Wiring a Bathroom Exhaust Fan and Switch

By Dave Rongey - Summary:

How to Install a Bathroom Exhaust Fan and Electrical Wiring for Switches: Do I need a neutral wire between switch boxes for the circuit wiring?

Bathroom Exhaust Fan Switch

Electrical Question: Do I need a neutral wire between switch boxes for the circuit wiring?

  • I wish to install an exhaust fan in my bathroom.
  • There is currently only 1 light (above sink) and 1 outlet in the bathroom.
  • I need to add an exhaust fan and more light so this fan suits the bill.
  • The info I should give you is, the light switch is located outside the bathroom beside the door entering and I will swap it out for a 2 function light switch combination (1 for florescent light in fan and light above sink at the same time, and the other button for only the nightlight in the fan. I will install another switch directly opposite the light switch inside the bathroom to control the fan.
  • The switch I purchased to do this is the Dew Stop FS-100 (hope it actually works) I am quite sure everything is right and my only concern now is do I need that neutral wire between switch boxes?  Pretty sure I do but wondering if it messes up the circuit at all.
  • The other question mark concerning GFCI got answered at the hardware store.
  • I am looking to install this fan as soon as possible, it’s really dark in the bathroom because the only light is on the other side of the wet wall and I have just finished painting the walls and need to get an exhaust fan going.

Thank You very much in advance. Jayme.

This electrical wiring question came from: Jayme, a Homeowner from Ontario, Canada.

Additional Comments: Great idea and very useful and much appreciated tool for homeowners.

Dave’s Reply:
Thanks for your electrical wiring question Jayme.

Wiring a Bathroom Exhaust Fan and Switches

Application: Bathroom Exhaust Fan and Switches.
Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools, sheet rock tools, a non-conductive ladder and a Voltage Tester.
Estimated Time: Depends on personal level experience, ability to work with hand tools and the access to the attic and area of the exhaust fan.
Precaution: Identify the circuit that will be used to power the bath exhaust fan, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Installing additional electrical wiring should be done with a permit and be inspected.

How to Wire a Bathroom Exhaust Fan and the Wiring for the Switches

  • Exhaust Fan Wiring
    When installing a bathroom exhaust fan the overhead or vanity lighting circuit wiring may be used as the power source as long as the fan unit to be installed dies not have additional features such as heating elements which require a new dedicated circuit.
  • Location of the Exhaust Fan
    If the bathroom exhaust fan unit will be installed over the bath tub or shower then the GFCI outlet circuit of the bathroom should be used as the power source.
  • Wiring for Switches
    New electrical codes require a neutral wire in the switch box, therefore extending the neutral wire of the circuit will be essential.
  • Humidity Control and Occupancy Sensor
    The power source for the exhaust fan will require both the hot and neutral wires of the circuit up at the unit and it would be best to have the neutral wire at the switch box as well, especially if the a humidity control switch or occupancy sensor will be installed which requires the neutral wire.

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One Response to “Wiring a Bathroom Exhaust Fan and Switch”
  1. Ed Anderson says:

    I would like to know there to find a limit switch for a bathroom exhaust fan. It is a Fasco model R359


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