Document LJK7kkQYMQ0mzQgJ2dpokrQy7

American Society of Heating and Ventilating Engineers Guide, 1937 Table 9. Typical Calculation op Pipe Sizes on Down-Feed Risers with Flush Tank Water-Closets and Urinals on Top Floor Only (See Fig. 4) Floor of 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 fer 100 Ft 7th and below 8th 4 W. C. 2 U. 3 Lav. 10 10 3 Riser No. 1 789 40 20 9 69 858 21 20 166 172 30 3.3 Pipe Size In. ~~ 2 - 4 7th and below 8th 6 W. C. 4 Lav. 10 3 Riser No. 2 1512 60 12 82 1594 14 14 211 ` 223 30 3.3 4 7th and below 8th 1 S. S. 4 Riser No. S 302 . . 40 4 306 40 121 122 . 30 3.3 2 3 For the second arrangement of hot water risers (Fig. 7b), circulation lines are run back from the last fixture supplied to the main return circulation line in 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 jines must be made about half that used for the cold water risers which dp not have the combined up- 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-Clpsets 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 4 658 Chapter 35--Water Supply Piping and Water Heating regalafc 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. 8th. 4 4W.Q-F.V. 2U.-F.V. 3 Uv- . 4W.C.-FV. 7th. J2L\ 2U.-FV. 3 Lav. 24 2U.-F.V. 6th. r 3U"- 4W.C.-F.V. 3" 2U.-F.V. 5th. ... Top Fixture Connection an. d Air -V-e-n-t'? ^-------- 1 Ii 1 |l 1 1 , 1) II t It 4th. 3- 1 a a 3rd. 3- iaa 2nd. 1st ? 3-Main Fig. 5. Up-Feed System ----n--"-- 1 ht | . 'Ketum Mam ~ 'supply Ma in Fig. 6. Supply and Return Main Connections for Hot Water Supply SirSTEM 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 the 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 659 1 l 1; i1 i l i 1 I ^ j | f j