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554 CHAPTER 21 1957'Giiide Table 1 can be used for pipe sizing by this method. It provides the de signer with a means for quickly assessing the relative effects, economic and otherwise, of various pumps on the system in terms of pipe size. After sizing the. piping on the basis of a preliminary design friction loss the actual friction loss at design rate of flow should be calculated. The friction loss at design flow for all individual sections of pipe and for all fit tings in the longest piping circuit should then be summarized. Table 2 shows the number of elbow equivalents for various fittings: These equivalents can be converted to equivalent feet of pipe by use woo-gris woo-i: : i-io woo-^e 500- .4 5'5<H: - a - -1.0 o 300-J-25 250-|_2o 200- iso-: 30,000-+-3,000 20,000^ r2p00 10,000^ -ipoo -8.0 7.0 6.0 \ HO -5.0 ioo-i re eo- r 5 50- -4 40 2 3,000- --300 ~4.0 2,000- -200 o ut. 35" r3.5 w 1,000-; HOO g * sw 3-- 0 -t-2 ; rj 20 l 1.5 (t '::50 5.5. ? 200t r20 O aI J- 2- 2 So Z I o-J . oz - H O Hi w t5- ** based on clean tubing with i4o r water CO 2 "i4-r -1.0 O -0.9 0.6 -0.7 -0.6 -0.5 Fig. 4. Friction Loss doe to Flow of Water in Type L Copper Tube4 (Based on clean pipe and HO F water) of Table 3. Fig: 7 shows the elbow equivalents for determining friction loss in tees. If the pipe size calculation indicates a required pump head different from that of a standard pump, pipe sizes in the system may be changed to establish a closer relationship between the two. The relation ship between systems and pump heads is discussed in the section Circulating Pumps. If there is more than one circuit in a system, the friction loss for the long est circuit should be used to determine the pump head requirement. Pip ing in the other circuits should be sized to obtain the same total friction loss. Effects of Antifreeze Fluids. Anti-freeze solutions are sometimes used in heating systems when the danger of freezing exists. They should not be Hot Water Heating Systems FLOW OF WATER IN GALLONS PER MINUTE 555 Fig. 5. Friction Loss due to Flow of Water in Iron Pipe T acale 01 chart *3 based on 20 deg temperature difference between flow and return risers. to Had fnction when temperature drop is other than 20 deg, multiply the actual heat conveyed by Vactual temp, drop) and read the "responding friction. Ft per 100 ft Milinches per ft Conversion Ft/(lOOFt) to Milinches/Ft 0.5 1 2 3 60 120 240 360 4 48 5 - 600 used in direct fired boiler application. Corrections'must be made in flow rates, pipe size and pump capacity relative to water `when antifreeze solu tions are used. See Snow Melting Systems, Chapter 23, Panel Heating. SELECTION OF PIPING ARRANGEMENT The type of distribution system selected for any particular building will depend primarily on the structural and architectural characteristics of the building, the need for separate control of different zones, the pressure head due to the height of the building, the space available for piping, and the relative cost of different arrangements of piping. Consequently the loca tion of mains may be considered for basement, for separate floors, or for space above highest heating units. There are four distinct arrangements of main piping: (1) the two-pipe