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. Parts can come loose or erode from high amounts of fan usage while turning the speed up to high can cause a persistent loud hum. 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. A good rule of thumb is to provide one square foot of net free venting area for every 750 cfm.

Also make sure the exhaust of the attic fan is high and near the roof with no obstructions. Whole house fan will only run on high speed i have a whole house fan. When running at a high speed setting does the attic fan run hard or sluggishly. Check the intake for any debris.

Attic fans can sometimes start making noise whether it s humming rattling or making some other annoying noise. 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. You can fix this issue by turning down the settings or checking that the fan is getting enough air. Even at top speed the solar fans only move about half as much air as a conventional electric exhaust fan.

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.