How to Wire a Light Switch
Diagram 1

Wiring a Single Pole Switch

Question: Your example shows 2 wire Romex but most Romex I have seen has three wires one white-one black and an un-shrouded copper ground wire. What is the correct connection for this ground wire?
Jerry,

Answer: As explained in this page above: These Type-NM cables contain a ground conductor which is required for all applications as well. The ground conductors are always bonded together to insure the integrity of the ground path.
Dave

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Questions about Wiring Switches

Question from John in Lexington, Kentucky:
How is the Wiring for a New Light Switch and Fixture added to an Existing Switch?

I have an existing light switch, and I want to add a second switch for a new light that will be operated separately. The power comes into the switch which operates a single light at the end of the circuit. I know I have to change the gang box and I’m fine with running cable and installing plates but I’m not clear on the best way to add the wiring. Is there a simple way to do this or should I get an electrician?

Dave’s Answer:
Adding a Light Switch and Fixture to an Existing Switch

The task of installing additional wiring for a light switch and new light fixture will depend on available access to the proposed location. Hiring a qualified electrician will ensure that the installation is performed correctly where the existing circuit wires will be identified, and new circuit wiring will be extended to the new light switch and then out to the new light fixture. The method used to install the new wiring will depend on the wall structure and location in the home. Special attention will be given to the existing circuit capacity, the wire type and size, as well as making sure the additional wiring is protected and installed according to all the electrical codes that will apply.

Question from Denny, a Handyman in Sudbury Ontario Canada, Canada:
How do I close off an existing light and add two new lights off of the existing light switch?

I have a single light on a single switch in my kitchen ceiling. I want to close off the existing light and run two new lights off of the existing light box. It is not far from the existing light, so will I need to run wire from existing box to the two new boxes. How do I wire it considering I don’t want a light fixture in the current spot. How do I close it off?

Dave’s Answer:
Adding New Light Fixtures off an Existing Light Switch

The easiest way to add new light fixtures is to run the new wiring to the existing light fixture, splice the wires together as the old fixture was connected and then place a decorative blank cover over the fixture box. Arlington makes a white blank fixture box cover that works very well for this type of application.
If you would like to remove the light fixture box, and there is access to the attic area then the fixture box could be removed, and the wiring installed into a new junction box located in an accessible location where the new wiring for the additional light fixtures may be connected. The new junction box must be securely mounted and an blank cover must be installed after all the wiring connections have been completed.

Question from Rob, a Homeowner in Ottawa Canada:
I have what I am sure is a simple question, but I want to be sure as the new light switches I want to install are expensive digital switches.

The new switches are obviously meant to be 3-way as they have a Red wire in addition to Black, White, Green. The old switches are not 3-way though and the electrical box they are in does not even have RED wires. The one old switch is the only switch controlling one light, while the other old switch is the only switch controlling three other lights.

So when I put the new switches with the Red wires in the box, what do I do with the Red wires?

My guess would be that I just cap off the Red wires from the new switches as they are not needed, but I do want to be sure.

Dave’s Answer:
Spare Switch Wire

You are correct, when s new switch will not be used as a 3-way switch the Red wire is capped off with a small wire connector or electrical tape.

Question:
Can one single pole switch control another single pole switch?

Dennis from Denver, Colorado asks:
Under the International Electrical Code, is it permissible for one single pole switch to control another single pole switch? The original intent was to have three-way switching which didn’t happen.

Answer:
Two single pole switches controlling each other and a light fixture would not function correctly therefore technically it would not be compliant with electrical codes. In a situation such as this you should consider the option of installing a matched pair of Master and Slave switches which will act just like two three way switches. This type of switch may be found at most hardware stores or electrical supply distributor.

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