How to Extend the Wiring from a 3-Way Switch
The Key to Understanding Light Switch Wiring and Knowing What You Can and Cannot Do
White Wires and Light Switch Wiring
Electrical Question: I am trying to figure out how to finish my circuit. I have a 3 way switch controlling a light(in the middle) where the power(2wire) comes into the first gang box that has the leg going out to the light there. The other switch(on the other side of the room)has been wired to control this light as well using 3 wire. (The white coded as black). Using a double gang box for this second box, I’m trying to add an additional single pole switch and continue power to control another light, but I don’t know where this light’s white return wire should connect to, because the white in the box is coded for hot (black).
This electrical question came from: Jeff, from Richmond, Virginia
See more about Home Wiring for Virginia
Thanks for your electrical question Jeff
Understanding Light Switch Wiring
Understanding how a White Wire is used for light switches can be very confusing, and here is why:
- Just because you see a “White Wire” in a switch box does not necessarily mean that it is a “Neutral Wire”.
- It is often found that the White Wire is actually used for switching the hot, thereby being part of what is known as a “Switched Leg” which is nothing more than switching the hot side of the light circuit.
- In years past and before the days of DIY home wiring, the white wire was used for switching and was not identified with black tape or a black marker which is now required. This was fine for us electricians because we understood this principle.
- To complicate the issue, seasoned electricians know that long ago the neutral wire was used for switching light fixtures, not the hot wire. This practice was discontinued but every once and a while we still find this in some older homes, especially where there is knob and tube wiring.
The Key to Understanding Light Switch Wiring
- What you can and cannot do will be based entirely on how the lighting circuit is wired and where the “Neutral Wire” actually is.
- If you have not installed the electrical wiring then this is best discovered by using a voltage tester.
- Once you have identified the location of the neutral wire you will then know if and how the wiring may be extended to accomplish your desired extension of the circuit wiring , or if it is even possible due to finished walls or available access.
Wiring a Light Switch – Diagram 1
Fully Explained Light Switch Wiring Diagrams. Detailed Electrical Wiring Diagrams and Pictures assist your Home Electrical Projects.
Electrical Wire for the Home
Complete listing of electrical wire types and parts used for home projects with electrical code information serves as selection guidelines.
Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.
Wiring a Switch for an Air CompressorWayne asks:
I am wiring my 240volt air compressor using 10/3 to a lighted 30 amp switch to place by exit door to turn off when im away.
My question is: when I wire the switch I will have essentially two hots, do I place both the black and red on one screw and the black and red on the other?
Also its the lighted Leviton 3032-plr, a lot of the comments say I need to use the neutral to operate the light.
I dont know what to do with that.
Thanks for your help.
Wayne, The Leviton 3032-plr switch that you have described is for 120volt applications and will not work on a 240volt circuit.
A typical 240 volt air compressor requires two hots and a ground wire.
A neutral wire is not required.
A 120volt lighted control switch could be wired as an add on control circuit, however this would require a separate 120volt control circuit, a 120volt lighted switch, and a 120volt control relay with 240volt contacts rated for 30amps.
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