Document 6RKLpXM9nJ5KE42aQzXZyZ826

American Society of Heating and Ventilating Engineers Guide, 1937 Return connections to boilers in gravity systems are made the same size as the return main itself. Where the return is split and connected to two tappings on the same boiler, both connections are made the full size of the return line. Where two or more boilers are in use, the return to each may be sized to carry the full amount of return for the maximum load which that boiler will be required to carry. Where two boilers are used, one of them being a spare, the full size of the return main would be carried to each boiler, but if three boilers are installed, with one spare, the return line to each boiler would require only half of the capacity of the entire system, or, if the boiler capacity were more than one-half the entire system load, the return would be sized on the basis of the maximum boiler capacity. As the return piping around the boiler is usually small and short, it should not be sized to the minimum. /Runout. Riser , Wall line. --- - - A ---k IjllilUl n ii 111 HUT' 11 Ulllli!1 ill 1 Swing 1?in H III I mn Ifi ...m.mluII jjoo|inntt^. ^"Runout below floor PtAN With returns pumped from a vacuum or receiver return pump, the size of the line may be calculated from the water rate on the pump discharge when it is operating, and the line sized for a very small pressure drop, the size being obtained from the Chart for Pressure Drop for Various Rates of Flow of Water, Fig. 3, Chapter 35. The relative boiler loads should be considered, as in the case of gravity return connections. Radiator Connections Radiator connections are important on account of the number of repetitions which occur in every heating installation. They must be properly pitched and they must be arranged to allow not only for move ment in the riser but, in frame buildings, for the shrinkage of the building. In a three story building this sometimes amounts to 1 in. or more. The simplest connection is that for the one-pipe system where only one radia tor connection is necessary. Where the radiator runouts are located on the ceiling or under the floor, sufficient space usually is available to make 590 { j ^ ^ (. gigglgbik Chapter 32--Piping for Steam Heating Systems Fig. 8. Connections to Steam-Type Radiator for Two-Pipe System Fig. 9. Top and Bottom Opposite End Radiator Connections Fig. 10.. Top and Bottom Radiator . Connections a good swing joint with plenty of pitch, but where the runouts must come above the floor the vertical space is small and the runouts can project out into the room only a short distance. Fig. 7 illustrates two satisfactory methods of making runouts on a one-pipe gravity air vent system of either the up-feed or down-feed type, the runout below the floor being indicated in full lines and the runout above the floor in dotted lines. Sometimes it is necessary to set a radiator on pedestals, or to use high legs, in order to obtain sufficient vertical distance to accommodate abovethe-floor runouts. Particular attention must be given to the riser expan sion as it will raise the runout and thereby reduce the pitch. Similar connections for a two-pipe system of the gravity air vent type are illustrated in Fig. 8 for the old steam type radiator. If the water type is used, the supply tapping is at the top instead of at the bottom, the runouts otherwise remaining as shown in Fig. 8. A satisfactory type of radiator connection for atmospheric, vapor, vacuum, sub-atmos pheric, and orifice systems of both the up-feed and down-feed types is shown in Fig. 9. While short radiators, not exceeding 8 to 10 sections, may be supplied and returned from the same end as indicated in Fig. 10, the top-andbottom-opposite-end method is to be preferred in all cases where it can be used. On down-feed systems of the atmospheric, vapor, vacuum, subatmospheric, and orifice types, the bottom of the supply riser must be dripped into the return somewhat as illustrated in Fig. 11. On up-feed systems of the vapor and atmospheric types, where radiators in the basement are located below the level of the steam main, the drop to the radiator is dripped into the wet return and an air line is used to vent the return radiator connection into an overhead return line, as illustrated in Fig. 12. When the radiator stands on the floor below the main, tile drip Fig. 13. Connecting Drop Riser Direct to Radiator 591