, the boiler operates at sufficient pressure to satisfy the domestic hot water demand. Steam to the system is supplied in modulated quantity by thermo statically controlled floating type steam valve on the main. If the boiler is not required for domestic hot water, steam genera tion may be thermostatically modulated "by controlling the burner. Radiator supply valves may have adjustable orifices in them. In some systems orifices are omitted. The thermal traps are designed to operate from 15 psig to 26 inches Hg. Some of these systems are proprietary. Page 17-2 V . r, ' 10701 STEAM BOILER MANIFOLD SIZING I * . r, 10702 CHAPTER 18 STEAM BOILER MANIFOLD SIZING Steam boiler manifolding is important. Manifold boiler connections must be large enough to restrict steam velocities to 60 feet per second or les6. At the same time, oversized manifolds and boiler connections add unnecessary costs to the installation. For any boiler being fired at it6 specified rate, the velocity of the steam leaving the boiler depends on the size of the connecting piping. Obviously, to carry the same amount of steam, a four inch pipe will require higher velocities than a six inch. Steam velocities higher than 60 feet per second are to be avoided because; 1. Noisy steam flow 2. Steam carries entrained water particles out of boiler -- is wetter 3. Increases possibility of priming or slugging 4. Greater chance of water hammer with unnecessary water in the mains. In the larger sizes of sectional cast iron boilers, multiple outlets are desirable to maintain a uniform water level. For example, if steam were taken from one end of a long boiler, the steam pressure at the end of the steam outlet would be lower than at the opposite end. The water in the boiler would behave as in a U-tube with the level sloping upward toward the 6team outlet end. The possibility of priming, slugging, or other erratic operation is prevalent depending on the location of the low water cut-off and boiler feed control. All of these factors have been considered in the design of the recommended piping arrangements shown in the Technical Catalogue Bulletins issued on AmericanStandard boilers. The pound rate-of-flow of dry or nearly dry steam through a pipe is deter mined by the size of the pipe and the specific volume (cubic feet per pound) of the steam. The basic flow equation is; Volume r Area x velocity To determine the proper pipe size the above equation is re-written; Volume Area = Velocity Where; Area is expressed in square inches Volume is expressed in cubic inches of steam per second Velocity is expressed in feet per second v * ,,1 Page 18-1 10703 We knew that about 1,000 Btu per hour or 1 Mbh of gross boiler capacity i6 equivalent to the heat required to produce one pound of steam at 1 psig and a standard barometer. A pound of steam under these conditions occupies approxi mately 25 cubic feet. To substitute properly in the basic equation; Volume in cubic inches per second Mbh x 25 x 1728 3^00 Mbh x 43,200 555o Velocity in inches per second Velocity in ft./sec. x 12 Substituting the values for volume and velocity in the equation; Area = Volume Velocity Area in square inches Mbh x 43,200 Velocity (ft./sec.) x 12 x 3600 Mbh x 43,200 " Velocity (ft./sec.) x 43,200 Mbh_______ Velocity (ft./sec.) Example 1 Determine the size of the outlet piping from a steam boiler with a gross capacity of 1,000,000 Btu per hour (1,000 Mbh) at a steam velocity of 55 feet per second. The total cross sectional area of the outlet piping in square inches equals ^ " l8.l8 square inches Referring to Table 18-1 it is found that one 5" outlet has 20.00 square inches of cross sectional area or two 3?" outlets have a total of 19*78 square inches of cro66 sectional area. Either one 5" pipe or two 3^" pipes i6 adequate. Page 18-2 f 11 10704 Example 2 What size piping is necessary to handle the steam flow at 60 feet per second velocity from a G-6013 boiler with an output of 1,392 Mbh? The equation is; 1392 Area " "23.2 square inches From Table 18-1 it is found that a 5" pipe has 20.00 quare inches of cross sectional area and , a 6" pipe has 28.90 square inches of cross sectional area Therefore, the 6" pipe is used. Example 3 If the six inch outlet is installed what will the actual steam velocity be? Transposing the equation Mbh Mbh Area" Velocity to Velocity-^ to Velocity = 48.57 feet per sec. Table 18-1 may be used directly to determine the size of the steam out let on piping. Example 4- An 710-S0 boiler has a gross I:B=R rating of 1,760,000 But per hour. It also has four 4-inch flow tappings. If all four flow tappings are connected to a header, what will be the approximate steam velocity through each. Dividing 1,760,000 Btu/hr. 4 flow pipes 440,000 btu/hr. per pipe Referring to Table l8-l on the 4-inch pipe size line, it is found that at a velocity of 45 feet per second a 4-inch line can handle 572,900 Btu per hour. Obviously, four flow connections are very 6afe. They are also more costly to make. Page 18-3 10705 Let us try three four-inch supply connections to the boiler. Each fourinch line will carry 1,760,000 3 or approximately 586,700 Btu/hr. The vel ocity (Table 18-1) is slightly greater than 4-5 feet per second. Three S^-inch supply connections could be used with a load of approximately 586,700 Btu per hour and a velocity under 60 feet per second. Several sizes of manifold can be selected depending on what steam velocity is desired. (Table l8-l) The total load is 1,760,000 Btu per hour. 6-inch manifold---- velocity under 60 feet per second 7-inc'n manifold-----velocity under 45 feet per second The most economical combination becomes; Three 3i~inch flow connections to the boiler One 6-inch manifold. M ^ * f< f Page 18-4 10706 o -Q Eah) %oo O u o ----- Square F e e t o f R a d ia tio n o U"\ 5$ ON 3 r-1 oO Oo -4 OJ 04 OOJ CO Of 888 m NO rH o o -4 c- ^k k 8voO rH on on on ON ON la O CO OJ OJ -4 -4 ON NO LA c*-- CM 8 8 ON CO n m \o 43 CJ 9 OJ a` CO CD o LTN LA O o O r- On ON NO *--( O c-- O VO CM On NO k rH rH Cc--M CM -4 -4 rH CM O Q oo O o LA o c-- k c-n NO on v rH H CO NO rH rH rH OJ 4>3 t +3 H Cm OP OQQ O <5 O NO k -0s NO oO oO t-- CM S O oO 0 oo m ON ON w n oo oo OJ o l O LA rH LA 8 on NO 8 on -4 8 8 m m r*- 4" H rH co rH a> > d 43 rH OJ -d- LA t- rH s CO s cO s -4 s m pa OJ OJ 4* NO a> V CO Ooo O Oo o -4 NO LA o vLOA NO LTN LA NO NO OJ OJ * o o o On * on rH rH OJ 8888 o -4 c-- m LA s s LA ON ON -d- NO NO on NO On m OJ cn -d- NO 88 8 8 IA H on 0 rH CO On O -4 -4 LA LA Co*-- -r4- s OJ o CA 8n NO CO LA o CO LA LA m CO CO on k CM O oo oQ % o -d- V o NOn 3 *k O LTN >k on LA ON LA rH rH CM o55 8 LA Cs LA LA OJ -4 CM -4 rH rH on -4 C~- LA OJ on -4 IfN rH 88 c-- CM NO ON O C-- VO CM ro NO rH CM 8d OJ NmO u ON r- ON ON m eo O c-- 8 8 CM o NO < on -4 t"-- ON CM o 00 & rH CM CM CO rH H a CM H? m on m NO CO OJ H OJ H a u QJ > OJ CJ oj N H (0 S. b0 H f~ ft fCDt iH-1-d- O T3 43 rH t3 T) U << dg OJ 3 43 UJ +3 c u CD M M d OJ --' -w LQ CO y J a. P, Pk OJ CD uft 03 C 0) rH CuJ Lf-t. -p U a} CJ 0) +3 ud bfl OJ u p bo < 43 d 0) a a "d* 03 +3 (0 OJ rO 43 0) pft rH 0) -P o o bO d 3 CJ u H OJ PCOi o o 73 CJ o t) +3 < < U +3 O (0 dp +3 OJ ft d p P +3 d o 60+3 CJ to A Ato <A0 o 0) P& a OJ (0 o OJ o -H o <H to to C-i H OJ 43 44O33J o u o> d 0) S*? jC 4f H ^ CD D Page .18-5 10707 HOT WATER-FORCED CIRCULATION 'i ^ 1 ft1 10708 CHAPTER 19 HOT WATER -- FORCED CIRCULATION There are gravity feed hot water heating systems, but they are found only in residences in older systems. Forced circulation is used in all large hot water heating systems. They are rated in two different categories, depending on water temperature. High temperature hot water systems operate above 250...usually 300 or higher and require high pressure boilers. We will discus^ in this chapter, low temperature hot water (LTHW) systems operating below 250. These systems also fall into two basic classifications according to whether they use one or two pipes as mains. However, sometimes both basic piping arrangements are used in the same system...two-pipe systems can be either direct or reverse return...and some times a "series loop" is incorporated in the,system. So, there are four terms describing piping arrangements for forced circu lation hot water systems: 1. One-pipe 2. Two-pipe (reverse or direct return) 3. Series Loop 4. Combinations of items 1 through 3 One-pipe 'i f' Page 19-1 10709 The one-pipe system i6 often the least expensive piping arrangement for large hot water systems. It6 major problem is the drop in water tem perature around the circuit. On carefully designed systems the water temperature drop is readily estimated and radiation sized for its average water temperature. Two-Pipe FIGURE 19-2 The two-pipe reverse return system with the water flowing in the same direction in both the supply and return mains provides an inherent balance. In general, the distance the water must flow from the boiler to any one radiator and return to the boiler is the same as the distance to and from another radiator. i- 1 j 1 1 Page 19-2 10710 ZONE VALVE ^ BALANCING VALVE I -------. _____ -^4_ t -SUPPLY RISER i K-RETURN j RISER FIGURE 19-3 In some large systems the circuits connected to the supply and return risers perform as though they vere on a two-pipe direct return system. For best operation the circuits should be installed with balancing valves to prevent possible short circuiting and insure the delivery of proper water quantities to each. Zone valves may be installed on each circuit in addition to the balancing valves, when thermostatic control is desired. This circuiting is adaptable to apartments. 'i * - ?, Page 19-3 10711 FIGURE 19-4 Figure 19-4 shows a combination of a two-pipe reverse return system in the basement, with a two-pipe direct return riser arrangement and series loop circuits for baseboard between the risers. Thi6 circuiting is adapt able for apartments. Balancing valves are needed on each circuit to prevent short circuiting. When thermostatic control is required^ zone valves on each circuit are used with the balancing valve. 1 W i f, > Page 19-4 10712 HOT WATER-SIZING AND LOCATION OF PUMP CHAPTER 20 HOT WATER -- SIZING AND LOCATION OF POMP Proper pipe-sizing in large hot water systems will help to guarantee these two important items in any heating system; economical installation and reliable, trouble-free operation. In this chapter we will discuss only LTHW...lcw temperature hot water... defined by the American Society of Heating, Refrigerating and Air Condition ing Engineers as "any temperature up to 250F." Hydrostatic pressure...the pressure created at the base of a column of water by the weight of the water itself...is a consideration in hot water system design. From Chapter 2 "Fundamentals of Pressure".-------- 1 ft. of water .433 lbs./sq. in 1 lb./sq. in. 2.31 ft. of water 1 lb./sq. in 27*72 in. of water Example 1 An American-Standard boiler is to be installed in the basement of a six-story building. The highest piece or radiation is 65 feet above and 100 feet to the west of the boiler. The lateral distance is not a consideration. Only the height of the water affects hydrostatic pressure. Therefore, since 1 foot of water equals .433 psi, 65 feet of water equals; 65 x .433 psi or 27.1 psig Example 2 In the same system, the fill line to the system is connected at the boiler. To what pressure must the reducing valve on the fill line be adjusted to pro vide a pressure of 5 psi La the topmost piece of radiation? The pressure at the point of fill must equal the hydrostatic pressure plus the pressure at the topmost piece of radiation...or 27.1 psig-f- 5 psig... or 32.1 pounds per square inch gage. The reducing valve must, therefore, be adjusted to supply against a pressure of at least 32 psig. Example 3 What theoretical height of system measured from the boiler to the highest piece of radiation will an American-Standard boiler fit when it is designed for 50 psig pressure when 5 psig pressure is required in the topmost radiator? Page 20-1 'i 10714 Deducting the radiation preseure from the total pressure, the boiler can withstand 4-5 psi in hydrostatic pressure. Since 1 psi will support a column of water 2.31 feet high, 4-5 psi will support: 45 x 2.31 or 103.95 feet of water Pumps All large hot water systems are mechanically circulated .by a pump. In heating systems the head -- or pressure -- of the pump is expressed in feet or the height, to which it will pump water in an open system. Another way of 6aying it is that the feet-of-heaui of a pump is equal to the height of a column of water that creates a hydrostatic pressure equal to the difference between the water pressure at pump suction and pump discharge. l. 0. FIGURE 20-1 The difference in height between A and B, measured in feet, is the head of the pump. Standard design practice today is to drive hot water heating system pump6 by direct drive from the motor...sometimes with a flexible coupling between motor and pump shafts. 'I V ' 1 Page 20-2 10715 This means that pump speed is equal to motor speed. For any given motor the pump has one characteristic performance curve which plots the pump's ability to create a pressure in feet of head related to the number of gallons of water per minute circulated. For any one pump, the pressure (feet of head) at which it pumps will decrease as the amount of water it pumps ' increases. This characteristic i6 common to all centrifugal pumping devices. O 10 20 30 40 50 60 70 80 DELIVERY IN GALLONS PER MINUTE FIGURE 20-2 This is a typical pump characteristic curve. Assume that a pump with thi8.performance curve is being considered for a Job designed for a 20F temperature drop with a 300,000 Btu/hr heat loss. The minimum number of gallons per minute of water required is established by the equation; Btu/hr = (gpm x 60 x 8-1/3) x (1 x 20) = gpm x 10,000 where; Btu/hr * heat load gpm minimum gallons per minute required 60 * 60 minutes per hour 8-1/3 * 6-1/3 Its. of water pergallon 1 *= specific heat of water (Btu per pound per degree) 20 therefore; " 20F temperature drop in system 300,000 " gpm x 10,000 gpm " 300,000 -f 10,000...or 30 Page 20-3 '! W . r, * 10716 DELIVERY IN GALLONS PER MINUTE FIGURE 20-3 How...entering the base line at 30 gallons per minute, a vertical line i6 erected until it meets the curve at A. A horizontal line from A, on the vertical scale, will show the feet of head .available from this pump. Small System Pipe Sizing In small systems for residences and'small'commercial buildings,it is good practice to select the pump, determine the head it will deliver when circulating the minimum quantity of water, then size the piping against this head. Since pipe-sizes are ho larger than 1-1/2" and resulting water velocities are less than the critical 48" per second, this procedure.works well. Large System Pipe Sizing On large systems, where pipe-sizes exceed 1-1/2 inches, piping is sized on the basi6 of pressure drop per foot of equivalent length at water velocities that will assure quiet flow. ( A safe and practical rule of thumb is to assume that feet of equivalent length equals 1-1/2 times the feet of linear length. Resistance in each pipe-size-segment of the system is calculated separately by multiplying the equivalent length in feet by the resistance per foot. They are all added together to establish the total resistance of the system. The pump is then selected which will have a head, equal to or greater than the resistance of the circuit while circulating the minimum water re quirements of the system. - Page 20-4 ' I V i [, \ 10717 DELIVERY IN GALLONS PER MINUTE FIGURE 20-4 As a demonstration, assume a system requiring the circulation of 50 gpm against a friction of 14 feet of head. This point is plotted at point "C". Friction head for other circulation requirements can then be determined by the formula: friction varies as the square of the velocity...or, as the square of gpm. Dropping a vertical from "E", where the friction curve intersects the characteristic curve of pump A, indicates a circulation rate of only 46 gpm. To be safe, we must specify pump B with a surplus capacity (52 gpm). of course, in practical usage, it is only necessary to establish point "C". Always specify the next larger pump rather than an undersize. The total resistance of the circuit includes friction loss through piping, fittings and the boiler. ' Recent studies by pump manufacturers have demonstrated that placement of both pump and expansion tank on the supply side of the boiler is more de sirable . Page 20-5 10718 Figure 20-5 Figure 20-5 shows a schematic drawing of the pressures in a hot water system with both pump and expansion tank on the supply side of the boiler. The solid line ABCD indicates the constant pressure level throughout the system with the pump idle. When the pump starts up, there is a slight pressure drop at I, the pump intake, and a rise to E at pump discharge. The difference between E and I is the head of the pump. The line JE shows the pressure increase in the system when the pump is running. From E to F the pressure decreases due to friction in the piping. This loss continues around the circuit through G, H and finally to A, where the pressure is equal to system pressure whether the pump is running or not. Page 20 -6 i v ' (,< 10719 With the pump in this location, the lowest pressure is at I -- the pump suction. Assuming a pressure of 15 psig with the pump not running, then pres sure at I, because of friction, will be only slightly below 15 psig -- maybe 14.9 or 14.8 psig. Still well above the atmospheric pressure. B G Figure 20-6 But! With the 6ame pump on the return side, sucking water around the circuit instead of pushing it, the pressures change. The solid line ABCD again represents system pressure with an idle pump. A, at the expansion tank, is the constant pressure point in the system. Page 20-7 M 10720 Again, the lowest pressure is at the suction end of the pump (H). Going backwards around the circuit, the pressure is higher at each succeeding point G, F and E because the pump is pulling rather than pushing and lowering pres sure constantly around the circuit. Note that pressures all around the circuit, now, are lover than the pres sure in the system with the pump not working. With a low head pump in the same 15 psig system, pressure H might be as low as 11.8 psig instead of the 14.9 or 14.8 psig with the pump on the supply side. While 11.8 psig is still substantially above atmosphere and would operate the system satisfactorily, trouble would arise if; 1. The system static pressure fell too low 2. The pump had a high head For either or both of these reasons, pressure at pump suction point H might fall too low. This situation could, set up two problems: 1. If pressure fell below atmosphere, the pump might suck air into the system around the shaft seal which i6 designed to hold water but will let air in. 2. The pressure might fall low enough to cause the hot water to flash into steam...creating noise a6 well as damaging the pump. The relation between pump and expansion tank location is not important normally In residential systems, because pump heads are low. In large hot water systems with high pump heads, safer, more dependable and quieter operation demand that both pump and expansion tank both be lo cated on the supply side of the boiler. Except in noi6y factories, piping is always designed for quiet operation, which means air-free water traveling through the system at less than 4 feet per second. Table 20-1, showing gallons per minute, indicates design limits in pipe size and friction for quiet operation. Gallons per minute can be converted to Btu/hr. by multiplying by 10,000 for a system designed for a 20 drop, 5,000 for a 10 drop. Friction i6 expressed in milinches which are equivalent to a loss of pressure equal to a column of water l/l,000ths of an inch high. One foot of head, then, will overcome 12,000 milinches of friction. M V ' n' Page 20-8 10721 TABLE 2 0 -1 heavy lin e s w i l l provide noi6y water flo w . For values fo r 5 and 6 Inch pipe in q u ie t zone, re f e r t o ASHRAE GUIDE. o Lf\ o o CM coon o CO CVJ CVJ CVI -4 H CM o OvA A r- -4 O -4 r- A oOV rH rH CVJ -4 on fc- oLT\ CVI t-- CVI -4 CD o ovCVJ CVJ CVJ CVJ -4 vo Ov rH CO On on vo CVI VO H rH cvj j- rH CM -4 t*- o on o on on4 -4* CVJ cvj CVJ OV Ov onCVJ oj -4 CM r- cvj m -4* CO A QJ rH rH A rH CM -4* CO acCvMj CM LCVAI o o rH cLvAj rH rooHn C-o4On- vCroO- roHn rH 0-40 rH -mo4n Ar- A CaoVJ on cOv'j- o LA C-- o vrHo rH o covnj CHVJ A oOmen Oonv rH A rH NooOnn o VrOH SArC--VI m co cO on LA OJ rH Ov VO A oonn rH -4- A o 0O0V -t4" rH CVJ c-o4on OJ vo onon 4 on LA cvj LA rH rt--- rH on Aon VO A om rH on VO CVJA rH rH -Co4VJ VCCOM- rcirvn\j 4 CO on LA CM CM rH cVHOo* voron- -O4N- A CoO rH NrHO rH vCCVVoJJ -Cr4HVJ cAo- oiornv LA CM on VoO* CCOM rH -O4Ne- rH cooonn VCoOVJ on rH CNOO rH rH VCoOVnJ -o4 cAo--n Aro--n VO mm CM VO* CVJ m rH CroHM tOo-nv v-C4oV**I t-- rH rH Ac*- rH -CA4VJ vo -A4 N-t4O- sQ4O VO 4 -4" m vo* co--n rH cCO--M o -r4H* NNrHOO rH 3 rH m CAVJ CrV-J CoOv- &CL4TMV LA 0- CM m vo -4- rH LA rCHM v-C4oM- NCCOOO vCoM rH COr rH vccovvjj -4 CoCOVJ oa4 c-- H t"- On C*-- on NO -4" rH rH oCMj o 4-4* otH-- Ov Oonn rH rH cvj- oA A A 3 AC4*- CO 00 on LA rH C0CVMJ- on -A4" Hcon- omn rH COON rH <C8VI CrHVJ A CCrVO-J a8 CO a Ov on on -4LA -4" oCVnJ A V-4O" Ar- on rH CmoVI CCOVOVJ ot-n A CO oLLAA o\ 4 t~*" V-4O* -rC4M*- -Oo4*v 4 OC--9v --44 rH A CrHVJ omon VtO- A -OA4-v Oo CoVI -m4 CO CC"M-- rH Ov CLVAJ CVJ rH A 0om0n o A rH vCCoVVJI CooVnJ Aov A COOVVJv # Hdtt cvi rH >-m>4s> H -4* rH CVJ 1rH rH CVJ CVJ Hcvlj cvj m mH1 -4 A vo rH O Xi oa rPaH oj rH w ogo0u) s, JOcdoJ rcH CO +a33> Ca(0O> ca -rOoHp O>J S0h) >a Ou o0) 5H OidJ O0>) +a0>) w0) * Page 20-9 10722 Consider a 2" pipe. The table indicates that it can handle 4l gpm at a milinch friction of 400 per foot of length. If it is asked to carry 42.6 gpm, milinches of friction rise to 425 per foot of length and water velocity exceeds the permissible limit of 48 ft/sec. Similarly, the safe, quiet loading of a 2-1/2" pipe is 59.4 gpm; for a 3" pipe, 93 gpn- Note that a6 pipe size increases, allowable friction for quiet operation diminishes. This table can be used to specify pump size. Por instance, the system will use 265 feet of pipe. By rule of thumb we multiply this by 1-1/2 to get 397 -- or 400 feet of equivalent length. Requirements are for 40 gallons per minute. The smallest pipe that will carry 40 gpm is 2" and it will set up 400 milinches of friction per foot. 400 milinches X 400 feet - 160,000 milinches of friction. 160,000 -5-12,000 - 13-3 feet. A pump with at least 13*3 feet of head is required, for a circu lation of 40 gpm. Two or more pumps in series in the same circuit are not frequently used. Since their heads are additive, the effect on the system is that of a single large pump having a head equal to the sum of the heads of the two smaller ones. When the quantity of water to be circulated is small and the head require ments are high, two small pumps in series may be more economical to install than one large one. A small but growing practice uses two pumps in series but in separate zones or circuits of the same system. This arrangement is called primary and secondary pumping. Primary and secondary pumping for zone control is relatively new. It has certain advantages. 1. A better degree of control is achieved than with motorized valves. 2. Pump and pipe sizes can be reduced by allowing for greater temperature drops in the primary circuit. 3. Hydraulic and heat balance is achieved with economical operation. 4. Total pumping horsepower is usually less. 5. Continuous water circulation with modulated temperatures and heat delivery to the zone is possible. 6. Installation costs are frequently less than other control systems. Page 20-10 'I. 10723 FIGURE 20-7 Figure 20-7 illustrates a basic piping arrangement for a system using primary and secondary pumping. Its principal of operation is simple. When a secondary circuit is connected to a primary circuit, such as in a one-pipe system, the resistance created in the primary circuit between the supply and return tees will cause a water flow in the secondary circuit. However, when two ordinary supply and return tees are placed close together on the primary circuit, the resistance becomes so small between them as to cause almost zero circulation in the secondary piping. With this piping arrangement, pumps may be selected to overcome the resistance of each of the two circuits. The primary pump operates continuously. The secondary pump is put under thermostatic control to supply heat to the zone needed. FIGURE 20-8 Figure 20-8 illustrates the development of multiple zoneB from the basic diagram in Figure 20-7. Page 20-11 I V i f 10724 The primary circuit performs similarly to a one-pipe system and is nor mally designed for a 20F temperature drop. When temperature drops of more than 20F are used, the radiation must be selected on the basis of the average vater temperature available at each zone. FIGURE 20-9 Primary and secondary pumping may be used with either a two-pipe direct return or a two pipe reverse return primary circuit. The reverse return arrangement is preferred as shown in Figure 20-9. FIGURE 20-10 FIGURE 20-10A In all of the previously described arrangements the secondary pump is operated intermittently. Figure 20-10 illustrates an arrangement for continuous pump operation in the zone with a two-way (open - close) valve, thermostatically controlled, that admits hot water from the primary circuit. The zone still gets heat in 6hots. Page 20-12 M\ 10725 An identical effect can be obtained with a three-way (open - close) valve. See Figure 20-1QA. OWE PIPE PRIMARY OR FIGURE 20-11 FIGURE 20-11A When modulated water temperatures are desired for continuous heat delivery to the zone, the piping arrangement illustrated in Figures 20-11 and 20-11A are required. Modulating valves, either two-way or threeway, are under thermostatic control. Page 20-13 i 10726 HOT WATER SIZING THE EXPANSION TANK V i f 10727 CHAPTER 21 HOT WATER -- SIZING THE EXPANSION TANK Tanks are necessary in hot vater heating systems to allow for water volume expansion as it is heated. Economical sizing of this component as well as others is important to the sale. Originally, open expansion tanks were used above the highest piece of radiation. They allowed for water expansion but had no effect on system pressure. Modern tanks are closed...containing about 60$ water and 40$ air. As system water expands it moves into the tank, compressing the air cushion and raising the system pressure. Water logged tanks...insufficient air...cause too great a rise in system pressure...spitting by the relief valve and the necessity for replacing the lost water. Factors governing the sizing of expansion tanks are the same for all systems. They are: 1. The system volume of water 2. Maximum average water temperature 3- The fill pressure of the system 4-. Tank location in the system However, small system tank sizing is commonly accomplished by allowing one gallon of tank capacity for each 5,000 Btu/hr of heat loss. This "rule of thumb" does not work for large systems because of the greater importance of the four factors listed above. In the guide published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, tank volume is determined from the ASME equation; (,0004lt - .0466) vt Pa ?& x vs Pt Po This equation assumes expansion tank temperature of no greater than 70F. where; Vs t Pa Pt PQ Minimum gallonage of the tank " SyBtem volume in gallons " Maximum average water temperature in F Absolute pressure in tank when water first enters... usually atmospheric (14.7 psi at sea level) " Absolute pressure in tank created by initial fill... psig fill pressure plus atmospheric " Maximum absolute operating pressure...maximum psig pressure at tank plus atmospheric Page 21-1 V 1 r, 1 10728 To develop a similar working formula ve will substitute "C" for the first factor in the right hand 6ide of the equation...for sea level conditions. Vt C x Ve where C= ,0004lt - .0466 Pfl. Pa ?t Po Let's 60lve for C; t -230F Pa - 14.7 pel absolute...atmospheric pressure Pt26.7 psi absolute. ..12 psig initial fill pressure Po"59*7 psi absolute.. .45 psig maximum operating pressure then C" then...if; .0004lt x 230 - .0466 ------- ---------------W7j--------- 2577 ' 59.7 ` -157 Vt " C x Vs and...the specified system has a volume of 9^0 gallons Vt - .157 x 960 or 150.7 gallons EQUALIZING CONNECTION FIGURE 21-1 To supply an expansion tank volume of 150.7 gallons, it would be common to pipe three tanks in parallel. Page 21-2 1 V . (, 10729 The tables in this chapter vill supply the information necessary to easily and readily determine expansion tank size. Tables 21-2 through 21-6 specify gallonage in different segments of the system. Simple addition will establish VB...total gallonage in the system. Table 21-7 provides factors for C under varying pressures and temperatures. Simple multiplication of the established system volume by thi6 factor will determine the minimum size of the expansion tank. When expansion tanks are located in an area where the temperature may become considerably more them 70F, the ASME equation must be corrected for the following reasons; 1. The air cushion becomes hotter. Since the air has no place to expand, its pressure increases. 2. The hotter water in the expansion tank causes additional vapor or steam to mix with the air cushion. This action increases the pressure on the water in the tank and, hence, the system pressure. The corrected factor C becomes; C where; .0004-lt - .0466 Pa__ T-tx_ivPt Pvf Tf P0 - ?vt t - Maximum average water temperature in degrees F. Pa "Absolute pressure in tank when water first enters.. .usually atmospheric Pp -Absolute pressure in tank created by initial fill. PQ "Maximum absolute operating pressure. Pvf Absolute vapor pressure in psi at the fill temperature. Pyt Absolute vapor pressure in psi at the tank operating temperature. Tp - Absolute temperature of the tank at operating conditions... 460 plus degrees F. Tf "Absolute temperature of the tank at fill conditions...460 plus degrees F. To illustrate the effect of a heated tank, it is assumed the system was filled at 40 F. With the system in operation the tank temperature gets to 125F. All other conditions remain the same as in the example immediately preceding. Page 21-3 v 10730 Solving for C t = 230F Fa 14.7 psi absolute--atmospheric pressure Pt = 26.7 psi absolute--12 psig initial fill pressure P0 m 59*7 psi absolute--45 psig maximum operating pressure Py 0 *122 psi absolute at 4oF tank temperature. See Table 21-1 P^ 1.942 psi absolute at 125F tank temperature. See Table 21-1 Tt = 585 Absolute--460 + 125 - 585 Tf >= 500 Absolute--46QO 40 500 .00041 x 230 - .0466 cs 157? 585 / 157? " - .122) ' 5S0 x 59.7 - 1-942 -1S6 Therefore under these conditions V+t - .186 x Vs,, for a specified system volume of 9&0 gallons Vt .186 x .960 179 gallons Because the tank operates at a temperature of 125F -- all other conditions in the two examples remaining the same -- its volume must be increased 19$. Warning This percentage increase applies only to the conditions in the examples and should not be used for other operating or fill pressures. To illustrate the use of the tables a three-story garden type apartment with a boiler in the basement requires 390*000 Btu/hr. The linear feet of N85-L Heatrim installed is 550. Linear feet of piping in the installation is: 2" pipe -- 50 ft. 1-1/2" pipe ---400 ft. 1" pipe ---200 ft. 3/4" tubing---200 ft. (not including radiation) Page 21-4 10731 Boiler used is a G-4010 Volume of water in system Boiler 50 ft. of 2" pipe 400 ft. of 1-1/2" pipe 200 ft. of 1" pipe 200 ft. of 3/4" tubing 550 ft. of 3/4" Heatrim - 77-4 gal. 8.7 " 42.4 " 9-0 " 5.0 " 14.8 " (See table 21-2) II If II <1 21-6 21-6 If ir II 21-6 II 21-6 11 II 21-4 TOTAL 157-3 Assuming expansion tank located in a cool space in the basement and allowing 10 feet between each floor of the apartment building, the radiation on the third floor will be approximately 22 feet above the expansion tank. Using the line showing a minimum height of the system above the tank of 27-7 feet (see Table 21-7) with the corresponsing fill pressure of 16 psig and an average system temperature of 210F, a constant "C" is found to be .16. The expansion tank volume is 16$ of the system volume. Therefore the tank volume is: Vt = .16 x 157*3 gallons = 25 gallons Generally, in large systems, expansion tanks are located in a reasonably cool area making Table 21-7 valid. Should the tank or tanks be located over the boiler, where the heat rising from the boiler will warm the tank, a correction of tank volume for a temperature of 125F should be adequate. Table 21-8 has been prepared to provide correction factors. These factors are applicable only to Table 21-7. They are used as multipliers. Example The value of C used in the problem solved on page 21-5 was .160 as suming the tank was located in a space of 70F or less. If the tank had to be located immediately over the boiler, a new constant "C" must be obtained. At l6 psig fill pressure the correction multiplier from Table 21-8 is found to be 1.20. Therefore the new value of C equals .16 x 1.20 or .192 and the tank volume for the system in the example becomes 157.3 x .192 or 30 gallons Page 21-5 vI 10732 Tank Temperature Degrees F 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 Table 21-1 Vapor Pressure psi absolute .122 .148 .178 .214 .256 .306 .363 .430 507 596 .698 .815 .949 1.102 1.275 1.471 1.692 1-942 2.222 2-537 I V 1 [1 Page 21-6 10733 Table 21-2 VOLUME OF WATER IN GALLONS - AMERICAN-STANDARD HOT WATER BOILERS Sections G-40 G-60 A-5 A-5 3 26.6 4 33.8 57-5 5 41.1 64.0 151 6 48.4 91.5 75-5 167 7 55-5 105.5 84.0 189 8 62.9 119.0 93-0 211 9 70.1 133-0 1 102.0 234 10 77. 146.5 111.0 256 11 160.5 118.5 278 13 225.O 302 15 253.0 17 280.0 19 308.0 21 336.0 22 387.0 25 427-0 28 470.0 31 510.0 33 575-0 37 630.0 4l 685.0 Page 21-7 10734 Table 21-3 VOLUME OF WATER IN CAST IRON RADIATORS AND BASEBOARD Thin Tube (Arco Radiators) -- 8.k gallons per 100 sq. ft. (El) Large Tube Radiators----------------15*25 " """ " " Sunrad - 5 x 20 ............................ 9.00* " ................... -- 7-1/2 x 23 ................... 10.00* " "" Radiantria New Model 8----------------------l8.0 Gallons per 100 linear feet Model 10...................-- 2U.0 * Applies to radiators of 10 sections or larger. For radiators less than 10 sections, multiply indicated capacities by 1.5. Page 21-6 t 10735 Table 21-4 VOLUME OF WATER IN FINNED TUBE RADIATION Heatrim N50 N85 N110 Element --------------------- 1.32 gallons per 100 linear feet " --............ ........ 2.69 " .....................-- 4.42 Temtrim or Similar Finned-tube Radiation 2" Steel tube element ^ in " 11 " 1 ?,i 11 11 11 17.4 gallons per 100 linear feet 70 " " II M II 6;8 " " Table 21-5 VOLUME OF WATER IN CONVECTORS Multifin #4 Element----------------------- .24 gallons #6 " 7/8 " .43 gallons .67 " #10 " 1/12-.......................................................... per 100 inches* per 100 inches "" " Arco #4 Element ----------------------- I.87 gallons per 100 inches* #6 " ----------------------- 2.89 gallons per 100 inches #8 " --..................... 3.84 #10 " ........ ................... 4.85 * Inches of length taken as length of cabinet 1 * > [i> Page 21-9 10736 Pipe Size 1/2 3/4 1 1-1/4 1-1/2 2 2-1/2 3 3-1/2 4 5 6 8 10 Table 21-6 VOLUME OF WATER IN STANDARD PIPE AND TUBE Gallons per 100 linear feet Std. Steel Pipe Copper tube 1.57 2.77 4.49 7-79 10.6 17.4 24.9 38.4 51.4 66.1 104.0 150.0 266.0 419.0 1.21 2.51 4.29 6-53 9-24 16.1 24.8 35-4 47.9 62.2 97-0 13.9 24.3 37.8 I ^ i Page 21-10 10737 Table 21-7 Fill Press. (psig) 12 16 Max. ht. of system above Tank (ft) 18.4 27-7 Value of Constant C (A) Max. temp. 230F (B) Max. temp. ; .148 .123 193 -l60 20 37-9 24 46.2 28 55-3 32 64.7 .242 312 .408 542 .201 259 .338 .450 NOTE: 1. For this table to apply, tank temperatures should 1 no more than 70F. 2. This table is based upon a relief valve setting of 50 p6ig. Smaller size tanks result. 3- Maximum temperature equals maximum system average temperature. 4. For multiple story structures of three or more floors use column B (Max. temperature of 210F). 5- Fill pressure determined by maximum height of system above fill points - 4 psig allowed in highest piece of radiation. Table 21-8 Multiplication Applicable only to Table 21-7 Fill Pressure psig Correction Factor 12 1-55 16 1.20 20 1.30 24 1.42 28 1.65 32 2.14 Page 21-11 i v . j, t 10738 HOT WATER BOILER MANIFOLD SIZING CHAPTER 22 HOT WATER BOTLER MANIFOLD SIZING As in sizing steam boiler manifolds (Chapter 18) it is necessary to re strict water velocity to insure quiet flow. Unlike steam manifolds, there is no fixed velocity limit in manifolds. For pipes two inches and smaller, water flow should be limited to 4 feet per second, while velocities up to 10 feet per second are frequently used in 6-inch or larger pipes. It should be kept in mind that in large systems the mains with the high water velocities are a considerable distance from the radiation where water velocity noise would be objectionable. To arrive at the proper manifold size with hot water boilers,the basic equation is; Volume - Area X Velocity or Volume Area Velocity wnere Area is expressed in square inches Volume is expressed in cubic inches per second Velocity is expressed in inches per second In low temperature hot water heating, the volume is based upon a 0F temperature drop of the system. The weight of one cubic foot of water is taken as 62.5 pounds. '.Vnen cooled 20F it gives up 62.5 X 1 X 20 or 1250 Btu. Volume in cubic feet per hour Btu per hour Mbh 1250 r 1.25 Volume in cubic inches per hour Mbh X cubic inches per cubic foot 1.25 Mbh X 1728 8 1.25 Volume in cubic inches per second = Mbh 1.25 X ---1--7---28 --. seconds per hour Mbh X 1728 Mbh 1.25 X 3600 " 23 Velocity in inches per second equals velocity in feet per second X 12. Puge 22-1 'i t 10740 Therefore, the equation for cross sectional area in square inches becomes: Area * g-g- * 12 x Velocity (ft/sec) Mbh 2.6 x 12 x Velocity Mbh 32 x Velocity or Velocity (ft/sec) Mbh 32 x Area (sq. in.) Calculate the velocity necessary to supply 336,000 Btu through a 2-inch pipe, which has an area of 3-356 square inches. * 107.4 " 3-13 ft/second 6 Table 22-1 has been prepared to aid in selecting manifold pipe sizes on hot water boilers. It may be used as follows. Example No. 1 The G-6022 and G-6028 boilers have respective outputs of 2,436,000 Btu/hr and 3,132,000 Btu/hr. Minimum piping recommendations for these two boilers, as shown in the Technical Catalog Bulletin, specify two 4 inch supply risers and a 6 inch header. Under conditions of maximum output, what water velocities will be obtained? The G-6022 Load per riser = 2,436,000 _ 1^218,000 Btu/hr. Referring to Table 22-1 on the 4 inch pipe size line, it is found that a load of 1,218,000 Btu/hr requires a velocity of 3 feet per second. The 6 inch header, after it has picked up the entire boiler capacity of 2,436,000 Btu/hr is working at velocity of less than 3 feet per second. Page 22-2 10741 The G-6028 Load per riser = 3;132,000 s 1,566,000 btu/hr. Referring to Table 22-1 on the 4 inch pipe size line it is found that a 4 inch pipe with 3-5 feet per second velocity is good for 1,425,000 btu/hr. and at 4 feet per second the capacity is 1,630,000 btu/hr. Obviously, the water velocity is less than 4 feet per second and more than 3*5 feet per second. By interpolation the actual velocity is 6hown to be approximately 3.8 feet per second. The velocity in the 6 inch header after it has picked up the entire boiler capacity of 3,132,000 btu/hr is slightly less than 3*5 feet per second. Velocities in the return header and risers are identical. Example No. 2 The A-710-WO boiler has a gross 1=8^ output of 1,760,000 btu/hr. It is supplied with four 4" flow tappings and two 6 inch return tappings. To carry the full capacity of the boileq how many supply risers and return risers will be required and what manifold size is needed? Referring to Table 22-1 it is found that a 4 inch riser with e velocity of 4 feet per second is capable of handling only 1,630,000 btu/hr. Obviously, it is desirable to use two supply risers instead of one. The load per riser = 1>760,000 = 880,000 btu/hr. From the table it is found that a 3 inch supply riser is good for the 880,000 btu/hr. at a velocity about halfway between 3*5 and. 4.0 feet per second, which is en tirely satisfactory. The header carrying the full load of 1,760,000 btu/hr. must be 5 inches since 4 inch pipe is too small. The velocity in the header will be less than 3 feet per second, again a satisfactory condition. Return risers and manifold will be sized identically. Tappings selected for both supply and return risers must be chosen to provide good distribution of water to the boiler. It is suggested that the FX and first CX sections be used for the flow risers. The returns should be divided between the two 6 inch return tappings (bushed to 3 inches) in the BX sectiun. Page 22-3 10742 Pipe Size Inches 1/2 3/4 1 i-iA 1-1/2 2 2-1/2 3 3-L/2 4 5 6 8 10 I. D. CrossSection Pipe Area 304 .533 .8413 1.496 2.036 3.356 4.788 7.393 9.885 12.730 20.006 28.830 51.162 8l.585 TABLE 22-1 Btu/Hr. Capacity of Steel Pipe for 20F System Temperature Drop Flow Rate --Ft/ S e c 3-0 3-5 4.0 29,200 34,000 39,900 52,000 59,600 58,100 80,700 94,000 107,800 143,500 167,200 191,000 195,500 228,000 260,000 322,000 376,000 429,000 460,000 535,000 612,000 710,000 827,000 945,000 950,000 1,108,000 1,265,000 1,220,000 1,425,000 1,630,000 1,925,000 2,240,000 2,560,000 2,770,000 3,230,000 3,820,000 4,910,000 5,730,000 6,540,000 7,840,000 9,130,000 10,430,000 "I V * f, i Page 22-4 10743 F7 CONVERTORS i ! fr i fl I * 10744 CHAPTER 23 CONVERTORS A convertor is a heat exchanger that is used specifically to transfer heat from steam to water. These units are employed when: 1. A hot water heating system is connected to a steam system with the steam boilers being the initial source of the heat. 2. Steam is purchased from a district steam system but hot water heating is desired. 3- Hot water heating is desired in tall buildings, where the hydrostatic pressure created by the water would become too severe on the piping and radiation at the lower levels. * .2 A excHxA*ANTcra-- in I, 1 i j _ NCAT -- m1 : 1 A fLOO*-? CKChMcAaNtGtH- In Figure 23-1 the method for supplying hot water heating in tall buildings is illustrated. Here the solution is to use one steam boiler in the basement to generate the steam necessary to operate a convertor for each group of four floors. Each con vertor acts as a hot water boiler supplying heat to a zoned four-story segment of the building. Hydrosta tic pressures are brought within practical limits, and only one lowpressure steam boiler is necessary even though it operates three separ ate and distinct heating systems. If g>l i; FIGURE 23-1 The small individual systems thus created use relatively smaller pip ing and less costly pumps and accessories. Page 23-1 fi * 10745 FIGURE 23-2 Figure 23-2 shows a convertor as manufactured by the Industrial Division of American-Standard. The steam enters the top of the shell at the right and fills the space around the water tubes. The water flow ing through the tubes becomes heated and the condensate formed from the condensed steam drains off from the bottom of shell at the left hand end. The water enters one side of the cast iron bonnet flowing through the U-tube bundle and returns to the other side. This flow arrangement is called a two-pass. By rearranging the spacing of the tubes and the partitions cast into the bonnet, a four-pass flow can be obtained. The two-pass flow is advantageous to use because the pressure drop of the water through the heater i6 less than for the four-pas6 arrangement. The U-tube design with the tubes fastened to a tube sheet at one end only of the unit permits a free expansion of the tube bundle. With a steam to water heat exchanger, baffling is not as much a problem as with the water to water type. The round plates 6een in the illustration serve to support and hold the tubes apart so the steam can completely surround them. V i r, ' Page 23-2 10746 FIGURE 23-3 Figure 23-3 illustrates a convertor piping arrangement which is selfexplanatory. In this illustration the thermostatically controlled steam regulator holds the water leaving the convertor at some fixed temperature, in the same manner as a boiler operating on a fixed water temperature. To control the space temperature, the pump could be cycled by the space thermo stat or a three-way valve, thermostatic control by either indoor or out door thermostat can be provided to modulate the water temperature to the space. In this last instance, the pump would operate continuously. Sizing the piping for the system would follow conventional engineered design. The heat loss of the space served by the 6team is determined and a decision made to design for either a 20F or 10F temperature drop. The gallons of water to be circulated is then determined. If the g.p.m. are large, pipe sizes will be selected and the resistance of the piping and fittings determined. To this valve will be added the resistance of the water flowing through the convertor. A pump is then selected that has a head equal t<^ or greater thai^ the total resistance of the system. * u' Page 23-3 10747 CHAPTER 24 SIZING THE BOILER I ! i r, 10748 CHAPTER 24 SIZING THE BOILER To size a boiler accurately for either steam or hot water, its capacity must be equal t<^ or greater than, the load. Either a net installed radiation load or a gross load may be estimated. These requirements can be any or all of the following defined loads; 1. Radiation Load the estimated heat emission in square feetjE. D. R. or Btu per hour,of the connected radiation. 2. Piping Load the estimated heat emission in Btu per hour of the piping connecting the radiation and other apparatus to the boiler. A close approximation for this can be considered at 15# of the net load when 1" magnesia pipe insulation is used. 3. Pick-up Load the estimated load in Btu per hour re quired to bring the space up to daytime temperature following a nighttime set back of the thermostat. This load can also be considered as 15$ of the net radiation load. 4. Miscellaneous Load -- any load other than those listed above such as domestic hot water, snow re moval systems, industrial processes, etc. In residential application it is common practice to size the boiler on the net installed radiation load, since allowances have been built into the net rating of the boiler to allow for pipe loss, pick-up and the heating of a nominal amount of domestic hot water. Where abnormal conditions exist, such as a heavy domestic hot water demand or excessive piping losses, the piping, pick-up, miscellaneous and radiation loads should be added to arrive at the total gross load requirement. The gross capacity or output of the boiler selected must be equal to or greater than the gross load. Page 24-1 V 10749 FIGURE 24-1 Referring to Figure 24-1, it is seen that only a fraction of the heat input to a boiler gets into the boiler water and becomes the boiler's gross capacity or output. In gas boilers that are rated by the American Gas Association this fraction is 0.8 this figure also says that the boiler efficiency is 80#. In oil boilers the fraction varies. It may be 0.7 to 0.75 depending on the boiler and the burner adjustment. The I=B=R net installed radiation capacity of the boiler is about 757' of its output or gross capacity. It is noted that while some of the btu/hr. difference between in put and output is lost from the boiler jacket, the major portion of this heat quantity goes into the chimney. From Figure 24-1 it is evident that the 20,000 Btu/hr. allowed for pick-up, pipe loss and the heating of domestic hot water is about 33-1/3# of the net I=B=R rating. This allowance i6 divided approximately as follows; Pipe Loss----------------------15# Pick-up------------------------- 15# Domestic HotWater-- 3-1/3# TOTAL 33-1/3# Page 24-2 I * I -_f CI 10750 Example No. 1 For examples of these various conditions, let's assume a hypothetical modernization Job involving a boiler replacement. Our problem will be to size a steam boiler in an old four story home of an unknown heat loss. The boiler must be replaced and the owner is desirous of changing from stoker-firing to oil. When the existing boiler is examined, it is found to be an American-Standard Ideal Water Tube S-36-T-7 with a net steam rating of 2,070 square feet. It was common practice years ago to oversize the boiler to insure adequate grate area and sufficient capacity for quick pick-up after long shut-down periods. A further examination disclosed that,by actual count of radiators, only 1,4-70 square feet of radiation or 352,000 Btu per hour was connected to the boiler. Piping and pick-up loss was considered normal because all piping was insulated with 1" magnesia insulation. Based on both loads indicated above, a decision was required to select a size between an A-509S boiler which is equal to or greater than the old boiler size, or an A-507S which wa6 equal to or greater than the net load requirements of the system. Since the owners indicated that the existing radiation maintained good comfort conditions during the 25 years of operation, satisfying the radiation load of 1,470 square feet with an A-507SB boiler is all that is required. The maximum requirements for domestic hot water are esti mated to be 34 gallons per hour. To determine the adequacy of the boiler selected, an analysis may be made as follows: Gross Capacity of the A-507S3 508,000 Btu/hr. Net Load (1,470 sq. ft.) = 352,800 Btu/hr. Pick-up Load - 1% of 352,800 52,920 Btu/hr. Pipe-loss - 1556 of 352,800 = 52,920 Btu/hr. * Domestic Hot Water (34 gph x 833) ` 28,320 Btu/hr. Total Gross Load 11 486,960 Btu/hr. Surplus Boiler Capacity 21,040 Btu/hr. *N0TE: 1 gallon of water heated 100F requires 8-1/3 x 1 x 100 or 833 Btu. Example No. 2 If this same hypothetical house could be made into a multiple apart ment structure by merely inserting partitions and adding bathrooms, with out necessitating any major change in the heating system outside of an isolated relocation of a radiator, then a parallel can be made to the original example, and an illustration of how increased water heater requirements can change the boiler size. Page 24-3 M- 10751 Let's assume the house can be converted into a total of 16 apartments, one bedroom with single bath and kitchenette for each one. The total domestic hot water demand is estimated at 153 gallons per hour. To size the boiler for this example a similar analysis to the one made for Example No. 1 is in order. Installed Radiation (l,L70 sq. ft.) = 352,800 Btu/hr. Pipe Loss (15$ of 352,800) * 52,920 Btu/hr. Pick-up (15% of 352,800) = 52,920 Btu/hr. Domestic Hot Water (153 x 833) = 127,^50 Btu/hr. Gross Load " 568,090 Btu/hr. The gross capacity of an A-508SB boiler is 588,000 Btu/hr. Therefore the eight section boiler would be adequate. Page 2k-4 t . - 10752 c7 SIZING-CHIMNEY AND BREECHING 10753 CHAPTER 25 SIZING -- CHIMNEY AND BREECHING Proper draft in the combustion space of a boiler is of utmost im portance to the satisfactory operation of the burner. Without adequate draft, sooting will occur, efficiency of combustion is lost and noisy burner operation can result. Excessive draft conditions can be as troublesome as insufficient draft. Usually this condition is readily corrected by flue dampers, draft regulators, divertors or these devices in combination. What is draft? Draft is really a difference in pressure exerted by a column of hot gases in a chimney and a column of cold air of the same height outside the chimney. To illustrate, assume two columns, each 30 feet high, and each 1 square foot in cross sec tional area, supported by the pans of a giant balance. See Figure 25-1. Further assume that one column is made up of flue gases at 450F, the other of air at 30F. Each column, then, will con tain 30 cubic feet. Each has a different weight. FIGURE 25-1 Weight per cubic foot Number of cubic feet Toted Weight fpounds) Pressure (lb6/sq. ft.) Hot Gases --row 30. 1.32 1.32 Cold Air ToBT" 30. 2.43 2.43 The greater weight of air would tip the scale, raising the column of hot gases. The degree to which it tips depends on the pressure difference -- in this case 1.11 pounds per square foot. Page 25-1 10754 1.11 pounds per square foot divided by 144 gives .0077 pounds per square inch. Because draft is measured in inches of water -- and 1 pound per square inch equals 27*72 inches of water -- we multiply .0077 x 27*72 to get .21 inches of water draft. This is a very tiny force. Because it is so tiny the boiler room must be open to plenty of air for ready combustion. This .21 inches of water is the theoretical draft available from a 30-foot high chimney when the stack gases weigh .044 pounds per cubic foot and the outside air weighs .08l pounds per cubic feet. The draft would increase if the outside air cooled, or if the gases got hotter or more humid. It would decrease if the opposite occurred. Other factors affecting draft are; 1. The tightness of the chimney. If it leaks, the cold entering air lowers the temperature of the gases and adds to the volume of gases to be vented. 2. The roughness of the chimney lining. 3 Off-sets in the chimney and other obstructions in the path of the gases. 4. Outside air turbulence, either natural on a gusty day or caused by adjacent trees or buildings, may create down drafts. The draft calculated above is theoretical. As the gases start to flow, the friction in the chimney causes a loss 60 that there is less draft at the chimney thimble where the smoke pipe enters. Friction in the smoke pipe and the boiler flues reduces the draft still further so that the draft available in the combustion chamber is usually a very small force. Draft may be classified as: 1. Natural 2. Forced 3 Induced 4. Combinations of two or ail three. Natural draft occurs when a chimney is employed to overcome all resis tance to the air flow into the combustion chamber and the friction of the flue gase6 flowing through the boiler, the smoke pipe and the chimney itself. Forced draft is the case where a fan is used to force the air into the combustion chamber. With gun type oil burners aiid mjchanical stokers forced draft is employed. "I V * f v ' Page 25-2 10755 Induced, draft uses a fan to suck the flue gases through the boiler and deliver them to the chimney, The use of draft booster fans is an example of this type of draft. The U6e of either the forced draft or the induced draft principle re duces the natural draft requirements on a job -- which reduces the required chimney height. Within limits, chimneys may be increased in cross sectional area to reduce the gas velocity and the flow friction through it. If the cross sectional area is made too great for the quantity of flue gases flowing, these gases will not fill the chimney. Air will flow down inside the lining mixing with the flue gases and retarding their flow. The draft will be materially reduced to unsatisfactory levels. When chimneys are too large in area, but sufficiently high, a smaller size liner may be inserted from the top. The space between the new liner and the old must be capped off at the chimney top to prevent oold outside air from circulating down between them. The chimney height is determined by the draft requirements and the area by the Btu per hour input to the boiler. The height and cross sectional size of chimneys required by AmericanStandard boilers are specified in the Technical Catalog Bulletins. Chimneys serving more than one appliance shouM have separate flues for each. Where it is necessary to hook up two fuel-burning appliances to the same flue, they mu6t each have their own 6moke-pipe with the smaller ap pliance connected to the chimney at a higher level. If they are not connected separately, the pipe not in operation may damp off the operating pipe. The smaller appliance should be piped into the chimney at a higher level where Its effect will be minimized. Gas-fired boilers must be equipped with draft hoods to let air into the vent and to divert down-drafts that might blow out pilot flames. The same result is achieved for oil-fired or 8toker-fired coal boilers by installing a draft stablizer in the smoke pipe. Adjustment is made by moving a weight on the damper door. Boilers should be installed with not more than one 90 elbow in the smoke pipe between the boiler and the chimney. If additional elbows or fittings are used, which add resistance to the flow of combustion products within the venting system, the equivalent length of such fittings should be added to the measured length of the venting system. Never use connectors smaller than the boiler flue outlets. Page 25-3 * 10756 A breeching is essentially a manifold. Its prime purpose is to collect the gases from a large boilejj with multiple smoke pipe% or the gases from a battery of boilers and deliver these products of combustion to the chimney. A constant size breeching is recommended. It must be large enough to handle the combined flue gases from all connections to it. The breeching size is usually greater than the chimney, a situation requiring an adaptor, to make the connection of the breeching to the chimney. For example: The problem is to tie a 30" square piece of breeching into a circular chimney with a 20" diameter. Obviously, the breeching mu6t be brought down to a width of 20 inches. This means that in order to main tain the same 900 square inches of cross-sectional area, the 20-inch width will need a 45 inch height. The solution is to add the extra 15 inches in height at the top of the breeching to introduce the flue gas into the chimney in a rising pattern. FIGURE 25-2 When batteries of boilers are 6tep-operated -- one on at a time and one off at a time -- it is advantageous that the boiler nearest the chimney be operating first on the "on" cycle and last on the "off" cycle. This arrangement with properly designed breeching will eliminate the problems of "spillage" of flue gases from one boiler to another. Breeching for more than one boiler should, at a minimum, have the total cross-sectional area of all the smoke-piping for each individual boiler. If the requirements of space or dollars dictate a smaller breeching area, it may be reduced to a maximum of 10$, providing stack height and cross-sectional area are adequate, and a straight breeching can be designed. Breeching sizing i6 based on one square inch of area for each 9,000 Btuh of heat release in the fuel. Page 25-4 ! 10757 Table 25-1 Column B Area Square Inches Column C Equivalent In Rectangular size 113 12 x 10 13 133 12 x 12 14 154 14 x 12 15 177 14 x 14 16 201 15 x 14 17 227 15 x 16 18 254 17 x 16 19 283 17 x 18 20 314 19 X 18 21 346 21 x 18 22 380 20 x 20 23 415 22 x 20 24 452 22 x 22 25 491 24 x 22 26 551 26 x 22 27 572 26 x 24 28 615 28 x 24 29 660 30 x 24 30 706 32 x 24 31 754 34 x 24 32 804 36 x 24 33 855 39 x 24 34 907 4l x 24 35 962 36 x 30 36 1017 38 x 30 37 1075 40 x 30 38 1134 42 x 30 Page 25-5 ` Jt* 10758 Example No. 1 Design the flue headers, manifolds and breeching for tvo G-6022 boilers in s. battery. Heat input = 3,045/000 btuh per boiler o ooq Header & manifold area* ^^qoo-- = 339 square inches Diameter of Header D12 3- , ^22 D - V432 or 21" Example No. 2 Breeching area for two boilers equals twice the area for each header or 2 x 339 or 678 square inches. 'x If the breeching is circular then; D - 29.3" or 30" If the breeching is rectangular, it could be; 32" x 24" To save time, use Table 25-1. Having determined that the breeching area required i6 339 square inches (Example Ho. l) enter Table 25-1 in Column B, going down the column to the area in square inches that is equal to or greater than 339* In this instance the number is 3^ Reading to the left a round manifold of 21 inches is indicated. Reading to the right a rectangular manifold of 21 x 18 i6 shown as being satisfactory. See Figure 25-2 for breeching arrangement. To summarize, helpful hint6 sire listed below. HELPFUL HINTS 1. Always U6e individual vents in preference to combined vents, when pos sible and practical. 2. Never use connectors smaller than the boiler flue products outlet(s). 3. Always make the rise above the boiler flue products outlet(s) as great as possible. Thi6 is especially important when connecting more than one boiler to a single chimney. it,1 Page 25-6 10759 4. Keep the length of connectors as short as possible. 5. Use an inside chimney in preference to an outside chimney, vhen possible and practical. 6. Use insulated vents, when long connections to chimney cannot be avoided. Insulation on the rise from the boiler flue products outlet(s) is par ti cularly important. 7- Eliminate all possible flue turns in the connection to the chimney. Remem ber that vhen more than one elbow is used between the boiler flue products outlet(B) and the chimney, allowance for the added resistance must be made by adding equivalent length of such fittings to the vent system measured length before applying draft loss curves. 8. Never let the connector protrude beyond the inside wall of the chimney nor permit projections into the flue gas passage. 9. Avoid caps on chimney that will restrict the free area of the chimney. 10. "Streamline" the vent system as much as possible -- changes in direction, shape and flow area should be accomplished separately and as gradually as possible. 11. Round connectors are to be preferred over square or rectangular. Square or rectangular flue passa6es sire apt to promote unpredictable turbulence that will interfere with the normal flow of combustion products. Also, flat sides of square or rectangular connectors are more likely to develop noise due to resonance. 12. Lateral connectors should be run horizontal, or with minimum slope per mitted by local code, to keep the rise above the boiler flue products outlet(s) as great as possible. 13. Breechings that connect two or more boilers to a common chimney must be sized to handle the combined load. A 6ingle size manifold of sufficient size for the load should be used. 14. Never connect 2 or more chimneys together to increase flue area available for a boiler Installation. The ASHRAE Guide says "When two chimneys are connected at the bottom, hot gases in the U-tube thus formed would be in unstable equilibrium. Cold air from the top would descend through one such chimney and drive the hot gases out of the other, thus annulling the draft." If 2 or more chimneys are used, each chimhey should be used separately for part of the boilers. Never use a continuous manifold between the chimneys. Page 25-7 1 10760 ^ *5. *5* 10?61 CHAPTER 26 LOCATING THE BOILER 10762 CHAPTER 26 LOCATING THE BOILER There are three possible places to locate a boiler; 1. Below the system...in a basement. 2. Above the system...in a penthouse, on the roof of the building. 3- Alongside the system...in a separate room close to, but detached from, the space to be heated...industrial. Below the System Locating the boiler below the system creates...for any building...the best possible draft condition. Chimney height is at its maximum. For steam systems, the basement is the ideal location because gravity helps to bring condensate back to the boiler, even though, for reasons of fuel economy, a vacuum system using condensate pumps is often specified. Even in tall buildings, low pressure steam boilers operate successfully out of a basement location because steam does not build up high hydrostatic pressures. For any single hot water system, hydrostatic pressures in tall buildings present insurmountable problems. The solution (see Chapter 25) is to use a steam boiler and a series of convertors. Our present line of large boilers, improved from 30 psig operation to 50 p6ig, can be used in buildings taller than for former maximum ca pability. Because of hydrostatic pressures, expansion tanks must be larger as building height increases. Above the System Roof or penthouse systems are rarely, if ever, acceptable for either coal or oil-burning boilers because of chimney height. The use of steam boilers on building roofs is possible but impractical because head requirements on condensate pumps become too great. Because of the help from gravity, low pressure hot water systems can be used in roof installations. In addition, expansion tank sizes are economical. Alongside the System Because of the low chimney height, gas is the Ideal fuel for industrial heating systems, though oil and stoker-fired boilers with somewhat higher Page 26-1 * ' {! 1 10763 chimney requirements axe often used. Hand-fired coal boilers usually present architecturally unacceptable chimney height specifications. For steam systems, the smaller installations can usually be set up to return condensate by gravity. Usually, however, condensate pump6 are used. For hot water systems, industrial applications eliminate the major problems of high hydrostatic pressures and large expansion tanks. Locating the Second Boiler in a Steam System When more than one boiler is used in a steam system, it is imperative that all boiler water lines be at the same level. While the water line problem makes it desirable to use boilers of the same design in new installations, it is not always possible. When, for instance, an estimated heating load indicates the use of a G-oO boiler with a 44" water line plus a G-40 with a 35-l/2*water line... it would be necessary to install the G-40 on an 8-1/2" concrete pad. At times it may be necessary to pit a steam boiler to effect the equalising of water lines. I <, 1 Page 26-2 10764 BLAST COILS AND UNIT HEATERS CHAPTER 27 V"I > .f I I 10765 CHAPTER 27 4* BLAST COILS AND UNIT HEATERS Two types of concentrated heat loads on a boiler are blast coils and unit heaters. In both cases a coil, either steam or hot water, is used to heat forced hot air. The difference is that blast coils are used in duct systems while unit heaters hang free in the space being heated. Propeller type fans are mounted on the unit heaters, either manually or thermostatically controlled, and the air leaving the heater is directed by louver as It leaves the heater. The forced circulation of air condenses steam so rapidly, particularly at start-up of the daily heating cycle, as to create a vacuum in the heater which can suck water from the wet return up into the heater itself. To overcome this vacuum and to insure adequate removal of condensate, steam systems using unit heaters normally carry a condensate pump f ; each heater, or for a battery of heaters. With the heaters installed at a high level, a direct, vertical, drop-leg to the condensate pump allows for fast and positive drainage of the condensate. Unit heaters, for best results, should be operated at a minimum of 2 psig steam pressure at the heater inlet. Where entering air temperature, however, is below freezing, pressure should be at least 5 psig. Pages 27-2 and 27~3 illustrate recommended piping arrangements for unit heaters. Blast coils serve two functions; 1. To temper ventilation air. 2. To supply heated air. In blast coil systems, air is circulated through the ducts by centri fugal blowers. The following pages show piping diagrams for individual blast coils in various systems plus a list of "do's and don'ts". Page 27-1 10766 PIPING DIAGRAMS HORIZONTAL UNIT HEATERS 'x LOW PRESSURE GRAVITY SYSTEM VAPOR OR VACUUM SYSTEM Page 27-2 10767 PIPING DIAGRAMS VERTICAL UNIT HEATERS AIR VENT SUPPLY CHECK. VALVE DIRT TRAP LOW PRESSURE GRAVITY SYSTEM VAPOR OR VACUUM SYSTEM HOT WATER SYSTEM i "i * -.{, i Page 27-3 10768 PIPING DIAGRAMS BLAST COILS Typical piping diagram--apan gravity ly.fam, low pranura .foam-coil tuba. horiioatal Typical piping diagram--opan gravity lytfom, low proituro staam--coil tuba* vortical nTO<iTK C0rOi L< Typical piping diagram --vacuum lyitom, low pm. ura taam--coil tvbai horixontal Page 2J-k f' * 10769 Coll Installation Colls must be accurately Install casings of all heavy duty colls level for either horizontal or vertical air flow. Install coils accurately with a spirit levfcl, not by measurement from building members. Coil Piping Multiple Coil Banks The diagram on preceding pages show the piping arrangements for single coils. The same arrangements should be used on multiple coil banks, the most satisfactory arrangement being to build up the proper system by dup licating the diagrams on each coil in the bank. However, coils in parallel (side by side) or in series (one behind the other) in the air flow may, if desired, be controlled by a common valve. Each coil in a coil bank, whether individually controlled or controlled by a common valve, must have its own trap and air venting system. Provide All Coils with Air Vents On low pressure systems (with steam pressure 15 psig or less) where non-venting traps are used for condensate removal to a vacuum return, a l/2" thermostatic air trap should be located in an air line bypassing the con densate trap. The air line to the trap should be of 1" pipe and the trap located at least 12" above the coil return connection. On low pressure systems where non-venting traps are U6ed for condensate removal to a gravity return, 3/V' individual return line automatic air vents are recommended. These vents should be located at least 12" above the coil return connection and vent to the room. The use of thermostatic traps for air removal is permissible (but not recommended) with a gravity return, provided the return line is vented ade quately to the outside atmosphere. Provide Vacuum Relief A vacuum breaker must always be provided when automatic steam control is used. Under many conditions of operation with modulating control, or when 6team is shut off by a two-poeition on-off control, a vacuum will occur in the coil unless proper relief is provided. The vacuum holds condensate in the coil tubes causing water hammer and, when sub-freezing air is being handled, allows the tubes to freeze. It Is recommended that vacuum breakers also be used with manual, steam control to avoid the possibility of condensate hold-up when the valve is 6hut off. On gravity systems, install a l/2" check valve in a riser at the return connection from each coil. On vacuum systems, install a check valve in a bypass line around the trap to prevent the coil vacuum from exceeding that in the return. Page 27-5 1V 10770 Allow for Removal of Heating Element Make steam and return connections to the coils through an elbow to a union as shown in the piping diagrams. This leaves the coil connection end free of piping allowing removal of the heating element when the unions are diconnected. This procedure is not necessary on Type HA Coils since the heating element is removed from the end opposite the coil connections. Avoid Lifting Condensate and Pressure Returns Lifting of condensate above the coil return into an overhead main should always be avoided if possible and must never be done with automatic control. Temperature control by modulating or by on-and-off automatic steam valves must not be used with systems in which a pressure is maintained in the return lines. Protect Automatic Control Valves, Coils and Traps by Strainers Automatic valves operate much of the time at small openings and are easily plugged by scale and dirt. Each valve should be preceded by a line strainer to assure continuous operation. Each coil should be preceded by a line strainer to protect the supply tube orifices against plugging. If traps are not equipped with strainers, they should be preceded by line strainers to protect their small orifices against plugging. Avoid Rigid Piping Connections All steam and return piping must be provided with swing joints.at or near the heating coils so that piping and expansion strains are not communicated to the coils. All piping should be supported and anchored independently of the heater6. Drip All Steam Lines Steam line condensate should never be passed through heating coils. Steam mains should be dripped from the pressure side of the valve to the return line through a drip trap. Supply branches should be pitched back to the drip ped steam main. Failure to observe this precaution will result in damage to coils through hammer and corrosion. Do Not Bush Return Connections Return piping must be made the full size of the coil return connection from the coil to the manifold or trap. Coil outlets must not be bushed. Piping from the coil return connection should have a vertical cooling leg at least 12" long and a dirt pocket at least 6" long -- all full size of the return connection. Page 27-6 f'' 10771 Traps Should be of Ample Size Blast heating coils should have traps of ample size to handle the high condensation rate of these coils during the starting up period. In general, traps should be selected for 2-1/2 times the calculated coil load. Isolate Colls, Valvc6 and Traps Aside from any question of control, each coil in a multiple coil bank should be provided with a gate valve in its steam supply line and in the condensate line beyond the trap to permit servicing of coils and traps without shutting down the entire system. For the same reason, each automatic control valve should be preceded by a gate valve. Turn Steam On Before Starting Fans Steam should be turned on to heat up coils before air flow is started, particularly when sub-freezing air Is being handled. A 10-minute warm-up period before starting fans is desirable. This will help to reduce the flood of condensate which occurs when steam is suddenly admitted to a cold coil. The possibility of freezing and water hammer due to the coil filling with condensate will thus be reduced. "i v ' fi' Page 27-7 10772 DOMESTIC HOT WATER 10773 CHAPTER 28 CHAPTER 28 DOMESTIC HOT WATER The estimating of domestic hot water requirements for apartments, motels, hotels, clubs, office buildings, schools and the like is open to considerable question. A number of different methods are employed. For example, the manu facturers of commercial hot water heaters usually use a figure of 15 gallons per hour per person. In a motel of 30 twin bed room units, allowing 1-1/2 people per unit, the total hot water requirement at peak load would be esti mated at 30 x l-l/2 x 15 or 675 gallons per hour. Thi6 approach for large apartments, hotels, housing projects and hospitals results in astronomical amounts of hot water, which are not realistic. There are reliable data available, on hot water demand of fixtures, which may be used in estimating connected hot water loads. It is suggested that these demands tabulated in Table 28-1 be used, particularly in cases of large requirements. To illustrate its use assume a 60 suite garden apartment each with a single bath, with shower and kitchen with dishwashing. Using Table 28-1, the estimated connected load is 60 lavatories X 2 = 120 gallons per hour 60 showers X 30 * 1,800 gallons per hour 60 kitchen sinks X 10 " 600 gallons per hour 60 dish washers X 15 = 900 gallons per hour Total connected demand 3,^20 gallons per hour Not all fixtures will be in use simultaneously. For apartments the use factor is estimated at .3 making the actual hourly demand .3 x 3#420 1,026 gal lons per hour. Warning Obviously, 1,026 gallons per hour averages out to 17*1 gallons per minute. But, do not assume that a tankless heater good for 17*1 gallons per minute would be satisfactory. During the hour instantaneous demands for hot water might be at a rate of several hundred gallons per minute,. Such an amount would be inpractical to supply with a tankless heater unless there was un limited boiler capacity available. The preferred method of handling large hot water demands is with a separate boiler (the IS method) or with tank-type heaters installed in the space heating boiler. In each case a storage tank is used. It is also possible to use the tankless heaters supplied with the A-5 boiler and the two largest sizes of those furnished with the G-Ao as tank type heaters. When this is done a pump must be used to circulate the water through the heater and the tank since the small size of tubing used in these heaters has too much friction to permit adquate wqter circulation by gravity. In Page 28-1 M f1 10774 Table 28-1 Hot Water Demand per Fixtures for Various Types of Buildings GaMonr of water par hour par flxtere, calculated of o final temp*rater* of ,40 F Apartment Houm Ovb Gymnatium Hoipito! Haiti tndurtriat Plant Office Building Private Residence Sdioof YM.CJL 1. Basins, private lavatory... 2. Basins, public lavatory....... 3. Bathtubs................................ 4. Dishwashers*.......................... 5. Foot basins ....................... 6. KitcheD sink............. 7. Laundry, stationary tubs. .. 8. Pantry sink............................. 9. Showers.................................... 10. Slop sink................................ 11. Hydro-therapeutic showers.. 12. Hubbard baths....................... 13. Leg baths................................ 14. Arm baths................................ 15. Sits baths .............................. 16. Continuous-flow baths.......... 17. Circular wash sinks.............. 18. Semi-circular wash sinks.... 19. Demand factor....................... 20. Storage capacity factor11.... 2 4 20 15 3 10 20 5 30 20 0.30 1.25 2 6 20 50-150 3 20 28 10 150 20 0.30 0.90 2 8 30 12 225 0.40 1.00 22 68 20 20 50-150 50-200 33 20 30 28 28 10 10 75 75 20 30 400 600 100 35 30 165 20 20 10 10 0.25 0.25 0.60 0.80 2 12 20-100 12 20 225 20 30 15 0.40 1.00 2 6 20 10 30 20 20 10 0.30 2.00 2 22 15 8 20 30 15 20-100 20-100 3 3 12 10 20 20 20 28 5 10 10 30 225 225 15 20 20 0.30 0.70 30 15 0.40 1.00 0.40 1.00 Diabwaeher requirement* ihoutd be taken from Table 14 or from manufacturer*' data for the model to be uaed, if thi* i known. ___ b Rfttj0 0f storage tank capacity to probable maximum demand per hour. 8tormge capacity may be reduced where an unlimited aupply of ateam ia amilabl* from a central ttreet steam system or large boiler plant. Reprinted by permission from ASHRAE Guide and Data Book - 1962 -i v . C Page 28-2 10775 mak-tng such application the Hydronic Product Group should be consulted. The tankless heater capacities^when U6ed as tank-type heaters, are as follows: Heater No. 530 232 445 Btu/hr. 160,000 249.000 299.000 There are tank-type heaters on the market, produced by heater manufacturers, that will fit American-Standard boilers. IS Domestic Hot Water The IS in the title stands for "indirect steam". In this kind of system a steam boiler is used to heat domestic hot water in much the same way steam is used with a convertor to supply forced, hot water to a heating system. The IS system has a number of advantages over the EW or direct water heating. 1. The hot water has no discoloration. In DW systems the water becomes slightly tinted from its contact with cast iron of the boiler. 2. Scale forming substances which would normally be deposited on the inside boiler surface with EW systems are now deposited on the outside of the steam coil in the external heater. Since these heaters are designed for coil accessibility or removal, they can be readily cleaned when liming becomes excessive. 3. The boiler is working on a closed system with the condensate being returned to it, thereby reducing internal liming to an inconsequential minimum. G-2 boiler prices are quoted only for IS use. However, any steam boiler in the American-Standard line can be used in an IS system. Choice depends on the load required and the fuel desired. Boiler requirements for an IS system are; 1. Standard steam equipment including steam gauge. 2. ASME safety valve. 3. Pressure limit control. 4. Gauge glass with trimmings. 5. Resetting low water cut-off. In addition, the system should be supplied with a CA-666 immersion operating control, installed in the water storage tank at or near the cold water inlet. Page 28-3 10776 Heat i6 transferred to the water through either a coil in the storage tank or an external indirect heater. In both cases, the equipment i6 supplied by other manufacturers who should specify the sizing of the heat exchange equipment. The principle of sizing the boiler in these installations is simple be cause the domestic hot water demand is the only load...and, in addition, the storage tank is located close by the boiler. The boiler's ability to heat domestic hot water is based on its IbB*R gross capacity or its A. G. A. output. Computing the gallons of hot water any boiler can supply is a simple problem of multiplying the gross capacity of the boiler in MBH by a factor dependent on the temperature rise desired. Factors are .... for .... Various Water Temperature Rises 1.2 100F 1.3 90F 1.5 80F 1.7 70F 2.0 60F The equation; Demand (GPH) = MBH x Factor Example; How many gallons of water per hour, at a 100F temperature rise can be supplied by an American-Standard G-25 boiler, which has a gross capacity of 9^,000 Btu/hr. GPH 96 x 1.2.... or 115.2 gallons per hour Similarly ... GPH (at 90F rise) GPH (at 80F rise) GPH (at 70F rise) GPH (at 60F rise) 96 x 1.3 ... or 124.8 GPH 96 x 1.5 ... or 144.0 GPH 96 x 1.7 ... or 163.2 GPH 96 x 2.0 ... or 192.0 GPH For economy reasons, particularly with severe peak demands, it is usual to employ a storage tank in an IS system to permit the heating and storing of water during off-peak periods. Page 28-4 * (I ' 10777 The size of the storage tank and boiler will, of course, depend on the length of peak demand. The equation, with "IT" being number of hours of peak demand Is; N x Demand (GPH) IT x Boiler Capacity (GPH) + .7 x Tank Volume (GPH) OR: Tank Volume (Gals) - N (Demflnd " Boller Capacity) 7 The following tables show various combination of boller capacity and tank volume to meet various demands of both gallonage and temperature rise. Table 28-2 Rat Watar l.p.b. 100 150 200 250 300 550 U oo bSO 500 550 600 650 700 750 800 850 900 750 1000 1050 uoo uSo 1200 1250 1300 MINIMUM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND lOO'V T--per*tTg- P-1a. 0-2 BoLUr-Siaaj 0-40 Bodlar-Slsaa C-60 aoiler-Slxaa 23 2b 25 26 27 28 29 210 211 b03 bob bOS b06 b07 U08 b09' b010 606 687 608 609 60 131 92 50 163 121 80 207 151 no 70 ao 166 b9 223 181 lbl 100 223 120 253 213 171 130 295 192 89 28b 2b3 201 160 366 263 160 58 31b 273 231 blS 303 37b bb6 335 232 129 b06 303 200 98 375 272 169 66 3b3 2b0 137 312 209 106. Tank Tol.(gala,) N(daaand[gph^^>cdl*r caj CO** 0.7 N Numbar of hour* of paak damaw 383 280 177 73 bSS 352 2b9 IbS 77 b23 320 217 149 392 289 220 b63 360 291 93 U32 362 16b b3b 236 506 307 109 379 180 b50 251 S21 323 123 39b 19b b66 265 Page 28-5 I- 10778 Assume gets as the fuel and a demand for 200 GIB. Opposite the 200 GFH demand, under G-2 boiler sizes t&ere are 3 possible combinations to meet these requirements. 1. G-24 boiler and 163 gallon tank (min) 2. G-25 boiler and 121 gallon tank (min) 3. G-26 boiler and 80 gallon tank (min) Naturally, the proposal will suggest the most economical combination. If the peak demand time were doubled to two hours, tank size would have to be doubled. If peak demand went to three hours tank size would have to be tripled. Tank sizes cannot be increased indefinitely. At some point, both economy and necessity will dictate the next larger size boiler. Table 28-3 MINIMUM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND 0OF Temperature Rise Hot Water 0-2 Bcdler-Sliee G-iiO Batler~Siaee G-40 Boiler-Siaea g.p.h. 100 23 21k 25 26 27 28 29 210 211 lk03 IkOlk IkOS U06 lk07 Ik06 U09 U010 606 607 608 609 610 u iso 103 62 200 18U 133 82 30 30 250 256 201k 153 101 50 100 300 2 76 221 173 121 70 172 U3 350 296 21kU 193 1U 90 21k3 111k 100 316 26U 213 161 110 59 311k 136 57 150 336 281 233 182 130 386 257 129 500 356 301k 253 201 32? 200 71 550 600 650 700 750 600 850 900 950 1000 1050 1100 uso 1200 1250 1300 375 321k 273 U00 272 lie 396 3iklk 313 2Uk 86 US US 286 157 Tank Tol.fgaJj.)" N(denAndEph^-boller cap.g >h])l 0.7 357 229 100 N * Nuaber of hours of peak demand U29 300 172 372 2U3 Hi Uklk 311k 186 57 386 257 129 U57 329 200 111k . U00 272 186 671 3U3 257 US 329 80 U86 IkOO 152 Ik71 223 291k 366 117 '! 1 f 1 ' Page 28-6 10779 Here a demand for 700 gallons an hour with an 80F temperature rise dictates either; 1. g-406 boiler with 357 gallon tank 2. G-407 boiler with 229 gallon tank 3. G-408 boiler with 100 gallon tank Again, one will cost less...and, again tank sizes will have to be doubled, if peak demand stretches out to two hours. The following table covers the same three boilers with a 60F temperature rise, and still smaller tank requirements. Table 28-4 MINE4UM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND hot Water Desand 100 150 200 250 300 350 loo 650 500 550 600 650 700 750 eoo 650 900 950 1000 1050 uoo 1150 1200 1250 1300 60f Ts-rp^rmt^rfl Riga 0-2 ^oiler-Siiea G-liQ Boller-Sltee G--60 3oller-5i*ea 23 26 25 26 27 2& 29 210 211 U03 iiOU li05 U06 1*07 aoe L09 uio 606 77 1U9 30 220 152 83 223 155 86 66 295 226 157 87 157 366 297 229 160 91 229 57 369 300 232 163 96 300 129 660 372 303 236 166 98 yn 200 512 663 375 306 237 169 100 663 2 72 100 666 377 309 260 172 SIS 363 171 669 380 312 263 615 263 72 652 383 315 586 316 163 655 386 386 216 657 657 286 115 529 357 186 629 257 86 500 329 157 600 229 57 Tank to1*(gala.J-N^daaaad^phj-bailer c*p.(jC N Number of houre of peek demand 0.7 U72 300 12?566 372 200 663 272 100 515 363 171 57 615 263 129 586 3a 200 Page 28-7 V 1 ('1 10780 The following three tables provide the same kind of information on Ar coliner, A-5 and. A-7 boilers. Table 28-$ MINIMUM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND 100F Tesipereture Rise Hot Water Dea*ad g.p.h. 100 Arcollnar -Sites A*5 Boiler-Sitas A-7 Boiler-Sites 153 15U 155 356 506 505 506 S07 508 509 510 511 70S 706 150 1*9 200 120 60 250 191 131 76 300 263 203 Hi? 106 550 336 271* 219 177 53 uOO 606 366 290 267 126 U50 617 362 320 196 50 500 633 392 268 121 550 663 339 193 56 600 610 266 127 650 682 336 159 57 700 U07 270 129 750 679 362 2 00 63 BOO 613 272 136 S50 685 363 206 69 ?00 635 278 160 Tank Tol.tgele.J^'fdenendQphJ-boller cep.gph])f 0.7 950 686 369 231 76 N Number of hours of peak demani 1000 620 283 ,166 1050 UOO 1150 1200 1250 1300 692 356 217 77 626 289 169 87 697 360 220 158 632 292 230 503 363 302 635 373 123 Page 28-8 V ' c' 10781 Table 28-6 MINIMUM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND Hot Water Deaud f.p.h. 100 6Qy Towperatqre Rle Arcoliner-Slie* A-5 Ballar -51*e 153 151* 155 156 sol* 505 506 507 508 509 510 511 150 200 ?5o 300 350 LOO LSO 500 550 600 650 700 750 800 850 900 950 1000 1050 noo 1150 1200 1250 UOO 80 166 51 223 123 31 295 191* 103 366 266 171* 106 1*37 337 21*6 177 1*09 318 21*9 1*30 389 320 111 1*60 352 183 1*63 255 3 326 155 397 226 1*69 297 69 369 11*0 1*1*0 211 512 283 351* U9 1*26 120 1*97 191 263 331* 106 1*06 177 Tank Tol.fgala.)^(danand^iphj^>clXer cap-^iph^-iO.? N Ntaber of boon of peak a*--** Page 28-9 "t - 10782 Table 26-7 MINIMUM STORAGE TANK CAPACITIES 1 HOUR PEAK DEMAND jlroolliMr Slsaa lot Vatar g.p.h. 153 15h 155 156 IX $4i* 60F 1-5 Bailor Slsaa 505 506 507 506 509 510 R1m sn ISO 200 79 250 150 71i 300 222 11*6 77 350 uOO k50 500 550 600 650 700 750 800 650 900 950 IOOO 291* 217 11*9 97 365 239 220 169 u36 360 292 2!*0 83 507 1*32 363 312 155 503 1*35 383 226 UU 506 1*55 297 116 526 369 187 1*1*0 259 87 512 330 160 1*01 232 51* 1*73 303 126 51*5 375 197 1*1*6 269 97 516 31*0 169 Tack Toi.(gitla.)* R^da4adCiphJ-bcdlr cap.|[fphjj^07 N Nuabar of hours of paaJc daaaad 1050 1*12 21*0 69 nx 1*83 312 11*0 11S0 555 383 211 1200 1*55 283 111 1250 526 351* 183 1300 1*26 251* 79 V 1 f, Page 28-10 10783 GREENHOUSE HEATING CHAPTER 29 GREENHOUSE HEATING Greenhouse heating is, of course, different from space heating for human comfort. Temperature is frequently maintained at less than 70F, which increases the emission rate of radiation. Studies of greenhouse heat loss indicate that the glass area is a good base for calculating the load. The necessary allowances for wall loss and small amounts of infiltration have been made in the tables that make up the body of this chapter. These Babies, 29-1 through 29~7, have been prepared for 1,000 square feet of glass...they cover an outdoor temperature range of 20F down to -30F and an indoor range from U0 to 70F. They are based on data compiled by the United States Department of Agriculture and published by the"Heating and Ventilating Magazine" Knowing the number of thousands of square feet of glass in a greenhouse, the following information can be obtained; 1. The total Btu per hour heat loss for sizing the boiler or boilers. 2. The square feet of radiation required for a. Steam at 220F. b. Gravity circulated hot water at l60F. c. Forced circulated hot water at 210F. 3- Linear feet of pipe radiation required for a. Steam at 220F b. Gravity circulated hot water at l60F c. Forced circulated hot water at 210F As the tables themselves indicate, only two additional pieces of in formation are necessary; 1. The indoor design temperature 2. The outdoor design temperature A6 a general rule the greenhouse owner will know what maximum inside temperature he requires for his crops. If there is any question Table 29-9 provides a list of vegetable and flower crops and their customary tempera ture requirements. The outside temperature i6 the outdoor design temperature for heating that is in common use in the area. Let's see how they work. Page 29-1 I l f( I 10785 The problem: A greenhouse is being built for general purpose use. Its glass area i6 9>500 square feet...the outdoor design temperature is -10F, the indoor design temperature 55F- The builder plans a forced hot water system and you have sold him on using cast iron radiation. Inside design temperature of 55F is covered in Table 29-4. Then under the -10F outside temperature heading, you will find on the last line "Forced hot water 210F" that 326 square feet of EDR is needed for each 1,000 square feet of glass area. 9,500 square feet of glass, then, will require 9*5 x 326 or 3>097 square feet of EDR. On the top line, you will note the heat loss of 85,300 Btu/hr. per 1,000 square feet of glass. "his greenhouse will need a boiler with a capacity of 9*5 x 85,300 or <c 53,350 Btu/hr. of net installed radiation. To size supply and return mains for steam systems, use the standard pipe sizing tables given in Chapter 15. The figures should be used in conjunction with the Btu/hr. load equated to EDR by dividing by 240. To size supply and return mains for forced hot water heating, use the standard milinch method discussed in Chapter 20. For supply and return main sizing on hot water gravity systems, use Table 29-8 on Page 29-10. Page 29-2 10786 1r Inside Temperature 40F Table 29-1 REQUIREMENTS FOR EACH 1,000 SQUARE FEET OF GLASS OutBide Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 28,600 41,000 53,800 66,800 79,200 92,200 Linear Feet of 1-1/4" Pipe Steam 132 190 250 305 366 425 Linear Feet of 2" Pipe Gravity Hot Water 189 271 358 443 525 610 Linear Feet of 3-1/2" Pipe Gravity Hot Water 116 167 220 272 323 374 Linear Feet of 2" Pipe Forced Hot Water 120 173 226 280 333 388 Ca6t Iron Radiation Square Feet Steam 88 126 165 204 242 283 Hot Water Gravity Hot Water Forced 154 220 289 360 426 495 97 139 162 225 268 312 Page 29-3 M ,.f,i 10787 Inside Temperature k?F Table 29-2 REQUIREMENTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 34,800 47,500 60,100 72,600 85,300 98,000 Linear Feet of 1$" Pipe Steam - 220F 168 230 292 352 4i4 475 Linear Feet of 2" Pipe Gravity Hot Water - l60 242 330 419 505 591 680 Linear Feet of 3^" RLpe Gravity Hot Water - l60F 150 205 258 313 366 422 Linear Feet of 2" Pipe Forced Hot Water - 210F 153 209 264 320 374 429 Cast Iron Radiation Square Feet Steam - 220F 111 152 192 232 272 313 Gravity Hot Water - l60F 198 270 342 413 485 555 Forced Hot Water - 210F 122 166 211 254 299 343 i t, i Page 29-4 10788 Inside Temperature 50P Table 29-3 REQUIREMENTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 41,200 53,800 66,450 79,000 91,700 104,500 Linear Feet of l" Pipe Steam - 220F 207 270 333 397 460 -rf- C*V/J\ Linear Feet of 2" Pipe Gravity Hot Water - l60F 304 397 490 582 676 770 Linear Feet of 3i" Pipe Gravity Hot Water - l60F Linear Feet of 2" Pipe Forced Hot Water - 210F 188 245 302 360 419 475 189 247 305 362 420 478 Cast Iron Radiation Square Feet Steam - 220F 140 182 224 267 310 353 Gravity Hot Water - l60F 248 324 398 474 550 626 Forced Hot Water - 210F 150 196 242 286 234 380 i * i f, i fte 29-5 10789 Inside Temperature 55F Table 29-4 REQUIREMENTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 47,500 60,500 72,800 85,300 98,500 111,000 Linear1 Feet of l" Pipe Steam - 220F Linear Feet of 2" Pipe Gravity Hot Water - l60F 245 315 377 440 508 571 368 472 568 663 763 862 Linear Feet of 3^" Pipe Gravity Hot Water - l60F 231 296 356 415 481 541 Linear Feet of 2" Pipe Forced Hot Water - 210F 228 292 350 409 472 532 Cast Iron Radiation Square Feet Steam - 220F 166 212 255 299 345 398 Gravity Hot Water - l60F 300 382 460 540 623 702 Forced Hot Water - 210F 182 221 278 326 376 424 Page 29-6 f, 1 10790 Inside Temperature 60F Table 29-5 R35UTREM2TTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 53,700 66,600 79,100 91,700 104,500 117,30 Linear Feet of l" Pipe Steam - 220F 289 358 426 493 562 629 Lineair Feet of 2" Pipe Gravity Hot Water - l60F Linear Feet of 3?" Pipe Gravity Hot Water - l60F Linear Feet of 2" Pipe Forced Hot Water - 210F Ca6t Iron Radiation Square Feet Steam - 220F Gravity Hot Water - l60F Forced Hot Water - 210F 446 278 270 196 360 215 549 342 336 243 447 267 654 408 397 289 531 315 768 862 971 472 541 606 46l 524 588 334 381 427 615 700 788 367 4l8 469 Page 29-7 ' I'1 10791 Inside Temperature 65F Table 29-6 RBQUIRaffiHTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature 20 10 0 -10 -20 Heat Loss Btu/hr. 59,700 72,600 86,400 98,300 111,000 -30 123,000 Linear Feet of l" Pipe Steam - 220F 336 403 479 550 621 690 Linear Feet of 2" Pipe Gravity Hot Water - l60F Linear Feet of 3i" Pipe Gravity Hot Water - l60F 529 641 752 870 980 1,087 333 403 476 549 617 685 Linear Feet of 2" Pipe Forced Hot Water - 210F 313 379 446 513 578 645 Cast Iron Radiation Square Feet Steam - 220F 228 277 326 375 424 Gravity Hot Water - l60F 427 519 610 702 792 Forced Hot Water - 210F 250 304 357 4ll 464 470 877 515 Page 29-8 ' 10792 Inside Temperature 70F Table 29-7 REQUIREMENTS FOR EACH 1,000 SQUARE FEET OF GLASS Outside Temperature Heat Loss Btu/hr. 20 10 0 -10 -20 -30 66,250 79,200 91,700 104,800 117,500 129,500 Linear Feet of l" Pipe Steam - 220F 394 470 546 621 700 770 Linear Feet of 2" Pipe Gravity Hot Water - l60F 613 735 855 971 1,099 1,205 Linear Feet of 3?" Pipe Gravity Hot Water - l60F 391 467 543 617 Linear Feet of 2" Pipe Forced Hot Water - 210F 361 431 503 571 Cast Iron Radiation Square Feet Steam - 220F 265 317 367 419 Gravity Hot Water - l60F 505 605 700 798 Forced Hot Water - 210 F 289 346 400 457 694 645 470 896 513 763 709 518 988 565 Page 29-9 10793 Table 29-8 Size cf Mains for Gravity Hot Wnter Pipe Coils (Based on l60F water, and a total length of supply and return mains of not over 200 feet) > 6 . .y Page 29_10 10794 Table 29-9 Customary Temperatures for Greenhouses Type of Plant Carnation Conservatory (general collection, winter, garden, etc.) Cool Cucumber Fern Forcing General Purpose Lettuce Orchid, warm Orchid, cool Palm, warm Palm, cool Propagating Rose Sweet Pea Tomato Tropical Violet v n0 1 vn V/l Temperature Range Degrees F 45 - 55 60 - 65 45 - 50 65 - 70 60 - 65 60 - 65 55 - 60 1+0 - 45 65 - 70 50 - 55 60 - 65 55 - 60 55 - 60 45 - 50 6 5 - 70 65 - 70 40 - 45 '! ' [' I Page 29-1.1 10795 CHAPTER 30 HEATING SWIMMING POOLS 10796 CHAPTER 30 HEATING SWIMMING POOLS There are two common methods fcir establishing the heat loss of the water in a swimming pool. They are based on; 1. The volume of water 2. The surface area of the water The volume method considers only the heat necessary to raise the water volume a certain number of degrees fahrenheit in an hour. Arbitrarily, the industry has a set standard for sizing boilers to heat swimming pools on the basis of raising the water temperature by 20 in a 40 hour period in the South and with indoor pools...in a 30 hour period across the middle part of the country and in 20 hours in the North. These factors can be converted to degrees of water temperature rise per hour i 1. l/2F per hour in the South and in indoor pools 2. 3AF per hour across the middle part of the country o 3- IF per hour in the northern part of the country These are arbitrary and there may be minor differences in any one locality, depending on altitude and humidity. However, since the quantity of heat estimated at these levels is greater than the heat loss, once the pool is up to temperature this procedure has been found to meet the requirements. The equation is: Btu/hr ' Input - L x W x D x _B_o_il--er Effic. ie--n--c---y- x T Where L Length of the pool -- feet W - Width -- feet D " Average Depth -- feet 62 Veight in pounds of 1 cu. ft. of water T Degrees of Temperature rise per hour Actually, of course, any similar equation involving any substance other than water would al6o include the factor of the specific heat of the substance. Since the specific heat of water is "1", and anything multiplied by "1" is unchanged, it is not necessary to U6e the factor in this kind of equation when water is the substance. Page 30-1 v . f, 10797 Example: In Connecticut, what 6ize gas-fired, boiler, operating at 80$ efficiency, is needed to heat a pool 30 feet long, 16 feet wide, with an average depth of 5 feet? Our equation now is; Btu/hr. Input 30 x 16 x 5 x x 1 186,000 .8 A boiler with at least a 186,000 Btu/hr. input is required. If, however, the boiler were rated at 70$ efficiency, the equation for the same .pool would bet Btu/hr. Input - 30 x 15 x 5 x ^ x 1 - 212,570 7 If the pool in question were the same dimensions but In a gymnasium in a school in Connecticut or outdoors in Georgia, the equation for the same boiler, at 70$ efficiency would be; Btu/hr. Input 30 x l6 x 5 x -- x l/2 106,290 7 The area method of "sizing the boiler" is based entirely on the cooling action of both the wind and surface evaporation. Depth of the pool, there fore, is not a factor. Experience indicates that the pool will lose 12 Btu per hour per square foot of surface area for every degree of temperature difference between the water and the surrounding air temperature. The area method equation is: Btu/hr. Input LxWx 12 Boiler Efficiency (Tv - Ta) Where L = Length W - Width Tw Temperature of Water in F Ta Average air temperature in F Example; Assume the 6ame pool, outdoors in Connecticut. The owner wants to use the pool between September 15th and October 15th. During thi6 period the average air temperature get to 55F. He wants to keep the pool water at 80F. Again, a gas boiler with 80$ efficiency has been decided on. "i ' c ' Page 30-2 10798 The equation: Btu/hr. Input - 30 x 16 x ^ x (80-55) .8 or-' .30. x_l6 x 12 x 25 . l80j000 With a boiler rated at 70$ efficiency we would have; * . 205,700 Again, let's move the same pool with a gas boiler operating at 70$ efficiency, indoors. Assume the gym is kept in use from 8;00 a.m. to 10;00 p.m. with a space temperature of 70. After 10;00 p.m., it is allowed, on the thermostat's night setting, to cool to 60 , with the morning cycle set for 7:00 a.m. Average temperature under these conditions would be 66. Then; Btu/hr. Input 30 x 16 x ^ x (80-66) I or: 30.x 16 x 12 x Ik m 1oQ)33Q Thus, the two methods of calculating the boiler capacity In Btu/hr. for three different situations involving the same pool size are; Outdoors, Connecticut, 80$ efficiency Volume 186,000 Area 180,000 " " 70$ Indoors, " 70$ " 212,570 106,290 205,700 108,350 * ' >i' Page 30-3 10799 CHAPTER 31 MAINTENANCE 10800 CHAPTER 31 MAINTENANCE Regular, methodical maintenance of any heating system pays off in longer life and more economical operation. Burners -- oil, gas and stokers -- should be checked, cleaned and ad justed according to manufacturer's recommendatiors at least once a year. Controls, too, need an annual inspection. Changes in calibration can be detected and corrected. All electrical contacts should be checked and cleaned. Minor pitting can be cured by smoothing...severe pitting only by replacement. New boilers, either hot water or steam whether in new systems or re placements in old systems, require daily inspection for the first several weeks of operation. Water should be drained from the boiler at each inspection. If the water is muddy, draining should continue until it runs clear. Draihing should be accomplished with the water hot and burner off. With dry base boilers more than one drain may be desirable. The most common problem with new steam boilers is "foaming". In new steam systems, the condition is aggravated by oil in the piping, left over from the pipe threading operation, which floats back to the boiler with the condensate. Almost every time a new 6team boiler is put into operation oil and sand will be found floating on the water in the boiler, particularly when the boiler is part of an entirely new system. The strength of the film of oil...surface tension...is much greater than that of water. Instead of the bubble of steam breaking easLly through the surface of clear water, it now blows a soap-like bubble. These bubbles form a froth which blankets the entire surface of the water, which holds back the pressure being built up in the hot water until it becomes strong enough to lift large portions of the blanket and blow it out of the boiler. Often some of the boiler water is lifted with the foam and carried along into the system. This action is called "priming" and results in a rapid lowering of the water level and burner shut-down by the low-water cut-off. With oil burning boilers, too frequent action by the low-water cut-off has a secondary effect on the stack switch. Rapid cycling causes the stack switch to go to safety position, pre venting the burner from re-starting. An inexperienced service man might replace the stack switch which is operating perfectly and miss the real reason for its action. Page 31-1 * i t1' 10801 In addition to frequent action by the low-water cut-off, there are a number of other "indicators" of foaming. 1. Because of the blanket of foam the boiler does not generate enough 6team to fill the radiation. 2. Because of the periodic priming action, water in the gage glass, following the water in the boiler, surges up and down, violently, in wide swings. 3. When the safety valve is opened both water and steam will blow out instead of steam alone. 4. A small amount of boiler water drained into a sauce pan and put on a hot plate will foam up and boil over. To eliminate foaming, it is common practice with large steam boilers to drain condensate into a sewer for the first couple of weeks of operation. Periodic "saucepan" tests of the condensate will tell when it Is clear of oil and sand and safe to return to the boiler. The smaller water content of gas boilers, of course, aggravates the foaming problem. Once a boiler foams and primes, it should be cleaned by the blow-off method. The chemical treatment is easy but never sure. The blow-off method is sure but it may have to be done several times... weekly for about three weeks. American-Standard oil and coal-fired steam boilers are provided with blow-off tappings. To give a G-60 boiler a surface blow-off the safety-valve tapping may be used. On the G-40 use tapping B. See Technical Catalog Bulletin for G-40. Remove the safety valve or plug as the case may be and install a nipple, a gate valve and some drain piping. The water level is raised to the blow off tapping and the boiler fired until steam pressure is developed. The gate valve is then opened and the outrush of steam sweeps the foam off the top of the water and into a drain. After the pressure has dropped, water is fed into the boiler slowly and the burner kept operating. Any dirt and oil is floated out the blowoff. This process may have to continue for a considerable period depending on the water conditions. The blow-off is now closed and 6team pressure allowed to build up to 10 psig. The gate valve is opened once more to blow-off any additional foam that may have formed. Page 31-2 10802 The burners are 6hut off and the boiler drained. After refilling the boiler, start the burner and raise the steam pressure to 10 psig. Open boiler drain to flush any dirty water out of the boiler water legs. In dry base boilers a drain valve should be installed in each leg or on the return manifold. The water must not be allowed to rise above the blow-off valve as it would trap the dirt and grease above the valve allowing clean water to drain off. A boiler cannot be cleaned of grease and oil if it is not hot. Merely draining the boiler to clean it will result in surface grease and dirt clinging to its sides, and rising to the surface when the boiler is re filled. In hot water systems, excess dirt and oil sometimes cause the liberation of substantial amounts of marsh gas which slows water circulation. This situation can usually be handled by a chemical cleaner in accordance with in structions of the cleaner manufacturer. Boilers not in Operation In winter, the boiler, returns and system -- if hot water -- should be completely drained. Flues should be cleaned and all access doors left open. In summer, the boiler flues, especially on coal and oil fired boilers, must be completely cleaned. Gas fired boiler flues stay clean when burners sure in proper adjustment suid ample air is available for combustion. Leave all access doors open. Leave water in a hot water boiler and system during summer months. Fill the steam boiler completely with water during the summer. This stops internal corrosion at the water line during shut down. Be sure to drain excess water out before firing the boiler in the fall. Page 31-3 10803 CHAPTER 32 COMPETITIVE COMPARISONS CHAPTER 32 COMPETITIVE COMPARISONS Competitive comparisons, vhile not often made specific, are one of the salesman's strongest assets...if he knows them. This chapter provides these comparisons...as of the date noted on each chart. Products will change and as they are changed, it is important that you revise these charts 60 that you are always ready to; 1. Stress your product's advantages. 2. Be aware of competitive claims and have the best answers to them. Since convenience and cost of assembly are important in any sale, we note several basic assembly factors. 1. Wet base boilers are easier to assemble than dry base boilers because each section has its own base (American-Standard A-5) N. B. However certain American-Standard dry base boilers (A-7 and G-60) are furnished with bases to facilitate assembly. 2. American-Standard boiler sections pull tightly together, elimi nating the need of asbestos wicking between sections. 3. Smaller sections are more easily handled and assembled than large double sections. V M1 Page 32-1 10805 Table 32-1 COMPARATIVE DATA. ON (W*0 GAS-FIRED BOILERS Competitive Features AR & SS National Peerleea Burnham Weil^tcLain Bryant Bryant H. B. Smith G-kO U.S. 16C Series 50 Holiday 70 Type H 222 (W) 223 (S) Century 11 Common section for or less tankless Yes No No No No No No No Common tank less heater with steam & vater. Tes Yes Available in sections factory assembled. Yes (up to G-u06) Only 3 & li sect. No No Yes Yes No No No No Yes Yes Yes No Available for dual fuel. Yes Yes No No Non-protrud ing draft hood Yes No No No No No Yes Yes No No No No Optional jacket ex tension cover ing left hand end section. Yes Yes No No No No Yes Yes Available for 50 lbs. PSI Yes No Yes No Yes No No No Integral air eliminator Yes No No No No No No No Deluxe jacket standard Yes No Yes No separate base required Yes No No Internal water heater-capacit .es botl steam. L vater | 3-9gprn 1 both 32-6gpm -- Yes Yes No No Yes No 3-3A-15gpm for water. 3-7-l/2gpm for steam. 3-10 1/2 gpm No No No Yes f V- both -- 2.2 - StD gpm '1 * . r, > 10806 Table 32-3 A-5 Feature Comparisons Features AR & SS Burnham National H. B. Smith Weil-McLain __ _____________ "A-5" "PaceKlng" "2$B" "27-37 Series" 200 &250A-72 & A-82 Water Line li6 l/l" Wet Base construction Yes 52 1/2" No 45" 45 lA" to 51" 47 3/8" to 57" 47 lA" to 55" Ye8 No No No /' Section Assembly Jacket Extension A-5 util izes one set of tie rods 4 bot tom slip nipples Available Same Not avail. Same Avail. Same Not Avail. Require short individual tie rods Not Avail. Requires short individual tie rods, asbestos rope needed to prevent air leakage. ' Jacket extension avail on A-72 only. Boiler- Burner Unit Yes No No No No Ye 3 Common in ternal tank less heater Yes with mani fold arrange ment No No No Provisions for singl or double domestic No water heaters - A-82 only. Water work ing pressure 50 lbs., re g. 30 lbs. 30 lbs. 30 lbs. Number & Tapping sizes a) supply b) return 2-4" 4-2 1/2" 4-4" 2-4" "27" "37" 2-3" 3-3" 2-3" 2-3" 2-4" 4-4" 40 lbs. 2-3" 2-3" 30 lbs. ny2" "82" 2-3" 2-3" 2-5" 2-4" Internal Water Heater 4-l6gpm Capacities (both) water 4l-l5gpm steam 3i-9|gpm *27" 27 3|-6gpm 3-7 gpm (both) (both) "200" water 4-8gpm steam 4-6gpm "250" water 4-12gpm steam 4-6gpm 72" 4i-6gpm (both) 82M 7 -9gpm . (dual 16-lf Page 32-4 1 10807 Table 32-2 0-60 Feature Comparison AR A SS National-U.8. Features0-60________________ "66 Seriea" Deluxe Jacket Standard Tea Yes Peerleeo "150 Series" No Weil-McLain Bryant Type J________ Model 630 Yes No Water Work ing Pressure 501ba. reg. 301bs. reg. 801be, opt. 501bs. opt. N.C added charge 301ba. reg. 801bs, opt. Added charge 301ba. reg, 301ba. reg. 75lba. opt. N.C. no options Height 66 1/8" 69 l/lt" 55 1/2" 65 3A" 67 1/2" Water Line Lit" lt5" hi 1/2" US 3A" ItIt" Boiler Base Cast Iron Steel Cast Iron Steel fraaed Steel Section Avaliability 6 to ltl It to 23 5 to 37 5 to 37 10 to 36 Flue Connection Assembly Boiler No. A aite of tappings a) flew b) return 12" - 30" all lit" except 10" - 30* Model 5(12") G-60 utilisee one set of ti s 2ec^?Pcons. rods & top A bottom nipple 8 on both ends Of section 2-nipple sect. cons. 5-6" 5-6* 2-6" 2-6" 2-6" 2-6" Available for Dual Fuel Tea Tea lb 10", 12", A" only all lit" excluding Model 10 (12") requires short individual tie rods, 2 nipple sect. cons. 2-nlpple sect. cons. 5-6" 2-It"--3-3" 2-6" 2-6" Tea No "! ^ * f11 Page 32-3 10808 Table 32-^ A-7 Feature Compartson Feature AR k SS "A-7" National-0,5, "47 Series" Weil-McLain "HO-liO" Domestic Water Heater Arrange ment. Furnished with ex ternal heater tap ping. May be equipped with an integral type tankless heater or a storage tank heater. Not available H, B. Smith 340 and 440 Available with mani fold heater on spocial order. Water Working Freesure. 50 lba. regularno options. 30 lbs. regular. 40 lbs, regular 30 lbs.regular- 80 lbs. option 50 lbs.option N.C. Added Charge. Jacket Aralla bility. Available with sturdy 20-gauge steel Jacket. Available with Jacket, Available with Jacket. No Jacket available. Aseenbly Boiler. A-7 utilises one set of tie rods k top k bottom slip nipples. Same as "A-5". Requires short individual tie rods, multiplicity of parts in ex cess of slip nipples. Requires special tools k special uppar and lesrer manifold connections for all sections. Dry or Wet Top Nipple. Top nipple part for steam partial ly submerged in water Boiler rear section tapped for Wet top nipple - external water moderate tapping heater, eliminating and manifolding header connections of sections. from sections for external heater. 3" tappings furnish ad regularly for this purpose. Dry top nipple requiring ex pensive heater manifold U spec ial tappings. Dry top nipple re quired special mani fold & heaters. Height 70 7/8* 69 3/8* 79 lA" 78" and 76" Width li9 3AM 49 1/2* 50" 51" and 64" Length 41 1/2" - 94" 42 1A" - 105 lA" 42 3A" - H4 3A" 49" - -- 85" Page 32-5 i t (i i 10809 Features Water Line. Flue Connect ion. Steel Pedestal Base Option, Boiler-Burner Unit Tapping Sites a) Flow b) Return. Table 32-1 (Coat'd.) AR & SS "A-7" 59 1/2" A-7 Feature Comparison National-O.S. . Ii7 Series" 59 1/2" We ij.-Me Lain "HO-tO" 67" 16" 16" 18" Yea Yea Yea Yes Yea Yes 5-1" 2-6" 2-6" 1-1" 1-5" 2-5" H. B, Smith 310 and UlO 56" to 61 1/2" 18" tc 20" Yea Yea "310" TV 2-1" "Ho" TV 2-5" u1 Page 32-6 10810 GETTING THE ORDER CHAPTER 33 CHAPTER 33 GETTING THE ORDER Which, of course, is the sole reason for preparing, writing, printing... AND READING...this book. Product knowledge is a salesman's byword...the basis for his most potent selling arguments. The more technical, the more flexible, the more varied, the more it resembles a complex system than a single component, the more important... and potent...knowledge of the product becomes. This book will not give you all the answers. No single book can. Dozens of sources were used to gather this material. It was designed to give you a basic understanding of the problems...a method for solving them...and an appreciation of the extent of product knowledge necessary. The final step in any large heating system sale will often be the formal submission of a proposal with specifications. This is, of course, a very important step in getting the order and this chapter contains some sample proposals to act as a guide. Even more important are the inspections, conferences and conversations that precede proposal preparation, and in many cases...particularly in the replacement market...are the only steps to the sale. Here it is that product and system knowledge pays off. Do you understand the problems? Can you help solve them? Can you suggest better values... either by improving the quality of the system or by finding a lower cost way of accomplishing part or all of the Job? The more money a man spends for a product...the more he wants to be sure that it, the company behind it, and the salesman in front of it are right. And a large heating system represents a lot of money. Product and installation costs are high, but they're only a fraction of the money he'll be spending on it for the next 20 or 30 years -- or longer. And so, differences in price in competitive proposals -- occasionally even reasonably large differences -- are sometimes less important than the quality of the salesman's product knowledge. The important thing he needs is reassurance that your system, your product, will do the Job, without overdoing it. An undersized system will create serious trouble for him -- and you -- and American-Standard. Page 33-1 V r1 * 10812 An oversized system will take money ont of his pocket, and in the long run, out of yours -- and American-Standard* In the early stages, off-the-cuff estimates on costs, Btu/hr. can cover a reasonably wide range. Sizing a pipe, a pump, a boiler or an expansion tank cannot cover any range at all. Be precise. Make your answers to his questions precise. And make them only when you are absolutely, one hundred percent guaranteed sure. If you're almost absolutely, ninety-nine and forty-four one-hundredths ercent, warranteed sure...don't answer. Tell him you don't know the answer ut that you'll get it for him, fast. Then get it for him...fasti When you've got all the facts and figures, use the following samples as a guide and make up your proposal. o' 'rJ V r* Page 33-2 10813 Sample Specification for Gas Fired Boilers Contractor shall install vhere indicated on plansg&s fired gefm boiler(s) having a net I"B*R rating offor automatic operation on gas. Boiler{s) shall be constructed in accordance with ASMS Code for Low Pressure Heating Boilers, and bear its symbol. Section IV. Boiler(s) shall be A. G. A. approved for a maximum input ofBTU per hour. Boiler(s) shall be constructed of cast iron sections with Vertical flues with one at mospheric drill port or removable ribbon burner per flue way. Manufacturer shall supply each boiler with main automatic gas valve, safety pilot with thermocouple as required by A. G. A., Gas pressure regulator (except for LP), high limit control, water or steam boiler trim as required by ASME, integral canopy and drafthood. (For G-2 and G-40 boilers an air eliminator as an integral part of the boiler and tankless coil of GPM capacity) Additional equipment required as follows; (Select one of the following specific equipment desired) Manufacturer will furnish, in addition to the above, basic additional controls necessary to meet F. M. & F. I. A. requirements including electronic controls to provide electronic supervision and' all primary gas pilots and electric ignition on all pilots and 100 per cent safety shutoff. Boiler(s) shall, after equipment is properly installed by contractor, be fully auto matic in operation with intermittent pilot ignition on all pilots. or Manufacturer will furnish boiler, in addition to the above electronic controls, to provide the following: (select one of the following) 1. Manual ignition non 100 per cent shutoff continuous pilot 2. Manual ignition 100 per cent shutoff continuous pilot 3- 100 per cent 6hutoff with electric ignition on primary boiler pilot providing equipment component check of each boiler cycle. Manufacturer will furni6h factory wired and assembled electronic control panel suitable for wall hanging with main power on and off switch, pilot and gas valve switch, indicator lights for power,on, pilot off, gas valve on. Boiler shall be as manufactured by American-Badlator & Standard Sanitary Corporation, New York, New York, Model No. or approved equal. . r, Page 33-? 10314 Sample Specification for Oil Fired. Boilers Contractor shall Install where indicated on plansoil fired steam or water boiler(s) having a net I*BR rating ofat a firing rate of gph. Boiler(s) shall be constructed in accordance with ASME Code for Low Pressure Heating Boilers, Section IV. Boiler(s) shall have a gross IB"R output ofBTU/hr. Manufacturer shall furnish each boiler with steam or water trim in ac cordance with ASME requirements, with UL approved oil burner designed and tested for boiler described above. Controls shall include high limit con trol, primary control, fuel pump, draft stabilizer. Where required, manu facturer will furnish special pedestal base to raise boiler to correct height to provide-proper combustion area required by burner. Additional equipment required for firing rate of 7 gph or more.(Select one of following specific equipment desired) Boiler manufacturer will furnish oil burner equipped with flame safe guard equipment with basic controls to meet F. M. and F. I. A. approval with control panel to provide 15 second trial for Ignition and 2 to 4 second flams failure shutdown. Photocell mounted in burner. Oil valve, motor transformer and Photocell to be factory wired. or Boiler manufacturer will furnish oil burner equipped with flame safe guard equipment as required by UL to provide 15 second trial for ignition and 15 second flame failure shutdown. Photocell mounted in burner. Oil valve, motor, transformer and Photocell to be factory wired. Boiler & Burner shall be as manufactured and equipped by American Radiator & Standard Sanitary Corporation, New York, New York, Model No. _______or approved equal. ' [i Page 33-^ 10815