Exhaust fans
- Thread starter rose1981
- Start date
- Status
- Location
- Massachusetts
Neither or both, it's just a design decision.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Depends on the application. If your system is fixed, as in always the same air volume like for a single room, the flow of a belt driven exhaust fan can be adjusted by changing sheaves. When you have a VAV system (Variable Air Volume), the exhaust fan flow must equal the intake flow to maintain balance. You can't do that with a direct drive fan. But if the volume changes all the time, and it usually does, then it's impossible to keep changing sheaves, so most people with VAV sysetms use VFDs even if they have belt driven fans.
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