How to Wire a Double Switch or Triple Switch

By Dave Rongey - Summary:

I want to add another switch or two at one location but I need help with the wiring. Wiring Guide for Wiring Two or Three Switches.

Wiring Guide for Double Switches

Electrical Question: I want to add another switch or two at one location but I need help with the wiring.

  • I moved into a house that has a garbage disposal unit connected under the sink and the ON and OFF switch that is nearby.
  • The previous owner had changed the switch to a two rocker stack or double switch to add a light with the neutral screwed to the switch box.
  • Now I want to add another separate light controlled from the same location so I purchased a three stack rocker switch to control the three devices.
  • Power comes from the outlet where the disposal is plugged into.
  • The diagram shows power attaching to one side and then connecting individually to the three devices.
  • Do I have to re-wire everything to conform to that wiring diagram.
  • The way it is now, I can get either the two lights or the disposal to work, but not all three together. What I have to do?

This home electrical repairs question came from: Jaime, from San Juan.

Additional Comments: Excellent website. I learned a few tricks browsing thru your answers. I’ll keep it handy from now on.

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

Wiring a Double Switch or Triple Switch

Application: Wiring a Stack Switch for a Garbage Disposal, or a Triple Switch which can be used for a Broan or other brand Exhaust Fan.
Skill Level:  Intermediate to Advanced – 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 tools.
Precaution: Identify the circuits, turn each circuit OFF and  Tag them with a Note before working with the stack switch wiring.
Notice: Installing additional electrical wiring should be done with a permit and be inspected.

Electrical Wiring for Double Switches and Triple Switches

A stack switch, double switch, or triple switch can be wired a few different ways depending on the wiring configuration and desired level of control for exhaust fans or other devices.

  • One Power Source
    • If there is only one power source that will power the separately controlled lights or devices then the single power feed wire attaches to one side of the stack switch where there is typically a bridge or metal link enabling all of the switches to share the single power source.
  • Multiple Power Sources
    • If there is more than one power source then the bridge must be removed to enable the separate power sources to attach to the appropriate screw on the power side of the stack switch.
  • Wiring Separate Functions
    • The wiring leading to the separately controlled devices is then attached to the opposite side of the stack switch.
  • Grounding the Switch
    • The stack switch should be grounded with the circuit ground wire or with a grounded metal switch box.
    • Stack switches are typically available in the toggle switch style or the flat rocker type or decorative style switches.
  • Amperage Rating of the Switch
    • The amperage rating of the stack switch will be either 15 amp for number 14 AWG copper wire or 20 amp for 12 AWG copper wire.
  • Garbage Disposal Applications
    • Garbage disposals require a lot of power to operate and a 20 amp rated switch will last longer than a 15 amp rated switch.

Important Note about Neutral Wires

  • Switch Boxes
    • This question described what leads me to believe that a neutral wire is attached to what may be a grounded metal switch box.
    • If this is true then this is not safe and should be removed and the correct wiring provided with a separate insulated neutral wire for the circuit.
    • If this is not true and the white wire is a jumper wire from the switch ground to the grounded metal switch box then the white wire is being used for a ground wire and will need to be colored green with green electrical tape or a green permanent marker.
  • Ground Wires and Neutral Wires
    • The concern here is that a ground source or ground wire can not be used for a neutral wire – this practice is highly dangerous and can produce electrical shock hazard conditions in the home electrical wiring system.
    • If you are unsure about the wiring then please consult a licensed electrician who will make the appropriate checks and wring adjustments as necessary for a safe connection and operation.

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Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all projects.

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