The Midwest Hearth thermal switch (also known as a temp sensor or "snap-stat") can automatically control the on/off function of your fireplace blower fan.
TEMPERATURE RANGE: The switch will "close" at 115℉ which allows power to the fan and turns it "on". When the appliance temperature drops to 90℉ the switch will "open" and stop power to the fan shutting it "off".
WHEN USING AN OPTIONAL SPEED CONTROL: Simply set your preferred fan speed on the rheostat and leave it there. When the fireplace reaches 115℉ the blower will automatically turn on and run at the speed you set on your speed control.
LINE VOLTAGE: This switch is rated to run on standard household (plug in) voltage. IE: 115-120 VAC. This is the voltage almost all fireplace blower fans use for operation.
15 AMP MAX: That's 1800 watts at 120v... More than adequate for single and dual fireplace blowers.