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Installing a Occupancy Sensor Switch for a Bath Exhaust Fan

By Dave Rongey - Summary:

Wiring a Motion Occupancy Switch: Wiring Diagram for a Motion Detector Occupancy Switch.

How to Wire a Motion Occupancy Switch for a Bath Exhaust Fan

Electrical Question: I have bought a small extractor fan or exhaust fan which I want to install in my bathroom.

  • I want to make it go on only when people enter the room so I bought a motion occupancy sensor.
  • Can you please explain how I should wire them.


Background: Emmanuel, a Handyman in the UK.

Additional Comments: A very useful site. Keep up the good work!

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

Wiring a Motion Occupancy Switch

Occupancy Sensor

Application: Wiring a Motion Occupancy Sensor Switch.
Skill Level: Beginner to Intermediate – Best performed by a Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience and ability to work with hand tools.
Precaution: Identify the light circuit, turn it OFF andĀ  Tag it with a Note before working with the wiring.
Notice: Installing additional electrical wiring should be done according to local and national electrical codes with a permit and be inspected.
Materials: Make sure the occupancy sensor has the same amperage and voltage rating for the electrical load, and is fully compatible with the electrical circuit and the device it will be controlling.

Installing a Occupancy Sensor Switch in a Bathroom

  • The occupancy sensor or switch is typically installed in the switch box on the wall.
  • The wiring is straight forward except that some of these occupancy sensor switches require a neutral wire for the 120 volt applications.
  • The electrical wiring would be connected with the power source in and load out to the bathroom exhaust fan, a neutral wire if required and a ground wire.
  • Below is one example of a occupancy motion sensor switch wiring diagram which should be helpful.
  • Please read the complete installation instructions for your specific motion occupancy sensor switch for your bathroom exhaust fan.

Wiring DiagramĀ for a Motion Detector Occupancy Switch

occupancy sensor wiring diagram

More about Wiring a Occupancy Switch

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3 Responses to “Installing a Occupancy Sensor Switch for a Bath Exhaust Fan”
  1. Doris Wright says:

    We have a double switch in our bathroom–one for light and one for exhaust fan. We want to replace with a occupancy sensor for light and a timer for exhaust. What is confusing us is the neutral wire. How would we do this?

    • Dave Rongey says:

      Most occupancy sensors require a neutral wire to be at the switch box location. If your occupancy sensor requires a neutral connection then a neutral of the light that you want to control must be in the switch box. If there is not a neutral wire of the light circuit at the switch box then you may not be able to install the occupancy sensor.

  2. pat says:

    I have had an electrician install motion sensors in the powder room and bathrooms to control the exhaust fans. They do not work properly. At the maximum setting the fans do not turn off, at the minimum setting the fans do not always recognize that the rooms are occupied, between these settings the fans will kick on every so often when the rooms are not occupied. I believe the motion sensors are inferior or perhaps defective. Do you have a recommended motion sensor that mounts in the duplex receptacle box?


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