Document VGy2Gx8JMdZ2r7794Gb4X8Y4p

v 45-'; yry... American Society of Heating and Ventilating Engineers Guide, 193^' boilers. Good connections made to a good chimney will usually res. > a rapid response by the boilers to demands for heat. 1 PIPE CONNECTIONS TO BOILERS The pipe connections which must be made to both steam boilers hot-water heaters are: 1. Steam or flow connections from the top. 2. Return connections to the bottom. 3. Blow-off or drain connections. 4. Cold water connections for filling. The steam or flow connections and also the return connections must carefully designed to provide for expansion of the piping, as well as proper size and number so as to give low outlet velocities, and unifor^ distribution of the return water over the boiler heating surfaces. T velocity of flow through the outlets of low pressure steam heating boilers should not exceed 15 ft. per second if entrainment of moisture is to be prevented, as with higher velocity the steam leaving the boiler may carry; water with it. Blow-off or drain connections should be made near the boiler and so; arranged that the entire system may be drained of water by opening the' drain cock. In the case of two or more boilers separate blow-off connect tions must be provided for each boiler on the boiler side of the stop valve on the main return connection. Water service connections must be provided for both steam and water boilers, for refilling and for the addition of make up water to boilers, This connection is usually of galvanized iron pipe, and is made to, the return main near the boiler or boilers. The heating contractor is required to niri this line to the nearest water service main, in which the plumber has left a plugged tee. For further data on pipe connections for steam and hot-water heating systems, see ChaptersTO and 11. BOILER TROUBLES A complaint regarding boiler operation generally will be found to be due to one of the following: , 1. The boiler fails to deliver enough heat. The cause of this con tiou may be: (0) poor draft; (b) poor fuel; (c) inferior attention or firing; (d) boiler too small; (e) improper piping; (/) improper arrangement of sections; (g) heating surfaces may be covered with soot and (h) insufficient radiation installed. 2. The water line is unsteady^ The cause of this condition may bef1 (a) grease and dirt in boiler; (6) water column connected to a very active section and, therefore, may not be showing actual water level in boiler, (e) boiler operating at excessive output. 3. Water disappears from gage glass. This may be caused by: (a) priming due to grease and dirt in boiler; (b) too great pressure difference between supply and return piping causing water to back into return; (c) valve closed in return line; (a) connection of bottom of water column into a very active section or thin waterway ; (e) improper connections between boilers in battery permitting boiler with excess pressure to push water into boiler with lower pressure. '4. Water is carried over into steam main. This may be caused by: (a) grease and dirt in boiler; (6) insufficient steam dome or too small steam liberating area; (c) outlet con- 224 Chapter 13--Boilers f too small area; (d) excessive rate of output; () water level carried higher fn response to operation of dampers. This may be due to: (a) poor oiler . t chimney or breeching; (6) inferior fuel; (c) inferior attention; w (jon of clinker on grate; (e) boiler too small for the load. (fl accummai. . ^ too frequent cleaning offlues. This may be due to: (a) poor draft; '\i'tv'6- rt bustion; (e) too low a rate of combustion; (d) too much excess air in ;t;fae|)OX ca chitUhfraogu'gohffgira*sedso.or. This may be due to: (o) defective draft in chimney Getting of dampers; (4) air leaks into boiler or breeching; (c) gas outlet from or `0CDlT^g^ed with fuel; (d) dirty or clogged flues; (e) improper reduction in breeching hot WATER SUPPLY BOILERS Ti lers for hot water supply are classified as direct, if the water heated ~ through the boiler, and as indirect, if the water heated does not Tririiein contact with the water or steam in the boiler. - -j-Direct heaters are built to operate at the pressures found in city supply '-ns and are tested at pressures from 200 to 300 lb. per square inch. ' The life of direct heaters depends almost entirely on the scale-making i'*ibberties 0f t},e water supplied. If water temperatures are maintained - ' below 140 deg. the life of the heater will be much longer than if higher v^eiperatures are used, owing to decreased scale formation and minimized 'i&rrosion below 140 deg. Direct water heaters in some cases are designed ' ;yt`f ibInudrinrercetfuhseeaatenrds gaernbeargaell.y consist of steam boilers in connection with Vv. heat exchangers of coil or tube heaters which transmit the heat from the steam to the water. This type of installation costs more than a direct : r.system, but has the following advantages: ' i; 1. The boiler operates at low pressure. Water hammer and cold water shocks are -.' /, .''.no' 23t ..trTTanhhesembsicotatielleedristisofpotrrhometeebcdoteiinlderft.hroemhescaatleexacnhdancgoerrroisniown.hich the parts to- which the scale . ,'is attached can be cleaned or replaced. The accumulation of scale does not affect - : efficiency although it will affect the capacity of the heat exchanger. 4. Water hammer due to formation of steam is minimized especially if the steam' 'xl.. . s/up5p. lyDitsocothloerahteioanteor fiswuantdeer rmaauytobmeatpicrecvoenntterodl. if the water supply comes in contact - only with non-ferrous metal. SELECTION OF HOT WATER SUPPLY BOILERS . The size of hot-water supply boiler selected is based upon the quantity ' of water used in 24 hours, the temperature rise, the peak load, the dura tion of peak load, and the size of storage tank used. A boiler capable of delivering per hour 1/24 of the 24-hour demand, operating continuously, would be sufficiently large, but it is good practice to provide at least ; . 20 per cent reserve capacity in the boiler by selecting a boiler which can delivet per hour 1/20 of the 24-hour demand. The storage tank should be of such size that the water stored during off-peak hours, plus the hourly output of the heater will equal the demand during the period of ' peaIfktlhoeads.torage tank is already installed arid is too small, a larger boiler must be used; the boiler having such capacity that the stored water plus 225