A Power Exhaust is an active, motorized fan system designed to remove return air from the building at controlled volumes. Unlike passive barometric dampers, Power Exhaust systems:
- Actively move air out of the building
- Respond to changes in outside air intake
- Prevent excessive positive building pressure
- Help maintain balanced indoor conditions
When installed properly, a Power Exhaust system supports optimal indoor comfort and energy performance.
However, improper installation or poor setup can create negative pressure, which can draw in unconditioned air through leaky windows, doors, and wall penetrations—causing drafts, hot spots, or humidity problems.
Constant Volume Power Exhaust
A Constant Volume Power Exhaust operates at a fixed speed. It is typically activated when the economizer’s outside air damper reaches a certain position.
Key points:
- Activation is linked to the economizer damper position
- Adjustment is set in the field
- Skilled air balancing is recommended
- Excess air is removed at one consistent rate
While effective in many situations, constant-speed operation may not address varying building conditions or multiple airflow influences.
Modulating Power Exhaust
A Modulating Power Exhaust provides a more precise and responsive solution.
This system uses:
- A pressure transducer (to measure indoor vs. outdoor pressure)
- A Variable Frequency Drive (VFD) (to control motor speed)
The transducer continuously monitors pressure differences and sends signals to th