WAC 51-11C-40337. Section C403.3.7 — Hydronic system flow rate

C403.3.7 Hydronic system flow rate. Chilled water and condenser water piping shall be designed such that the design flow rate in each pipe segment shall not exceed the values listed in Table C403.3.7 for the appropriate total annual hours of operation. Pipe sizes for systems that operate under variable flow conditions (e.g., modulating 2-way control valves at coils) and that contain variable speed pump motors are permitted to be selected from the "Variable Flow/Variable Speed" columns. All others shall be selected from the "Other" columns. EXCEPTION: Design flow rates exceeding the values in Table C403.3.7 are permitted in specific sections of pipe if the pipe is not in the critical circuit at design conditions and is not predicted to be in the critical circuit during more than 30 percent of operating hours. Table C403.3.7 Piping System Design Maximum Flow Rate in GPM a Pipe Size ≤ 2000 hours/year > 2000 and ≤ 4400 hours/year > 4400 hours/year (in) Other Variable Flow/ Variable Speed Other Variable Flow/ Variable Speed Other Variable Flow/ Variable Speed 2 1/2 120 180 85 130 68 110 3 180 270 140 210 110 170 4 350 530 260 400 210 320 5 410 620 310 470 250 370 6 740 1100 570 860 440 680 8 1200 1800 900 1400 700 1100 10 1800 2700 1300 2000 1000 1600 12 2500 3800 1900 2900 1500 2300 Maximum velocity for pipes over 14 to 24 in. in size 8.5 ft/s 13.0 ft/s 6.5 ft/s 9.5 ft/s 5.0 ft/s 7.5 ft/s Pipe Size ≤ 2000 hours/year > 2000 and ≤ 4400 hours/year > 4400 hours/year (in) Other Variable Flow/ Variable Speed Other Variable Flow/ Variable Speed Other Variable Flow/ Variable Speed 2 1/2 120 180 85 130 68 110 3 180 270 140 210 110 170 4 350 530 260 400 210 320 5 410 620 310 470 250 370 6 740 1100 570 860 440 680 8 1200 1800 900 1400 700 1100 10 1800 2700 1300 2000 1000 1600 12 2500 3800 1900 2900 1500 2300 Maximum velocity for pipes over 14 to 24 in. in size 8.5 ft/s 13.0 ft/s 6.5 ft/s 9.5 ft/s 5.0 ft/s 7.5 ft/s a There are no requirements for pipe sizes smaller than the minimum size or larger than the maximum size shown in the table.