How to Install a Bathroom Heater Fan

bathroom heater fan
  • 2-4 hours
  • Intermediate
  • 0-150
What You'll Need
6-foot ladder
Work light
Line voltage circuit tester
Screw drivers
Sheet rock saw
Bathroom fan and heater
Light bulbs

Many bathrooms are cold simply because they lack a heater when it is cold outside. You can improve your chilly bathroom by replacing the existing exhaust fan with a bathroom heater fan. A large variety of bathroom heater fans are available at building supply stores. Bath fan heaters incorporating infra red heat lamps are the most efficient because the radiant heat source does not require a warm up period. This is ideal for short duration occupancy situations such as bathrooms. Also, bathroom moisture will continue to be exhausted without taking the radiant heat with it. This procedure will require attic access.

Step 1 - Calculate the Load and Circuit Capacity

Identify which branch circuit over current and short circuit breaker controls your existing bathroom exhaust fan. Turn the circuit breaker off and on to identify all the electrical lighting and appliance loads connected to the exhaust fan circuit. Total the wattages of all the loads, excluding the old exhaust fan. Calculate the circuit capacity, in watts, by multiplying the circuit voltage times the amperage of the circuit breaker. Now reduce the product to 80%. That is the maximum capacity of this circuit in watts.

Step 2 - Design and Site Considerations

Subtract your total connected watts from the reduced circuit capacity. The difference is the maximum wattage of the bathroom heater fan you can install. Be sure the heater you buy matches the voltage of the existing circuit. Also be certain that the heater you buy is large enough to cover the hole left by the old exhaust fan. This will spare any sheet rock ceiling repairs. Lastly, bathroom exhaust heater fans can vary in the amount of noise they make. Keep this in mind before making your final selection.

Step 3 - Turn the Circuit Power Off

To prevent electrocution, turn the branch circuit breaker off. Confirm it is off by trying the old exhaust fan and using a circuit tester.

Step 4 - Remove the Old Fan

Remove the trim, light bulbs, and wiring cover from the old fan. Disconnect the wiring and the cable clamp. Remove any fasteners inside the fan housing that secure it to the ceiling joist.

Step 5 - Journey Through the Attic

Go through the attic to the bathroom fan and remove the electrical cable and clamp from the old exhaust fan. Remove the 4-inch flexible air duct, and then take off any fasteners securing the old fan to a ceiling joist. Leave the electrical cable for use on the new heater. Completely remove the old exhaust fan.

Step 6 - Install New Bathroom Heater

Install the new bathroom heater fan according to the manufacturer’s instructions. Reshape the sheet rock hole as needed. After completing the installation, turn the branch circuit breaker back on and test your new bathroom heater fan. Warm up to a job well done.