For total control of your HRV/ERV system, this Triple-Function Wall Control by Fantech is the best way to go. To run your HRV/ERV at a continuous low speed, press the button once - resulting in a green light. Press the button twice to make the light yellow and the unit will run 20 minutes on/40 minutes cff, repeating continuously. Pushing the button three times results in the system running continuously on high speed, with a red light. Use this control in one central location to keep your house balanced.