# Question about neutral wire through wall switch



## guitarmonster (Aug 8, 2010)

I live in a house that is about 80 yrs old, so by standard the switch boxes do not have a neutral wire running through them. I am installing a couple of Insteon wall switches that need a neutral wire to operate. My question is pretty simple. When these switches/light fixtures are installed, how are the wires run? I'm assuming that they run the wires up the wall behind the switch, then from the switch up to the ceiling. Or do they literally run the power all the way up to the light, then run 2 more wires to the switch (which seems like more work). I just want to be sure before I spend the money on these switches. 

So basically my question is, if I were to remove the gang box from the wall, would I see the neutral wire running up behind it (that way I could tap into it and run a neutral into the box)?


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## Proby (Jul 17, 2010)

Typically in your situation they would run the feed up to the light and then just a switchloop down to the switchbox. No, you will not find a neutral in the wall behind the switch and even if you did, there wouldn't be enough slack on the cable to splice into it.

What a lot of people do in your situation is connect the neutral of the advanced device to the ground of the switchbox. This practice is why the 2011 code will require a neutral in every box no matter what is installed.


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## guitarmonster (Aug 8, 2010)

I did read about connecting it to the ground, but is it acceptable to electrical code to do that? If not there is an electrical outlet near the switch so I suppose I could just run a new line with a neutral into the box.


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## Proby (Jul 17, 2010)

guitarmonster said:


> I did read about connecting it to the ground, but is it acceptable to electrical code to do that?


 No, it's not legal. It could put objectionable current on your grounding system.


> If not there is an electrical outlet near the switch so I suppose I could just run a new line with a neutral into the box.


Yes, but the right way to do it is to use that new line to power the light. Disconnect the feed from the light inside of the light box in the ceiling.


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## guitarmonster (Aug 8, 2010)

I think I see what your saying, not only run a new line to the switch, but let that new line continue all the way up to the light itself, discarding the entire old line?


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## Proby (Jul 17, 2010)

guitarmonster said:


> I think I see what your saying, not only run a new line to the switch, but let that new line continue all the way up to the light itself, discarding the entire old line?


You would reuse the line going from the switch box to the light box. But up in the light box you would disconnect the line that is currently feeding it.

The reason I suggest to do this is because you don't want current flowing on just one conductor, it could cause metal boxes to heat up. If you brought a new line up to the switch box and only used the neutral and didn't use the hot, it would be against code as far as I know. There are smarter electrician here who could correct me if I am wrong here, but I believe that to be true in this situation.


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## jbfan (Jul 1, 2004)

guitarmonster said:


> I think I see what your saying, not only run a new line to the switch, but let that new line continue all the way up to the light itself, discarding the entire old line?


Thats the size of it.
The only way to get a neutral to the switchbox is another wire.
The only way to add another wire legally is with another cable, so you can run a 3 wire cable to the light, and abandon the exsisting cable.


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## guitarmonster (Aug 8, 2010)

Oh definitely. This wiring is pretty old and in my opinion frightening. So if i'm going to do this i'm just going to run a complete new line and use only the new line to power the light, so I will no longer need the old wiring. So you say I can reuse the wire going from the switch to the light. So let me get this straight. The 2 wires that are going from the switch up to the light itself is the switch loop. I can run a new line to the switch box, which would include the hot, neutral, and ground. I disconnect the old line from the light fixture and cap it off. Then I convert the "switch loop" into the wires that will power the light itself. So now instead of those wires being a switch loop, they are now a neutral and a hot coming from the wall switch?


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## Proby (Jul 17, 2010)

jbfan said:


> Thats the size of it.
> The only way to get a neutral to the switchbox is another wire.
> The only way to add another wire legally is with another cable, so you can run a 3 wire cable to the light, and abandon the exsisting cable.


Yes, a 3-wire from the light to the switch box would work too. Originally I was thinking about just running a new feed to the switch box from the basement. hmmmm

guitarmonster, is there a basement under this room or attic above?


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## Proby (Jul 17, 2010)

guitarmonster said:


> Oh definitely. This wiring is pretty old and in my opinion frightening. So if i'm going to do this i'm just going to run a complete new line and use only the new line to power the light, so I will no longer need the old wiring. So you say I can reuse the wire going from the switch to the light. So let me get this straight. The 2 wires that are going from the switch up to the light itself is the switch loop. I can run a new line to the switch box, which would include the hot, neutral, and ground. I disconnect the old line from the light fixture and cap it off. Then I convert the "switch loop" into the wires that will power the light itself. So now instead of those wires being a switch loop, they are now a neutral and a hot coming from the wall switch?


Yes, that will work. Or, if you have access from above, you can replace that old 2-wire going from the switch to the light with a 3-wire like jbfan recommended. In that situation you would use the black and red as a switchloop and the white as the neutral that you need for your device.


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## guitarmonster (Aug 8, 2010)

Yes there is a basement, very accessible. Now another question, based on what you have said, the line currently runs into the box in the ceiling, where the switchloop is connected and ran down to the switch? The reason I ask is when i'm looking in the box in the ceiling, there are only 2 wires in that box total, I don't see a line coming in, then a switchloop going back out.


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## Proby (Jul 17, 2010)

guitarmonster said:


> Yes there is a basement, very accessible. Now another question, based on what you have said, the line currently runs into the box in the ceiling, where the switchloop is connected and ran down to the switch? The reason I ask is when i'm looking in the box in the ceiling, there are only 2 wires in that box total, I don't see a line coming in, then a switchloop going back out.


So you have a white and black wire coming into the light box and a white and black wire coming into the switch box, is that correct?

What is above the room?


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## guitarmonster (Aug 8, 2010)

Well not exactly. The house is wired with that really old wire, they are both black. The house is over 80 yrs old. When I look in the switch box, I see 2 wires that are going into the box from the top that connect to the switch. In the light box there are just 2 wires connected to the light, that's it and their all black.


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## Proby (Jul 17, 2010)

guitarmonster said:


> Well not exactly. The house is wired with that really old wire, they are both black. The house is over 80 yrs old. When I look in the switch box, I see 2 wires that are going into the box from the top that connect to the switch. In the light box there are just 2 wires connected to the light, that's it and their all black.


Ok, so I assume there is a junction box somewhere. Is there an attic above this room?


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## guitarmonster (Aug 8, 2010)

No there isnt, there is a basement below. However the room does have a suspended ceiling so if I really need to I can cut out drywall since you wont see it anyway.


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## jbfan (Jul 1, 2004)

You are missing a pair of wires.
If you only have 2 wires at the light, and 2 at the switch, the light would not work.
You must have another set of wires for the power from the panel.


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## guitarmonster (Aug 8, 2010)

If I were to run all new wiring, would this diagram (see attachment) be correct? This diagram is basically if I were to run a complete new line, discarding all the old wiring.


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## Proby (Jul 17, 2010)

Yes, that's exactly it.

I am assuming you have a hidden junction box somewhere, that is why you only have two wires in each box.

The light box is mounted in the suspended ceiling or the solid ceiling above it?


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## guitarmonster (Aug 8, 2010)

> You are missing a pair of wires.
> If you only have 2 wires at the light, and 2 at the switch, the light would not work.
> You must have another set of wires for the power from the panel.


I know, the light does work, actually it's on right now. For that reason that's what made me think that the line is running from the basement up the wall, then just the hot wire is run into the box to the switch, and then from there both the neutral and hot run up the wall to the light. Basically the same as the diagram I posted (except I don't think a ground wire is present)


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## Proby (Jul 17, 2010)

guitarmonster said:


> I know, the light does work, actually it's on right now. For that reason that's what made me think that the line is running from the basement up the wall, then just the hot wire is run into the box to the switch, and then from there both the neutral and hot run up the wall to the light. Basically the same as the diagram I posted (except I don't think a ground wire is present)


Yeah, maybe it's old knob and tube.

You are still better off running a new feed up to the switchbox and then running a new cable up to the light box.

Since you have a suspended ceiling, it will be very easy to get a wire into the ceiling by breaking open the wall at the very top (above the suspended ceiling) and then another hole in the ceiling next to it.


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## guitarmonster (Aug 8, 2010)

Ok cool. Yeah I got real lucky with the suspended ceiling and basement, it's real easy to run wires. So I will run a line consisting of ground, hot, and neutral from the basement up the wall, run all three wires through the box, then out of the box up the wall across the ceiling to the fixture, basically running one wire and cutting into the hot (for the switch), and cutting into the neutral (to power the advanced Insteon switch), and of course the ground attaching to the box itself, and connected to the ground on the switch?


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## Proby (Jul 17, 2010)

Exactly.


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## guitarmonster (Aug 8, 2010)

Alright, i'm guessing I should use 14-2 wire?


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## Proby (Jul 17, 2010)

guitarmonster said:


> Alright, i'm guessing I should use 14-2 wire?


Where are you getting the feed from? If you are going to make this a dedicated circuit from the panel, then just make it a 15A circuit and use 14-2. If you are going to splice into an existing junction box, you need to size the wire to that circuit.


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## guitarmonster (Aug 8, 2010)

Im going to run it off of a nearby outlet, which was recently installed by an electrician so it's new. It's on its own circuit which currently consists of just 2 outlets.


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## guitarmonster (Aug 8, 2010)

> If you are going to splice into an existing junction box, you need to size the wire to that circuit.


good advice, I just went into the basement and read the wire. It's Romex 12 AWG rated up to 600 volts, connected to a 20 amp breaker.


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## jbfan (Jul 1, 2004)

guitarmonster said:


> Im going to run it off of a nearby outlet, which was recently installed by an electrician so it's new. It's on its own circuit which currently consists of just 2 outlets.


What size is the fuse or breaker?
If 15 amp, then you can use #14.


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## guitarmonster (Aug 8, 2010)

20 Amp breaker, the circuit is current using 12 awg


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## Stubbie (Jan 7, 2007)

I think all your questions have been answered so here is a diagram of your previous line drawing. I'm not sure which of the two receptacles your wiring the extension from but you get the idea.

I'm showing pigtails at the receptacle you do not have to use pigtails you can just connect to the unoccupied screws with your extension for the light.


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## guitarmonster (Aug 8, 2010)

Ok I just want to be sure on one more thing. When I look at this Insteon wiring diagram, I see wires coming into the bottom of the junction box (assuming it's from the circuit box) and wires going out of the top of the box (assuming that goes to the light). It looks like based on this picture the LINE goes to the light, and the LOAD comes from the box, is that correct?


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## Proby (Jul 17, 2010)

No, Line is the feed and Load is the light. This is the standard.

That drawing doesn't picture the typical box configuration. However, when dealing with boxes you never know how someone wired it so you gotta test it.


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## guitarmonster (Aug 8, 2010)

I knew there was something funny about that diagram. Lets just say when I wire the new line for this, the wire coming from the basement is going into the bottom of the box, and the wire to the light is going out of the top. I just thought it was kind of funny that the diagram is the reverse of that, like your circuit panel is in the attic, and you have a floor that lights up.


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## Proby (Jul 17, 2010)

guitarmonster said:


> I knew there was something funny about that diagram. Lets just say when I wire the new line for this, the wire coming from the basement is going into the bottom of the box, and the wire to the light is going out of the top. I just thought it was kind of funny that the diagram is the reverse of that, like your circuit panel is in the attic, and you have a floor that lights up.


It's good to keep you on your toes because you'll find a lot of stuff that doesn't seem to make sense when you deal with electricity.


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## Stubbie (Jan 7, 2007)

It's also a good idea to pay attention to the type light switch before making a drawing.... my apologies...:icon_redface:

Previous drawing has been corrected


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