C403.4.6 Variable flow controls. Individual pumps required by this code to have variable speed control shall be controlled in one of the following manners:
1. For systems having a combined pump motor horsepower less than or equal to 20 hp (15 kW) and without direct digital control of individual coils, pump speed shall be a function of either:
1.1. Required differential pressure; or
1.2. Reset directly based on zone hydronic demand, or other zone load indicators; or
1.3. Reset directly based on pump power and pump differential pressure; or
1.4. Reset directly by an integral controller based on the relationship between variable speed controller frequency and power.
2. For systems having a combined pump motor horsepower that exceeds 20 hp (15 kW) or smaller systems with direct digital control, pump speed shall be a function of either:
2.1. The static pressure set point as reset based on the valve requiring the most pressure; or
2.2. Directly controlled based on zone hydronic demand; or
2.3. Reset directly by an integral controller based on the relationship between variable speed controller frequency and power.
[Statutory Authority: RCW
19.27A.025,
19.27A.045 and chapter
19.27 RCW. WSR 20-21-080, § 51-11C-40346, filed 10/19/20, effective 2/1/21. Statutory Authority: RCW
19.27A.020,
19.27A.025,
19.27A.160 and chapter
19.27 RCW. WSR 19-24-040, § 51-11C-40346, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW
19.27A.025,
19.27A.160, and
19.27.074. WSR 16-03-072, § 51-11C-40346, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW
19.27A.020,
19.27A.025 and chapters
19.27 and
34.05 RCW. WSR 13-04-056, § 51-11C-40346, filed 2/1/13, effective 7/1/13.]