Attic Fan Does Not Run On High Speed

Fans are rated by cubic feet of air per minute or cfm.

Attic fan does not run on high speed.

In order to get rid of the hum you need to either operate the fan at a low speed or replace the fan with a new one that has more blades. Whole house fan will only run on high speed i have a whole house fan. Check the intake for any debris. If it is rotating slowly or not producing a lot of air in the high speed setting you may have a problem with the exhaust or intake.

Also make sure the exhaust of the attic fan is high and near the roof with no obstructions. The attic fan tends to makes a humming noise when it has a few blades and is running at a high speed setting. These fans do not run nearly as well as a standard electrical attic exhaust fan which can run into the night while trying to cool the attic. You can fix this issue by turning down the settings or checking that the fan is getting enough air.

For years since we bought the house 10 years ago when we turned the fan on low it turned on high first before settling on low within a matter of a second or two. Even at top speed the solar fans only move about half as much air as a conventional electric exhaust fan. One major variable is the venting if you plan on running the fan on high speed most people do you need to make sure that there is at least enough exhaust venting for high speed setting. A good rule of thumb is to provide one square foot of net free venting area for every 750 cfm.

The cost of electricity of running a standard attic exhaust fan is probably less thant 5 10 a year.