How to Replace an Attic Fan Thermostat


Attic fan thermostats serve a two-fold function. The first function is to turn the fan "on" when the attic reaches a certain temperature. This temperature is either preset at the factory or can be set by the end user. This "on" temperature is generally in the range of 90 degrees Fahrenheit ('F) to 120'F. The second function of the attic fan thermostat is to shut "off" under two conditions. The first condition is when the temperature reaches the low end of the thermostat setting. This lower temperature is generally around 80'F. The second condition is to shut the fan "off" when the temperature exceeds 180'F. This high temperature is usually be caused by a house fire. If the fan continues to operate under this type of action it can create a better draft for a fire, causing the flames to spread. By following a basic procedure you can replace this critical apparatus in a few minutes.

  • Obtain the proper specifications from the attic fan before purchasing the replacement thermostat. Most home stores or hardware stores will carry the correct replacement part. Critical information such as voltage, amperage and cubic feet per minute (CFM) should be a consideration in garnering the proper part.

  • Remove the electrical power from the attic fan. This should be done at the circuit breaker panel box. The attic fan should be on its own dedicated circuit and not connected with any other electrical device.

  • Use the screwdriver and remove the protective cover of the thermostat.

  • Use the pencil and paper and record the following information that is set on the two thermostats that are revealed once the cover is removed. The "on" fan temperature and the "off" fan temperature. The "off" fan temperature for the "fire" condition is a factory setting, and you should not have access to make this adjustment

  • Make note of the feeder power wires placement on the screw terminals as well as the fan wire terminations. Different manufacturers will have various arrangements of the wires.

  • Remove the wires and the thermostat using the screwdriver. Position the wires out of your way so you can remove the thermostat from the attic fan housing.

  • Unpack the new thermostat and remove the metal cover. Reset the temperature settings on the new thermostat so they equal the old temperature controller.

  • Mount the new replacement to the attic fan housing and terminate the wires in the proper location.

  • Replace the thermostats cover and apply power. Depending on the attic temperature for the season, you may have to wait until a warm day for a full test of the fan's operation. Some thermostats have a fan "on" bypass, and the attic fan can be tested in this way.

Tips & Warnings

  • Use only proper attic fan replacement thermostats, as common thermostats will not have the high temperature "fire off" feature.

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