PDFWAC 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 GPMa
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. |
[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapters 19.27A and 19.27 RCW. WSR 22-14-091, 23-12-101, and 23-20-021, § 51-11C-40337, filed 7/1/22, 6/7/23, and 9/25/23, effective 3/15/24.]