This CT-DH-1 is designed to turn "On" and "Off" exhaust fans and/or intake fans to remove unwanted atmosphere due to heat or humidity. This device is intended as a cooling and dehumidifying control. This controller is ideal for situations where excess heat and humidity need to be exhausted. Internal sensors will allow a 7 temperature comfort zone and a 7% humidity span (differential) between the time the fans go "Off" and come back "On" again. Plug-in and control circulation fans, exhaust fans, cooling systems, or dehumidifiers. The outlets on the CT-DH-1 are integrated, so that when either the temperature or humidity settings are exceeded, all four outlets will activate, turning "On" equipment plugged into any of the four outlets. If you only want the controller to operate during daylight hours choose to add the photosensor option (P). You may also choose an optional 3 external coil temperature sensor however keep in mind that this will increase the frequency of exhaust cycles considerably. If you are going to use CO2 enrichment or think that at any point in the future you might, choose the CT-DH-3 or CT-DH-4 models. Certifications Free Shipping.