Wire How To: Light Switch

Wire How To Wiring Diagram: Single Switch and Light

Wire How To: Single Switch and Light

This is a typical diagram of how to wire a light switch.  There may or may not be a power out line that feeds something else in the circuit, or there may be more than one power out line, depending on what was handy for the electrician at the time.

CAUTION:
DO NOT EVER WORK ON LIVE ELECTRICITY!  ALWAYS TURN OFF THE CIRCUIT BREAKER BEFORE TOUCHING THE WIRES!  EVEN IF YOU TURN OFF THE POWER, TREAT IT LIKE IT IS STILL HOT!  ELECTRICITY CAN KILL YOU!

Ground Wire:
The orange line represents the ground wire.  This is typically the bare wire or sometimes it’s green.  Not all switches have a ground wire connection, but it is a good idea to have it.  Some older homes don’t have a ground wire in the wiring, so it may not apply.  It’s just an extra safety precaution in case the switch breaks on the inside and somehow connects the hot wire to the body of the switch (wouldn’t that be a rude awakening?).  If the ground wire is connected and that happens, the circuit breaker will see a short circuit and kick off.

Neutral Wire:
The neutral wire is the circuit return path and is normally colored white.  All the white wires should be tied together to complete the circuit, and as you can see, there is no connection on the switch for it.  DO NOT connect them to the switch unless you want to see fireworks (or at least a popped breaker)!

Hot Wire:
The hot wire is typically the black wire.  Tie all your hot wires together to feed the other devices in the circuit, except the one going to the light (called the switch leg).  If there are no power out wires in the box, only the one hot wire coming in, you can just connect it directly to the switch.  If there are other power out wires, you will have to tie them all together and cut off a short piece of black wire and connect it in with the others to supply power to the switch.

It’s always a good idea to twist the wires together with your pliers before screwing on the wire nut to ensure a good, solid connection.  It will help to prevent intermittent problems.

Wire How To Wiring Diagram: Single Switch and Light (alternate)

Wire How To: Single Switch and Light (alternate)

This wiring diagram is for when your power feed is in the light box instead of the switch box.  You’ll notice the main difference being that you use the white wire in the cable going to the switch box as the switch leg and the black wire as the power feed.

Some electricians will tie the white wire in with the power feed and use the black one as the switch leg, but either way, the switch doesn’t care which is which.

Again, I cannot stress enough to be very careful with your connections here.  If you accidentally tie the white wire from the switch into the other white wires in this configuration, there will be fireworks!


Here’s a wiring diagram of a light circuit with three lights hooked up to one switch and an outlet receptacle in the same circuit.  You can hook up as many lights or receptacles together in this way as the circuit will handle.

Wire How To Wiring Diagram: Three Lights on a Single Switch and an Outlet Receptacle

Wire How To: Three Lights on a Single Switch and an Outlet Receptacle

-

10 comments to Wire How To: Light Switch

  • David

    got L1 AND L /N /E IN A LIGHT LIVE COMING IN DO IT GO
    TO L1 AND L TO THE SWITCH

  • Randy

    Hi, David
    It would help a lot if you could provide me with more detail. How many wires are in are in your switch box and light box, and what colors are they? What kind of a light are you trying to hook up?

  • Chris

    Hello-

    Will you please post a diagram or explanation of how to add multiple lights plus a non-switched receptacle? Since I’m bringing power from the attic, I’d like to start at the light box. Thanks very much

  • Gary

    Im trying to hook up a motion sensor light to a porch light but will be further down the line at the end of my house and its switch.. but also want the porch light to activate with it..would it be possible? Im more visual..that reading how to do it

    thx Gary

    • Randy

      Hi Gary,

      Yes, it is possible. You would want to run a piece of 3-wire romex (typically white, black, & red) from the existing porch light to the new one.

      Old existing light junction box:

      Tie all the white (neutral) wires together.

      Disconnect the switch leg (black wire) from the existing light fixture, and connect it to the new red wire.

      Connect the old light fixture black wire to the new black wire.

      New light junction box:

      Connect all the white wires together.

      Connect the red wire as the line (hot) input to the motion sensor itself.

      Connect the black in with the same wire that goes from the motion sensor itself to the bulb socket.

      I hope this helps. If not, let me know and I’ll work on making a diagram.

  • Barry OBrien

    Thanks for posting these light/switch diagrams….they’re the best I’ve found on the web!

  • JB

    Excellent! Thank You for your help! Nice diagrams! You should make more since you are so amazing at making them!

  • Hi,Cheers to the author for giving me some solid ideas

  • Bill

    Hi, I have been search for reasons why when I wire:
    case1: [Power->Light1->Light2->Light3->Switch] it would needs a 12/3 wires between the Lights and in parallel but if I wire
    case2: [Power->Switch->Light1->Light2->Light3] all I needed is 12/2 wires and in series.
    In theory couldn’t I wire case1 in series? What will happen and why shouldn’t I do it? Thanks in advance.

  • Randy

    Hi Bill,
    Yes, you can wire them in series. The one main drawback is if one bulb burns out, they will all stop working and the only way to know which one burned out is with trial and error.

Leave a Reply

 

 

 

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>