Document KJ6OM2xJXZn01mDyN7qMjqoM6

Heating Ventilating Air Conditioning Guide 1939 Table 9. Typical Calculation of Pipe Sizes on Down-Feed Risers with Flush Tank Water-Closets and Urinals on Top Floor Only (See Fig. 4) Floor 07 Bldg. Fixtures on Floor Gpm PER Fixture Maximum Gpm ON Floor Maximum Gpm ON Riser Probable Use (per cent) Probable Demand Riser Gpm Allowable Drop Lb per 100 Ft Pipe Size In. Riser No. 1 7th and below 8th 4 W. C. 2 U. 3 Lav. 10 10 3 789 40 20 9 69 858 21 20 Riser No. S 166 172 30 2 3.3 4 7th and* below 8th 0 w. c. 4 Lav. 10 3 1512 60 12 72 1594 14 211 14 ,223 30 3.3 2M 4 Riser No. 3 7th and below 8th 1 S. S. 4 302 4 306 40 121 40 122 30 3.3 2 3 For the second arrangement of hot.water risers (Fig. 76), circulation lines are run back from the last fixture supplied to the main return circulation linein the same manner as just described, using % in. for the near risers and 1 in. for the far risers. The sizing is much more difficult, as it is necessary to start at the bottom floor of the return riser and work back to the top of this riser and then carry the maximum flow across on to the top of the corresponding supply riser and work down on this riser from the top floor to the bottom. Naturally this gives a much greater flow in the supply riser and aids circulation by reducing pipe friction. The allowable loss per 100 ft in such lines must be made about half that used for the cold water risers which do not have the combined <pp- and down-travel which the hot water must make. In the third and most common arrangement (Fig. 7c) all of the wateris car ried from the tank or heater directly to the top of the building and is there distributed to the risers which are down-feed and may be sized in the Table 10. Summary of Riser Sizes to Given Main Sizes with Flush Tank Water-Closets and Urinals on Top Floor Only. (See Fig. 4) Riser No. 1 2 3 Maximum Gpm Riser 858 1594 306 Maximum Gpm Main 858 2452 2758 Probable Use ' (per cent) 20 10 9 Probable Gpm 172 245 248 Allowable Drop Lb per 100 Ft 3.3 3.3 3.3 Size of Main In. 4 4 4 812 -- Chapter 43. Water Supply Piping and Water Heating regular down-feed manner if the total equivalent run either from the street main or house tank is taken into consideration. The return circulation lines from the bottom of each riser should be arranged in the manner already outlined and any riser not going to the basement to supply fixtures must have these returns carried down to the basement from the termination of the supply riser at whatever level it may end. 4W.C.-F.V. 2U.-F.V. 8th. 3 Lav. . 4W.G-FV. 24 2U.-FV. i * 3 Lav. 7th. 4W.C.-F.V. 24 2U.-F.V. 3 Lav. 6th. 4W.C.-F.V. 3" 2U.-F.V. t t 3 Lav. 5th. 3` 10 lav. 4th. 3' 1S.S. 3rd. 3' ias. 2nd. 3" 1S.S. 1st 3* 3" Main O) Fig. 5. Up-Feed ..System Fig. 6. Supply and Return Main Connections for Hot Water Supply System All risers, both hot and cold, should be valved at the main with an extra check valve on the hot water return circulation so that the risers may be cut off and repaired when necessary without disturbing the service in the remainder of the system. HOT WATER SUPPLY Having designed the service hot water piping, the next step is to furnish some means of heating the water and in this respect it is necessary to pass from the maximum probable flow to the! maximum probable hourly demand, which is quite different. If an instantaneous heater were used, it would require adequate capacity to provide for the heating of the water as fast as it is drawn and a heater of this type should be sized on the basis of the maximum probable flow with the accompanying heavy drafts on tiie heating device and with intervals of no draft at all. To balance these inequalities of flow the storage-type heater is often utilized so that the 813