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Old 07-26-2010, 11:56 AM   #1
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use neutral wire from another circuit?


I'm replacing a few of my 3 way light switches for 2 way insteon Home Automation switches. These switches need a neutral (white) wire to send/recieve signals.

I sucessfully wired the switches as 2 way but plan on using a neutral wire from an outlet on ANOTHER circuit to connect these switches to neutral. Is this okay? Everything seems to work fine but i'm getting voltage on the neutral wire, Is that normal and okay? I'll attach a sketch of the setup if it'll help.
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Old 07-26-2010, 12:00 PM   #2
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No, you can't pull the neutral from another circuit



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Old 07-26-2010, 12:09 PM   #3
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Aren't all the neutral's just connected together in the circuit panel?

there are 3 switches on 2 circuits. So if I run new common, I'd need to run 2 seperate common's from the breaker to the switches on each circuit?

I guess I don't see the logic since they're all connected together in the end.
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Old 07-26-2010, 12:24 PM   #4
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Quote:
Originally Posted by justinm001 View Post
Aren't all the neutral's just connected together in the circuit panel?
Yes, they are connected to a bus and feeder cable that is sized to handle the current available.

When you use the neutral from another circuit, you now have the possibility of putting not only the load of the original circuit on that neutral, but the load of the second circuit as well. For example, you might now be putting 40 amps thru a #12 wire.

As for your situation, is it code compliant? Nope. Would it really hurt? Nope. Most people end up connecting that neutral for the device to the ground in order to get it to work, which is why the 2011 code will require a neutral be ran to every box, whether it's needed or not.
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Old 07-26-2010, 12:36 PM   #5
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Now i understand. I'll try to find the correct neutral wire comming to/from that circuit and wire it correctly.

What is the easiest way to find the neutral wire from that specific circuit? That circuit only has ceiling lights on the floor.
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Old 07-26-2010, 07:58 PM   #6
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If you had a working regular 3 way switch setup and you wanted to convert to 3 way dimmers or electronic master salve 3 way control, you should be able to do that without hooking into a neutral of another circuit and without stringing more wires.

There are 3 wires going between the swtiches. One will become the neutral. One will become the hot feed. One will become the communications line for the switches. There will be a terminal on one or both switch units to connect the (switch controlled) hot wire for the lights. Put a/the switch unit with that output terminal in the box where the light cable enters.

There is supposed to be only one neutral path from any light or receptacle back to the panel and the neutral has to accompany the matching hot wire.
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Old 07-26-2010, 08:13 PM   #7
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He might have a dead-end 3-way in which there won't be a neutral in the other box. That's how I took it.
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Old 07-26-2010, 08:28 PM   #8
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If you do end up doing this, do yourself a favor and whatever circuit you took it from, move the breaker next to the other circuit, and make it a double pole, make sure you get 240v from both screws. There is no chance of overloading the neutral this way because if both circuits are at full load, the neutral will be 0.

But if there is any possible way (which I'm sure there is) you can avoid this, then do avoid it.

Also good to know about the new code coming out. I don't know if it will apply to Canada, but I will keep it in mind next time I wire something.
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Old 07-26-2010, 09:48 PM   #9
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Quote:
Originally Posted by OnThePike View Post
Does this mean the end of black taped white wire switch loop?
You got it! If you want to run a switch loop down, you would have to run a 3 wire and just cap off the neutral. It also means the end of dead end 3-ways unless you are going to use a 4 wire..

When doing ceiling boxes, I always like running the feed to the ceiling and a switch loop down. It allows you to have both a switched hot and constant hot in the ceiling box, which aids in the use of a ceiling fan later.
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Old 07-27-2010, 05:52 AM   #10
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Quote:
Originally Posted by Proby View Post
He might have a dead-end 3-way in which there won't be a neutral in the other box. That's how I took it.
A dead end 3-way also has a 3 wire cable going to it where the former travelers and switched return become hot, neutral, and control.

Now with electronic or remote control switches or master/slave dimmers, the module that actually controls the light must be in the box with a feed to the light. Certain 3 way setups with the travelers going through the light box down to both switches won't work with the new hot, neutral, and control wire assignments because a fourth conductor is needed as the switched hot from one switch module to the light in the middle.
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