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Control Switch Wiring for a In-Line Exhaust Fan

How is a switch wired for an Bathroom Exhaust Fan? How to Wire a Switch for an Inline Exhaust Fan.


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Wire a Switch for an Exhaust Fan
Electrical Question: How is a switch wired for an Bathroom Exhaust Fan?

My question is what timer or controller do I need with it being low voltage wiring running to each box in each bathroom? The inline fan is a Fantech FR110.

This electrical wiring question came from: Greg, a Handyman from Saint Cloud, Minnesota.

Additional Comments: Very informational

Dave’s Reply:
Thanks for your electrical wiring question Greg

How to Wire a Switch for an Inline Exhaust Fan

This applies to Some Regular Exhaust Fans and Inline Exhaust Fans
Low Voltage Switch Controls for an In-Line Exhaust Fan

Low Voltage Control Switch Wiring for an In-Line Exhaust Fan
Greg, this is a great question and the person who installed this in-line bathroom exhaust fan had a very good idea, as long as the exhaust fan is rated large enough for the square footage and required air exchanges of both bathrooms.

The low voltage control wiring is relatively simple. Understand that low voltage controls are simply a smaller control circuit that activates a larger control relay or contractor. In this case the control wiring is the same for one, two or even more switches located in each bathroom. As you mentioned, there is a low voltage power supply, which will supply power for the control relay. Each pair of wires will act as a switch to control one side of the low voltage power. The low voltage relay is located near the in-line exhaust fan where it will act as a switch for the 120 volt power for the in-line exhaust fan. The low voltage wires are simply wired to a single pole switch. When one or both switches are activated they will in turn activate the control relay which will then turn on the in-line exhaust fan.

Key Components  for a Low Voltage Control System
The low voltage wiring may be installed into an existing junction box if the wiring is rated for 600 volts, which is the rating for typical electrical cable. If the low voltage wiring is not rated for 600 volts then a partition must be installed into the junction box being shared, or a separate switch box must be installed for the low voltage switch and wiring.
The low voltage power supply and control relay must be installed in an accessible area and in an approved electrical junction box or electrical enclosure.
The low voltage wiring and the 120 volt circuit wiring must all be installed according to code.
As always, a project like this must be installed with a permit and inspected.

More about Wiring Switches and Relays:

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FAQs Frequently Asked Questions and Comments

2 Responses to “Control Switch Wiring for a In-Line Exhaust Fan”
  1. Dave Rongey says:

    Hi Jeff,
    Yes – the circuit power, which attaches to the Line side of the Lutron time switch may be spliced with another wire to provide the power for the Line side of an additional switch which may be used independently or separately.
    I hope this helps,

  2. Jeff Phillips says:

    Wiring a inline bathroom exhaust fan with a 2 single pole timer switches(Lutron timer switch with only line and load screws, no other wires), one for each bathroom. My understanding that I can split or twist the source hot wire to the line side for both SP switches. With the hot wire from load side of the switches pig tailed to the load fan. Is this correct and can switches be turned on independently or at the same time?