4.750 CFM from an infinitely variable speed EC motor allows you to run this whole house fan all night. 20 inch duct goes to a damper over your ceiling.
![](https://invisco.com/wp-content/uploads/20PROD-blade-and-motor-in-shell-400-wide.jpg)
4.750 CFM from an infinitely variable speed EC motor allows you to run this whole house fan all night. 20 inch duct goes to a damper over your ceiling.