The Verasys COBP system controlled by SMART Equipment controllers support three types of power exhaust: constant volume EF, modulating exhaust damper, or VFD exhaust fan.
Economizer Damper Position for Exhaust Fan to Turn On: The constant volume exhaust fan turns on when the supply fan is running and the economizer is open more than the setpoint.
Economizer Damper Position for Exhaust Fan to Turn Off: The constant volume exhaust fan turns off when the supply fan is off or when the economizer is open less than the setpoint or 10% open, whichever value is greater.
The exhaust damper modulates to maintain the static pressure setpoint for the building. When the exhaust damper opens more than the Exhaust Damper Position for Fan to Turn On setpoint, the power exhaust fan turns on. When the exhaust damper is open less than the Exhaust Damper Position for Fan to Turn Off setpoint, the power exhaust fan is turned off or 10% open, whichever is greater.
The VFD exhaust fan modulates to maintain the building static pressure setpoint. The power exhaust fan turns on when the supply fan is on. The exception is when the building static pressure is 0.02 in. (0.508 mm) W.C. or more below the setpoint and the VFD exhaust fan is at 0%. The power exhaust fan turns on again when the building static pressure is 0.02 in. (0.508 mm) W.C. or more above the setpoint.