Document rp681YQje7bV6LvZKzxrJvz0e

HEATING .VENTILATING AIR CONDITIONING GUIDE 1943 Fig. 12. Supply and Return Con nections for Heating ' Units of Central Fan Systems Fig. 13. Typical Connections to Central Fan System Heating Units Exceeding 12 Sections 306 CHAPTER 15. PIPINC FOR STEAM HEAtlNG SYSTEMS ' _ Two satisfactory methods of making runouts for one-pipe systems for either the up-feed oY the down-feed type are shown in Fig. '4. Where the vertical'distance is limited and the runouts must run above the floor the radiator may be set on pedestals or of the high leg type. A method of connecting a unit heater to a oneTpipe steam heating system is illus trated in Fig. 5. Typical two-pipe radiator or convector connections are shown in Figs. 6, 7 and 8. While the top is the preferred location for the control valve, it may be located at the bottom. Short radiators may. be top supply and bottom return on same end. With convectors the control valve is sometimes omitted and a damper in outlet grille used for heat control. The typical method of connecting pipe coils is shown in Fig. 9 and is suitable for atmospheric', vapor, vacuum, sub-atmospheric, and orifice systems. Typical pipe connections for indirect radiators and tempering or heating stacks are shown in Figs. 10, 11, 12 and 13. Where a building is served by a vacuum system or a sub-atmospheric system the stacks should be piped in the usual manner and traps of large capacity, preferably of the combination float .and thermostatic type, should be used. In the orifice and closed two-pipe systems, traps should be used on the returns so that a pressure above that of the atmosphere. may be secured on the heaters. Each stack should have a separate steam and return connection. Wide stacks are more evenly heated with two steam connections, one at each end, the stacks being divided and a return connection provided for.each steam connection. .For stacks of large capacity it is sometimes desirable to run a separate steam main direct from the boiler to the stacks.-:. PIPE SIZING FOR INDIRECT HEATING UNITS Pipe connections and. mains for indirect heating .units are sized in a manner similar to radiators, but the equivalent direct radiation must-be ascertained for each row of heating unit stacks and then must be divided into the nUmber of stacks constituting that row and into the number of connections to each stack. ,,nK Q X 60 X Ui - <e) _ Q X (ft - <,) . ... 55.2 X.240 . 220.8 (1) where Off = equivalent direct radiation, square feet. . Q- -- volume of air, cubic feet per minute.. ... (e = the temperature of the air entering the row of heating units -under con- . sideration, degrees Fahrenheit. , (i .= the temperature of the air leaving the row of heating units.under considera tion, degrees Fahrenheit. . 60 = the number of minutes in .one hour. . 55:2 = the number of cubic feet of air heated 1 F by 1 Btu: . >; 240 = the number of Btu in 1 sq ft of EDR.'' > ' .. :; - , > 307 /