Document wrVEJRdQyYep73pMO5oVjNR0B

Heating Ventilating Air Conditioning Guide 1939 ventilating units where they are located at an elevation lower than th dry return pipe. Radiators located below the supply main but above th* dry return main may have the drip on the steam drop to the radiato omitted if an overhead valve is used, as shown, in Fig. 14. If they are located above the dry return pipe, they are connected in the manner shown by Fig. 15, which follows the same method as direct radiators similarly located. Convector Connections Convectors are often installed without control valves, a damper being used to shut off the flow of air to retard the heat transfer from the con vector even though it is still supplied with steam. The piping connections for a convector with the inlet and outlet at the same end are shown in Chapter 16. ' Piping for Steam Heating Systems , _. 21 is suitable for atmospheric, vapor, vacuum, sub-atmospheric, orifice systems. pipe Connections for Indirect Heating Units The coils or heat exchangers used to temper the air for ventilation and conditioning are supplied with steam using the same piping principles ^ used for connecting radiators for the given type of system. If the ring coil is located at an elevation lower than the dry return piping, the connection would be as shown by Fig. 22 for a two-pipe vapor system. For a one-pipe system the air line through the thermostatic trap would be omitted and the usual air vent substituted. Fig. 9. Connections to Steam-Type Radiator for Two-Pipe System Fig: 10. Top and Bottom Opposite End Radiator Connections Fig. 11. Top and Bottom Radiator Connections leg M ton 5' lon( Fig. 12. Top and Bottom Opposite End Radiator Connections Fig. 13. Connections to Radiator Hung on Wall Fig. 14. Connecting Drop Riser Direct to Radiator . ' ? Fig. 16. There is no valve on the steam side but there is a thermostatic trap on the return. The damper-for control is shown immediately above the convector. This piping is suitable for atmospheric, vapor, vacuum, sub-atmospheric, and orifice systems of the up-feed type. A similar unit with connections on opposite ends and suitable for the same systems is shown in Fig. 17. This unit has no damper but requires a valve on the steam connection for control. When valves must be located so as to be accessible from the supply air grille, the. arrangement usually takes the form indicated in Fig. 18. A convector located in the basement and supplying air to a room on the floor above may be piped as pictured in Fig. 19 for all systems except gravity one-pipe or two-pipe systems. Convectors with damper control, installed in cabinets or under window- sills, usually are connected as shown in Fig. 20. j , > \ \ J > ;. : J Pipe Coil Connections ; Pipe coils, unless coupled in a correct manner, often give trouble from short circuiting and poor circulation. The method of connecting shown ' 328 Dirt pocket Fig. 15. Piping Connec tions to Indirect Radiators Fig. 16. Convector Con nections Same End Fig. 17. Horizontal Fin-Type Heating Unit \r Cabinet \ type Fin radiator Fig. 18. Heating Unit Valves Behind Grille Fig. 19. Heating Unit with Valves in Basement Fig. 20. Fin-Type Heat ing Unit in Cabinet Where a building is served by a vacuum system or a sub-atmospheric system the air heaters should be piped in the usual manner and traps of large capacity, preferably of the combination float and thermostatic type, should be used. In an orifice system, traps should be used on the returns so that a pressure above that of the atmosphere may be secured on the heaters. A similar connection may be used for a closed two-pipe vapor system using a condensation pump with receiver. In connecting air heaters a branch steam main is directed to the fan room and a single branch is connected to each row of heating units. Each of these branches is split into as many connections as are needed for each row, governed by the number of stacks and width of stacks. Each stack must have at least one steam 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. The return connection should use. a nipple full size of the outlet tapping and reduce the pipe size to the normal return size as required by use of a reducing elbow as shown in Fig. 23. 329