Wiring Switches for a Bathroom Fan Unit

How are Switches wired for a Bathroom Light and New Exhaust Fan Unit? Wiring Switches for a Bathroom Light and Exhaust Fan Unit, Wiring Two Devices from Separate Circuits on One Switch. © By: Dave Rongey

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Bathroom Exhaust Fan Switches
Electrical Question: How are Switches wired for a Bathroom Light and New Exhaust Fan Unit?

I’m planning to install a light, fan, and heater unit in my bathroom which requires a dedicated 20A circuit.

• Once installed, I’d like to control the lights from this circuit with the lights on a different circuit from a single switch.
• Can I just land the wire from each circuit at the one switch, or can multiple circuits terminate at a single switch?

This electrical wiring question came from: Lou, a Homeowner from NJ, New Jersey.

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

How to Wire Switches for a Bathroom Exhaust Fan

Application: Wiring Switches for a Bathroom Exhaust Fan and Light.
Skill Level: Intermediate to Advanced, Best installed by a Licensed Electrical Contractor.
Tools Required: Basic Electricians Pouch Hand Tools and a Voltage Tester.
Estimated Time: Depends on personal level experience, ability to work with tools and the access to the wiring for the wall switch for the exhaust fan and if a larger switch box will be required.
Precaution: The dedicated combo bathroom exhaust fan circuit, and other circuits in the bathroom should be identified, turned OFF and Tagged with a Note before working with the wiring and installing the exhaust fan switches.
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 Switches for a Bathroom Light and Exhaust Fan Unit

Wiring Two Devices from Separate Circuits on One Switch

• This question addresses a unique situation where two separate circuits will provide the power to two separate devices that will be controlled from one switch. This may be accomplished by installing a Double Pole, Single Throw Switch which has two sets of screw terminals, one set on each side of the switch. Each circuit power source and the device to be controlled is wired separately on each side. This will provide you with the ability to control two devices from one switch.

Wiring Two Devices of the Same Circuit on One Switch

• In another scenario, there may be one circuit that will provide the power to two separate devices that will be controlled from one switch. This may be accomplished by installing a standard Single Pole Switch which has only one set of screw terminals on one side. Connect the power source to one screw terminal, and a lead wire to the other screw, then splice the wire of the two devices to the lead wire.

Wiring Switches in a Typical Exhaust Fan Installation

• Most bathroom fan units require a special type of switch that has multiple switches built into it which will enable separate control for the various bathroom fan functions.
• These switches are designed for one circuit or power source only.
• For a typical installation it is best to install a switch box that will enclose the original light switch and the added circuit and switch for the bathroom fan unit.

More about Wiring a Bathroom Exhaust Fan

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