How to Wire a Bath Exhaust Fan and Light

By Dave Rongey - Summary:

Installing and Wiring a Bath Exhaust Fan and Light: Power Sources for a Bath Exhaust Fan and Light, Power From a GFCI Outlet, Junction Box Wiring.

Guide to Installing and Wiring a Bath Exhaust Fan and Light

Electrical Question: After my bathroom addition was rough wired and before the insulation was done I decided to add a ceiling fan and light to be controlled with separate switches in place of a simple light fixture.

  • Removing Existing Wiring
    I removed the 2 wire with ground from the switch to fixture and replaced it with a 3 wire with a ground wire.
  • Junction Box Wiring for the Switch
    The box these wires came out of had a 3 wire w/ground coming in from the other switch that was also to control the light via a 3 way switch.
  • Checking the Power Source
    When it came time to finish wire I realized I had no constant power into this box making it impossible to control the fan separate from the light  so I tapped into the outlet circuit that was right under the switch box to supply a constant power source for the bath exhaust fan.
  • GFCI Outlet Circuit
    The problem is that the circuit is GFCI protected because it supplies power to outlets near the sink. Now when I energize the fan it trips the GFCI outlet.

What can I do?

This home electrical repairs question came from: Mike, from Darke County , Ohio.

Dave’s Reply:
Thanks for your electrical troubleshooting question Mike.

Application: Wiring a Bath Exhaust Fan.
Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrician.
Tools Required: Electricians Pouch of Hand Tools for Rough-In Wiring, Electric Drill and Auger Bits and Extension Cord.
Estimated Time: Depends on the extent of the bathroom remodel project, the type of construction and available access to the project area.
Precaution: Any existing wiring in the immediate area that may interfere with the installation of new construction materials should be identified, turned OFF and Tagged.
Notice: Modifying existing wiring or installing additional bathroom electrical wiring should be done according to local and national electrical codes with a permit and be inspected.

Wiring a Bath Exhaust Fan and Light

  • Power Sources for a Bath Exhaust Fan and Light
    The scenario described in this question prevents using the existing light switch wiring because the 3-way switch wiring does not provide the  necessary neutral with the light circuit power source.
  • Power From a GFCI Outlet
    Using the GFCI outlet circuit as the power source will work for the bathroom exhaust fan but make sure you are using the GFCI circuit power source only and not intermixing with any wiring from the existing light circuit wiring.
  • Wiring into a GFCI
    Tapping into the GFCI outlet circuit should be done inside the GFCI outlet box, this way you would have the option to connect to the LINE or the LOAD side of the GFCI to provide GFCI protected or non GFCI protection, depending on the location of the bath exhaust fan in relationship to the tub or shower.

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Consult your Local Building Department about Permits and Inspections for all projects.


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FAQs Frequently Asked Questions and Comments

4 Responses to “How to Wire a Bath Exhaust Fan and Light”
  1. Dave Rongey says:

    GFCI Protection for a Bath Exhaust Fax

    Hi Gary,
    To provide GFCI protection for an exhaust fan the incoming circuit power connects to the Line side of the GFCI outlet, then the wires for the exhaust fan connect to the Load side of the GFCI outlet. The switches for the exhaust fan and light are installed on the Load side wiring as well.

  2. Gary says:

    Wiring a Broan QT140 LE Exhaust Fan

    I have a Broan QT140 LE that I want to put above a shower. It says I need to have it on a GFCI circuit since it will be in a shower. Can I bring the load (power) into the dual wall box and into the load side of GFCI OUTLET and than out (line out in GFCI) to the switch for the fan/light?

  3. Dave Rongey says:

    Hi Vincent,
    Circuit Wiring for a Bathroom
    Check the wiring to the GFCI outlet, specifically wiring to the LINE and LOAD terminals. If the wiring is backwards the the GFCI will not have power at the outlet.
    Identify all of the wiring, both hots and neutrals. Create a diagram if needed, but understand that the wiring connections of the GFCI must be correct.
    I hope this helps,

  4. Vincent Key says:

    I am trying to wire a bathroom. I have power, light, and switch wires coming into the junction box with power going to the switch connected to the vent fan switch and GFCI outlet, and a connection going to another outlet. I have power to light also to vent fan, but not to the GFCI. What could be the problem? When I remove the GFCI and wire the wires together I have a completed circuit.


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