Document 2jOLBq1woOM8BGOw1nmx68oe6

846 CHAPTER 53 T 965 Guide And Data Book 0.'Steel of Flues. a. The cross-sectional area of smoke flues shall be designed and proportioned to meet the conditions of temperature, within and without flue, thickness of masonry, exposure, shape material of flue, and other influences. The National Braiding Code specifies lined chimneys and metal smoke stocks for all gas appliances which may be con verted readily to'the use of solid or liquid fuel, mid also for all boilers' and furnaces, except.those having a flue-gas tem perature not exceeding 550 F at the outlet of-the draft hood when burning gas at the manufacturer's rating and which may; therefore, be 'connected to Type -B vent piping. Ap proved Type B vent piping is noncombustible, corrpsion-re dstont piping of adequate strength and heat-insulating-value, having bell and spigot or other' acceptable joints Fig. 4 may be used for selection of vent-pipe Important points to be considered in the use of Type B vent piping are: ................................ '- 1. Type.B Aims must be plainly and permanently marked.at the point where the vent connection enters the flue: For Use on Gas Appliances Only. 2: Type B gas vents shall be installed with a clearance to combustible material or construction, whether, plastered or un plastered, of not less than one inch, provided that for vents of floor furnaces, such clearance shall be not less than' 3 ft' from the outlet of the draft hood, measured along the center |inft of the vent'piping. '- . Other.important points that should be considered for flues and vents for gas appliances are as follows: -1. Clearances from combustible' inaterial to gas appliance vent piping other than approved Type B gas vents shall be' in accordance.-with the Braiding Code Standards of the Nation^ Board of lire Underwriters for the Installation of Heat Produo* ing Appliances. Heating, Ventilating, Air-Conditioning, Blower, and Exhaust Systems. . 2. Every flue-connected.appliance, except an incinerator, un less its construction serves the same purpose, shall.be:equipped with an effective draft bood which either (c) has been approved as part of the appliance or (b) complies with nationally recog nized standards for, draft,hoods. The draft bood'shall be at-f tached to the flue collar pf.the appliance'as conditions permit^ and in a position for*which it is designed with reference to'horizontal and`vertical planes. The' draft hood Bh*11 be so located that the relief opening is nbf obstructed by any port of the appliance or adjacent, construction. 3. No vent pipe from a gas appliance be interconnected with any other vent pipe, smoke pipe, or flue, unless such, gas appliance is. equipped with an automatic, device to prevent the escape of unbumed gas at the main burner' or `burners,' .Where a gas appliance vent pipe is joined with A smoke pipe from an appliance burning some other type of'fuel, for connection into a single flue opening, they dial! be joined by a Y fitting located as close as practicable to the chimney. With'liquefied petroleum gases, the automatie device to prevent the'eseape'of unbumed gas shall shut off the pilot light, as well as the'inain burner or burners. ... . -Tests of masonry chimneys9 made of a variety.of materials have developed-additional w^mm^ndatinnw -warding construction of masonry.chimneys ;that..will [decrease-,the hazard to surrounding combustible-materials. . / . ':7' references; v; /;\;5 1 Criteria Used in the 'Examination of Applications for Pennies to Install Oil Fired Equipment in the Cuy of New York (N. Y. De partment of Air Pollution Control,.January 1959). , * Journal of the Air Pollution Control Association '(November 1959, p: 150). --t.:--. - `S. Konzo: Chimneys. and draft (IFtnter Air Conditioning, , ... ,. .,,.7National Warm Air Heating and Air Conditioning Association. 1939, Chapter 32).. * A. G. Wilson: 7 Influence' of the house',on chimney draft (ASHRAE Transactions,'VoL 07, 1961,p. 317). * D. W. Locklin: Chimneys, .Vents and Combustion Air Supply {American - Petroleum ^-Institute, API Publication No.' 1537, January .1960). . . .... .j, * L.' B. Schmitt and R- B. Engdahl: Performance' of residentikl chimneys (ASHVETransactions,'VoL 55, 1949, p.- 241). I R. H.-Sherlock and B. A. Stalker: A Study of`Flow-.Phe nomena in the Wake of Smokestacks (University oJ;Mlchigan, Z>- partmeni of Engineering Research Bulletin No. 29, 1941). . i . 1 R. S.Dill, P. R. Achenbach, and J. T. Duck: Observed per formance of some experimental chimneyB (ASHVE Trans actions, Vol. 48, 1942, p. 351). ' ' *-1 - * P. R. Achenhach-and S. D. Cole: Performance of- fourteen masonry chimneys under steady state conditions (ASHVE Transactions, Vol. 55,1949, p. 129)...... . i* R. D. Thulman and W. H. Shenkle: A theoretical aridex- perimental investigation -of the performance of- some'short flues under.*steady-state conditions CThesb at Massachusetts Insti tute of Technology, June 1951J. u E. H. Perry: Gas Vent Tables' (American Gas Association Laboratories, Research Report No. 1319, December 1960). M American Standard Installation'of Gas 'Appliances and Gas Piping (American Standards Association, Z21.30-1959). II Comfort Heating (American Gaa 'Association, 1938, p. 71). ." C. G. Segeler: Sizing.of Chimneys and Flues Used for. Gas Appliances (American Gas Association,'Sixth International.Gas Conference, 1955):'' *' ' .. " J. G. Mingle: Draft and Capacities of Chimneys (Combustion Publishing Co.,-New York, 1925,.p. 134)...,. < ... "LF. Moody: Friction factors for.pipe flow (ASMS Trans actions, Vol. 66, 1944, p. 671). ........ ` '11 R. T. Kent (ed.): Mechdnical',Engineers*' Handbook (John Wfley A Sons, New York). ` ** G. A.' Hool-and' N: C. JohnaoaV-Handbdok'cf Building Con- sfrucrion'(McGraw-HillBook Co., New York,'1929).- u P. R. Achenbach: Physics of chimneys - (Physics Today, Vol. 2, December 1949);- - ' ~r< ' ' * ` " R. K. Thulman: Performance of Masonry. Chimneys for Houses' (Housing and'Home Finance-Agency'TVeAmcal-Paper No. 13, August 1949), a CSlOl-43 OH-Buming Space Heaters Equipped vmih Va porizing Pot-Type Burners,. CS75-42-=Automattc.Mechanical ,0U Burners Designed for,, Domestic Installations, CS(E) 104-43 Warm Air Furnaces Equipped until Vaporizing Pot-Type Burn ers, CS109-44 Solid-Fuel Burning Forced Air Furnaces, CS113-44 Oil-Burning Floor' Furnaces Equipped with .:Vaporizing Pot- Type Burners (National Bureau of Standards Commercial Standards). **-N.D. Mitchell: Fire'hazard tests with masonry chimneys (National Fire Protection Association Quarterly, -October 1949). 4^ .- >'*' CHAPTER 54 ' ' ' `1" UNIT VENTILATORS AND UNIT HEATERS l/nfl Ventilators: ChssrlKafion, Ratings, Capacity, Requirements! Appficofion, Control, Location, Exhaust Vents, Window Downdraft Prevention, Mechankai Cooling} Unif^Heaters:.ChssrRcatioh, Application, Heating Medium, Type, Location, Sound Level, Ratings} Control, Piping, Maintenance NIT ventilators and unit heaters are discussed in this 3. Arrangement of Elements. Unit ventilators may be .of U chapter. The types, characteristics, method of rating, the (a) draw-through, or (b) blow-through arrangement Fig. 1 shows a typical draw-through unit and Fig. 2 snows.a typical and procedures for selection arid application of these prodblow^hrough .unit ' ............ ucts are described. Air Capacity Ratings of Unit Ventilators ... UNIT VENTILATORS Unit-ventilators are customarily cataloged with.two'rat The term unit ventilator denotes an assembly, the principal ings, .the stasidard 'air rating and the anemometer air rating. functions of which are to heat, ventilate, and cool a space by . The standard air rating is obtained in accordance with the the introduction of outdoor air in quantities up to 100 percent ASHRAE Standard Code for Testing and Rating.Steam Unit of its rated capacity. The heating medium may be' steam, hot water, gas, or electricity. The essential components of a Ventilators.* -This .code .requires 0 F entering air .temper ature, unit fan operating at rated speed with-standard.louver unit ventilator are: fans, motor, heating element, dampers, or grille on the outlet, and dry saturated steam at a temper filters^' and outlet grilles (or diffusers),' all encased in a housing. `The second type of unit ventilator is similar to the first, but, in addition to their normal winter season functions of heating, ventilating, and cooling with outdoor air, they are equipped to cool and dehumidify during the summer season. They are usually arranged andcontrolledto introduce a fixed quantity of'outdoor air for Ventilation during occupied periods in warm weather.' Besides the elements listed above, they are usually furnished with'Hot'and chilled water'heatingrcooling ature at the unit corresponding.to a pressure of 16.7-psia (218.5' F). The standard air rating of the unit is.the delivery in cubic feet per minute, converted to standard air at.70.F. The anemometer air rating ,is .peculiar to school venti lation. It originated as a convenient field measurement for eheelring air quantities, and is' the bass of rating for venti lation requirements under -some state and local' building codes. The anemometer rating (air capacity) is obtained by averaging the air. velocities, obtained by an anemometer (propeller or averaging type), held over equal subdivisions coils and condensate drains. Their application is described in the section iYear-round Unit Ventilators. . ` 'Unit ventilators are* used primarily in schools,, meeting rooms,' offices and other areaswhere the density of occupancy indicates the need for controlled ventilation. .The typical unit is equipped with a system of control that permits the heating,-ventilating, and cooling'effect-to be varied while the fans are operating continuously. In Dormal operation, the discharge air temperature from a unit is varied in ac cordance with the room requirements. When heating is required, the air delivered is above room temperature. .When the heat' generated within the'room by'occupants, lights', sun,' etc., is sufficient to exceed the heat losses, the tempera ture of the air delivered is below.that of the room. It is.cus tomary' to equip'unit .ventilators withcontro! devices that, prevent the delivery of air at a temperature low enough to cause discomfort. Classification The various' types of unit ventilators can be classified according to .the three following methods: 1..Heating Medium. Four types' of heating- elements are used: (a) steam, (b) hot water, .(c) gas-fired, and- (d)z-electric. - 2. Type of Unit. Under thia classification there ,sre - three basic types to be-considered: (a) floor-mounlcd type, (b) ceiU mg-mounted type, and (c) auditorium type which b .UBed in vertical, horizontal, or inverted positions. Figs- 1 and 2 show typical fioor-mbxmted units. Fig. 3 shows a typical cedingmounted unit, and Fig. 4 shows a typical auditorium-type unit m horizontal position. Tbe ceaeral reapocuibility for this chapter is assigned to TC 3.1, Hot Water asd 8team Resting. 847