The FK-165-ESC is a temperature controlled fireplace blower fan kit that is designed to circulate warm air through many hearth products in the industry, and provide variable speed control with a digital control box. Specifically, this is an exact replacement for the Heatilator GFK-4 fan kit. This unit operates on 120VAC, 60 Hz power, and increases the amount of air the fan will circulate through your room from the gas appliance. The increase in circulation will get up to 165 CFM (cubic feet per minute) and allow the room temperature to heat quicker, as well as maintain a consistent temperature-which also improves the energy efficiency of your appliance, saving you on energy costs. The blower fan will automatically turn on a few minutes after the gas heating appliance is ignited and off a few minutes after the appliance has been turned off.