Document Lgk3RGnGBZE7oqvOojB38ar0d

HEATING VENTILATINC AIR CONDITIONING GUIDE .1943 Example 5. Fig. 4 shows a typical down-feed layout with three risers extending eight stories and with the fixtures noted on each floor. This will be solved assuming that the level of the water in the house tank is 30 ft above the fixtures on the top floor, that the length of run from the tank to the farthest fixture is 200 ft, equivalent length of fittings 100 ft, and the pressure required at the fixture is 7 lb. The 30-ft head is equal to a static pressure of 0.43 X 30 or 12.9 lb per square inch and to maintain a pressure of 7 lb at the highest fixtures the drop allowable in pressure is 12.9 -- 7.0 lb or 5.9 lb. As the total equivalent run is 300 ft, this is a drop per 100 ft of 1.97 lb, or practically 2 lb. Therefore, all risers and mains from the top floor back to the tank must be sized on the basis of a drop of 2 lb per 100 ft. Tables 5, 6,7 and 8 show the schedule for Risers Nos. 1, 2 and 3 with the maximum flow taken from Table 1, the per centage of use at the peak taken from Fig. 1, and the probable flow at the peak worked out for each portion of the riser. Riser sizes are taken from Fig. 2, using a drop of 30 lb per 100 ft except on the riser from the top story back, to the tank where 2 lb per 100 ft is the allowable limit. \ Since down-feed risers, are nearly always sized for a pressure loss of 30 lb per-100 ft, it is possible to-arrange useful sizing data in tabular form. Fig. 5 shows a typical down-feed riser for a 20 story building.. Table 9 may be used for sizing such a riser of any height and for any probable flow up to 250 gpm. Table 6. Typical Calculation op Pipe Sizes on Down-Feed Rises with Flush Valve Watek-Closets and Ukinals (Riser No. 8. Fig.,4) Floor op Bldg. Fixtures on - Floor 1st 2nd. I W. C. 2'W. C. 1 U. 1 Lav. 3rd 4 W. C. 2 U. 3 Lav.,, 4th 4 W. C. 2 U.. 3 Lav. 5th 6 W. C. 4 Lav. 6th 6 W. C. 4 Lav. 7th 6 W. C. 4 Lav. 8th 6 W. C. 4 Lav. Gpm ' PER , Fixture 45 45 30 3 45 30 .. 3 . 45 30 3 45 3 45 3 45 3 45 3 Maximum Gpm on Floor Maximum Gpm on Riser . UsageT (per cent) Probable Flow in Riser Gpm Allowable Drop Lb per . 100 Ft. 45 45 100 45 30 90 30 3 . ............. 123 168 58 98 180 60 9. > 30 249 417 180 60 9 31 130 30 249 666 270 12 24 \ 160 30 282 948 270 12 19 v ISO 30 282 1230 ' 16 270 12 196 . 30 282 270 ' 12 1512 14 211 30 282 ' 1794 12 215 2 Pipe Size In. IX 1M 2 2 2 2X . m 4 830 . CHAPTER 46. WATER SUPPLY PIPING AND WATER HEATING Table 7. Typical Calculation of Pipe Sizes on Down-Feed Rises with Flush Valve Wates-Closets and Ubinals (Riser No. 8. Fig. 4) Floor of Bldg. 1st 3rd 4th 5tb 6th 7th 8th Fixtures on Floor 1 S. S. 3 W. C. 1 Lav. 2 Lav. 3 W. C. 1 Lav. 1 S. S. 1 s. s. 1 s. s. 1 s. s. i s. s: Gpm PER Fixture 4 45 3 3 45 3 4 4 4 4 4 Maximum Gpm ON Floor Maximum Gpm ON Riser Usage (per cent) Probable Flow in Riser Gpm 4 4 100 4 Allowable Drop Lb per 100 Ft 30 Pipe Size In. X 135 3 138 142 6 - 148 63 89 6f 90 30 IX 30 IX 135 3 4 142 290 41 4 294 41 4 298 40 4 302 40 4 306 ` 40 119 120 120 121 \ 122 30 30 30 30 2 2 2 2 2 3 Table 8. Size of Distbibution Main foe Down-Feed Systems (See Fig. 4) Riser No. 1 2 3 Maximum Gpm Riser 1038 1794 306 Maximum Gpm Main . 1038 2832 3138 Usage (per cent) 18 9 9 Probable Gpm - -187 ** '255 282 * Allowable Drop Lb per 100 Ft 2 .2 2 Size of Main In. 4 5 It should be noted that the two top floors in Fig. 5 are sized for less than 30 lb per 100 ft. Regardless of the height of the riser being.sized, the two top floors of it should be sized from values given for the top floors of Fig. 5. HOT WATER SUPPLY PIPING The same basic principles used in the design of cold water piping are also applicable to hot water systems. Hot water, like cold water, may be distributed by either up-feed or down-feed systems. It is common practice to provide circulation in a hot water supply system so that hot water may be quickly available when the faucet is opened, -If this is not done,, it is necessary to drain all of the cold water from the' lines between the faucet and the heater, before hot water can be obtained. Three common methods of arranging hot water circulating lines are illustrated in Fig. 6. Although the diagrams are for multi-story build ings, arrangements a and b are also used frequently in residences. A check valve should be provided in the runout from each return riser to prevent temporary reversal of flow in the line when afaueet is opened.- 831