WAC 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.