Attic fans help expel hot, humid air from the attic. It also draws in cool, outside air to keep the attic temperatures cooler and more bearable. Attic fans usually connect to a thermostat. The thermostat powers the fan when the temperature reaches a certain setting.
Some attic heat rises as much as 90˚F, even when the day is a lot less cool. The heat will go from hot to cold, and the attic fan will sometimes shift the heat into the other rooms in the home through the vents. As the heat filters down into the home, it places a burden on the heating, ventilation and air conditioning system to keep the rooms cooler. Constant heat build-up can cause the motor in the fan to wear down and malfunction. Most attic fan motors are good for about ten years. In many cases, fan motors stop running or turning.
A well-running fan motor helps you save lots of time and money in energy costs.
To start, gather your tools and material:
- Replacement fan
- Long-nose pliers
- Non-contact voltage tester
- 3/8 inch drill
- Flat-blade screwdriver
- Phillips-head screwdriver
- Pilot bit
- Plastic wire nuts
- Adjustable wrench
- Black, plastic electrical tape
- Switch off the power
Cut off the primary circuit breaker on the panel which supplies power into the attic fan.
- Test the Power
After you switch off the breaker, does a test run to ensure the correct breaker switch is off. A non-contact voltage tester near the fan’s junction box can help determine whether the breaker is off.
Tip: Do not use the humidifier or thermostat to shield you from possible electric shocks.
- Disconnect the Ground Wires
- Next, pull the wires away from the box.
- Loosen the wire screws securing the black, white, green and copper wires together.
- Dislodge both clamping screws from the cable connector.
- Pull the ranch circuit away from the box.
- Remove the ventilation fan
- Use an adjustable wrench to help take the used ventilation fan out of the mounting base.
- Take out the lag screws or nuts that connect the ventilator to the base.
- Position the new fan over the base.
- Fasten it in place with the nuts or lag screws.
- Position the fan
If the fan does not line up with the original hole positions, you may need to re-position the screw or nuts or bolts to the new place. In this case, drill new holes for the bolts, nuts or screws and fasten the fan in position.
- Re-connect the wires
- Fit the circuit cable inside the splice box on the new fan.
- Fasten the clamping screws in position.
- Re-attach the black, white, green or copper ground wires to the fan motor.
- Make sure the color match like colors.
- Align all stripped wire ends side by side.
- Secure the wires together with electrical pliers.
- Give the wires a tight twist, turning them clockwise.
- Use some plastic electrical tape to hold the plastic wire nuts together.
- Although wrapping the wires may not be necessary, it’s a good way to ensure the connections do not pull apart from electrical vibrations.
- Put the box cover back in place.
- Switch on the circuit breaker.
- Check to see if the fan is spinning.
How to replace an attic fan motor
There are times when your attic fan motor may be making strange noises or wear out. If it needs replacing, you’ll need to know how to replace it without too many hassles.
- Take out the motor
Switch off the fan and remove the plug.
Locate the motor at the back of the fan. In some cases, you may need to disconnect the fan from its hole.
Use a screwdriver and remove the back of the fan.
Take out the wires.
Take a picture or make a note to help you re-connect the wires in the right position later.
Loosen the fan motor from the mounting base.
- Connect the new motor
Position the new motor in the fan.
Attach the wires back into the original position with a pair of pliers.
Fasten the wire connections onto the attic fan. Secure it tightly in place and screw on the fan cover.
Apply some tape to help hold the cover in place.
Replacing Gable and Roof Mounting Fan Motors
Some attic fans are either roof-mounted or set up on the gable part of the roof. In larger homes, there may be more than one gable or roof mount fan.
You will need:
- A set of Allen wrenches
Before you begin:
- Safety First: Know the condition of your attic before you attempt any work.
Is the attic high enough for you to stand comfortably?
Do you have enough light to see what you are doing?
Is the attic floor strong enough to hold your body weight?
Are any floor boards missing?
If you’re not sure or satisfied with the condition in your attic, work with a professional instead of attempting to do the work yourself.
- Inspect the fan motor
First, make sure the motor is at fault. Check the circuit breaker, thermostat or humidifier for any underlying problems.
- Disconnect the wires
Locate the big black and white wires that connect the home’s electrical power. Use a voltmeter to measure the voltage across each power line. Check to see if there’s any tripped breaker or any chips in the wiring between the thermostat and the house. If you detect no voltage between the white and black lines, use a flat blade screwdriver and turn the thermostat to the lowest setting.
Measure the voltage again.
If there’s still no reading, switch off the breaker connecting the attic fan.
Test the points with the voltmeter.
When there’s no power in the thermostat, take out the black wire leading to the thermostat. It attaches the black wire going into the fan motor.
Next, switch on the circuit breaker that controls the attic fan.
If the motor is till turning, the thermostat needs replacing.
When the home’s electrical supply which connects directly to the motor fails to turn, the motor needs replacing.
- Measure the motor
Take out the motor and measure it to ensure you buy the correct replacement.
Switch off the power from the circuit breaker.
Test the power supply with a voltmeter and make sure the black and white wires have no electrical current.
Replacing a gable mount motor
- Loosen the wire shield from the thermostat.
- Unfasten the screws that connect the fan motor to the metal shroud in the vent fan.
- Take out the top screw of the fan at last. Leaving the screw to last will help you keep the fan, blade, and brackets together as you disconnect the final screw.
- Next, pull out the whole fan assembly.
When the fan assembly comes out, place it in a cooler site until later.
Take your measurements and notice how the shaft and blades are mounted. It will ensure you assemble the parts correctly when re-connecting the fan and motor.
Locate the nut that holds the fan blade in position at the side of the motor.
Use an Allen wrench to remove the fan. Take out the screws that attach the brackets to the motor.
Replacing a roof-mounted fan motor
It may be a bit more complicated to replace a roof mounted fan than a gable mount fan. Sometimes it’s hard to reach the screws that hold the vent shroud to the supporting struts.
- Loosen the metal shield on the fan motor from the thermostat.
- Take out the screws that hold the structure on the motor with a wrench.
- Take out both screws.
- Next, turn the support struts slightly up and down. Allow enough room to help your move the motor and fan safely.
- When the parts come out, place them in a cooler place to re-assemble later.
- Make a note of how the blades and shaft connect before you remove them from the motor shaft. It will ensure they re-connect in the correct order.
- Locate the nut that holds the fan blade to the side of the motor with an Allen wrench.
- Note that there may be two types of fan motors: Black or white.
- The white motor does not have a starting capacitor, while the black one does.
- The motors may differ in height, but the length of the shaft and diameter are usually the same.
- Take a note or picture of the old motor plate to get an idea of the RPM (revolutions per minute).
- When you get the new motor, connect the fan blades onto the shaft.
- Line up the set screw with the flat side of the motor shaft.
- Secure the set screw with an Allen wrench.
Position the motor
- Re-connect the motor to the roof mount.
- Align the motor in place, so the wires attach to the thermostat.
- Attach the thermostat box to the metal shield.
- Switch off the breaker that powers the fan.
- Attach the black and white wires from the motor to the like colored wires in the thermostat.
- Cap each wire off when you connect them.
- Connect the black house and thermostat wires to each other. Cap them off at the end.
- When all the wires are in place, power the circuit through the breaker.
- Test to see if the fan is
If the thermostat temperature is too cool to power up the motor, check the wiring to see if there are any faults.
Your attic fan works hard to keep your attic space cool and bearable. As heat rises periodically, your attic fan may often shift heat through the vents into other rooms in the home.
Extra heat filtering into the home will require added power from your attic fan to expel the hot air.
Although your attic fan can last up to 10 years, persistent heat building up in the motor can cause it to make strange noises, slow down, or stop running altogether.
A well-maintained attic fan will help save time and energy costs in the home. Replacing the fan will depend on the type of fan you have. Gable or roof-mounted fans may vary, but the necessary steps are just about the same.
Be sure to observe all safety rules and replacement guidelines to keep the process as seamless and hassle-free as possible.