This unit features a fusible link which will shut off your attic or exhaust fan in unsafe operating conditions exceeding 183 deg F and is also used for the daily operation of your fan as a typical thermostat. This thermostat mounts to a rafter using wood screws and has a wiring diagram provided to complete installation. As a general rule for power attic vents, your normal temperature setting will range from 95 to 115 deg F depending on average regional temperatures, a setting too low will run the fan continuously and a setting too high will result in insufficient air turns for proper ventilation.