Replacing Bathroom Exhaust Fan

Do you know when to replace your bathroom exhaust fan? Typically if it is not doing its job of pulling the moisture out of your bathroom, if its getting noisy or its just old, it may be time to replace it. Now we are going to cover the basic steps for replacing bathroom exhaust fans.

Buying a New Exhaust Fan

First there is the fan sound. You do not want to get a really noisy fan for your bathroom. Fan sound levels are rated in Sones. You want to be sure that the new fan has a Sone rating of 2.5 or lower because 2.5 is considered quite.

Next you need to consider the fans airflow rate. Airflow is rated in CFM or Cubic Feet per Minute. In order to determine what CFM rating you need for your bathroom, you will need to so some simple arithmetic. First we need a standard to go by, so here it is: The minimum ventilation required for a bathroom is 12 changes of total air each hour. There is a formula for figuring out how to accomplish that. The formula is:

    Formula for Optimal Bathroom Ventilation

    Volume / 5 = min. CFM

That is the total volume of the air in the room divided by 5 equals the minimum required CFM for the room. To get the total cubic feet of the room(volume) take the length times width times height.

For example, if you have a bathroom that is 8x8x8=512. Then take that number and divide it by 5, 512/5=102.4 Your minimum required CFM is 102.4 for a small bathroom of 8 feet by 8 feet. So you need a new bathroom fan that can pull over 102 cubic feet of air per minute in our example.

Okay, now you know what you need for your fan. Now think about any extras you might like to have in your fan. These days, fans come with additional heat lamps, lights and even humidity sensors. Now let’s get down to the steps for installing your fan. Since almost any new fan you buy will come with detailed instructions, we will only cover the basics here.

Steps for Replacing your Fan

    1. Turn off the power to your fan from the fuse box or circuit breaker. Try turning it on to be certain you got the correct fuse or breaker. Then check the wires with a circuit tester to absolutely sure.

    2. You may remove the cover from the fan by removing the screws. If it has springs instead of screws, they can be removed by pulling the cover out and pinching the spring until it pops off of the motor housing. Once removed you may be able to see the fan’s serial number and CFM information. If you want to use the same type of fan, write down these numbers and call around to find the same model. This will insure you have no size differences.

    3. Next you remove the fan motor. You may need to access the fan from the attic or crawl space. Remove the screws and if there is a wire harness, take it off as well.

    4. Remove the housing mounting screws and slide the housing to one side to disconnect the duct that vents the fan.

    5. Now lower the fan through the hole.

    6. Disconnect the wires. Twist off the wire nuts. Mark wires if necessary. You’ll need to pull the wires through the strain relief hole to free the housing.

    7. Now you are ready to install the new fan. If you did your shopping correctly, you should have the same size fan. Otherwise you will need to cut the hole as needed with a reciprocating saw or keyhole saw.

    8. Install the new housing and support according to the manufacturer’s instructions. All new exhaust fans come with detailed installation instructions.

    9. Place the new housing up into the hole in the ceiling.

    10. Holding the housing to one side, pull the wires through the strain relief hole and tighten the clamp.

    11. Slide the fan to the other side and attach the air duct with duct tape or a clamp.

    12. Position the housing so it is flush with the ceiling and attach it to the joists with screws.

    13. Connect the white neutral wires, the ground wire and then the black wire and screw on wire nuts and or electrical tape as needed.

    14. Install the wiring cover then connect the fan motor and position it according to the manufacturer’s instructions. Then secure it with the provided screws.

    15. Turn the circuit breaker back on and you are done. Flip the switch and test out your new fan.