(Effective until February 1, 2021)

PDFWAC 51-11C-40346

Section C403.4.6—Variable flow controls.

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.
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.
2.3. Reset directly by an integral controller based on the relationship between variable speed controller frequency and power.
[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.]
(Effective February 1, 2021)

PDFWAC 51-11C-40346

Section C403.4.6—Variable flow controls.

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.]