The Fantech VT 20M Main Control is designed for use with Fantech Premium Bath ventilation fans. The VT 20M controls an inline whole house fan. Settings can be adjusted as required for your home ventilation needs. An infinite speed control can adjust ventilation fan speed from 0 to 100%. The VT 20M allows an adjustable 0 to 60 minute run time with a 20 minute boost activated by the main touch pad.