Replacing a switch in an old house

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Old 02-27-15, 11:05 AM
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Replacing a switch in an old house

I'm replacing a switch for my home office. The old switch is connected with only two wires - both black unfortunately - and there's no ground and no easily identifiable neutral (ie no white wires). There is a small bundle of three wires behind the old switch (pic below)

The new switch is an Evolve Z-Wave switch, and I believe requires a neutral to operate fully. So I'm just curious what those wires back there might be. Is it possible to have a neutral that's not white? Is there any way for me to test to see if it is a neutral?

Thanks in advance.

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Old 02-27-15, 11:28 AM
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Generally speaking, neutrals are not hooked up to switches so only seeing two black wires does not surprise me. What do you see in the ceiling?
 
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Old 02-27-15, 01:20 PM
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Is it possible to have a neutral that's not white?
Yes, they can be gray but that is almost excursively commercial wiring.

As Stickshift says we need to see the whole circuit including the part at the ceiling. However I suspect you do have white wires but they are cloth covered and have aged to the point they don't look white.
there's no ground
Actually it looks like this is wired with old style BX so you do have a ground though not considered adequate by today's standards. You are grandfathered so any device with a ground should be connected to the box. Not great but adequate usually.
 
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Old 02-27-15, 04:35 PM
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Thanks both for the replies. What am I looking for in the ceiling exactly?

Also, if that bundle is a neutral, does it carry voltage? That bundle does set off my voltage tester. I understand there's a way to use a circuit tester to determine if that is indeed the neutral, but am not clear from instructions how exactly I do that. I was going to take a trip to Home Depot tonight.

When you say any device with a ground should be connected to the box, what do you mean exactly? The current switch does have a green terminal, but it has no ground wire connected.
 
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Old 02-27-15, 05:05 PM
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That bundle does set off my voltage tester.
Not reliable enough to rely on. You need a multimeter, preferably analog not digital. An $8 to $15 one will work fine. We can probably do this without a meter though.
Also, if that bundle is a neutral, does it carry voltage?
Yes.
The current switch does have a green terminal, but it has no ground wire connected.
It should have been.

If this was a switch loop and therefore no neutral there is a 99% there would be only one cable. A sure sign of a neutral is two or more cables and two or more wires connected only to each other. You have that.

A second indication is at the light. If there is only one cable then power comes in at the switch (or far less likely a third junction box.). Those two indicators means almost certainly the two wires you have connected only to each other at the switch are neutral. I would just assume they are.

To test if a wire is neutral you use an extension cord with a ground plugged into a correctly wired receptacle. (A polarized extension cord in a correctly wired receptacle will also work.) You measure between the unknown wire and the narrow slot of the extension cord. If you get ~120v it is neutral. (0v or ~240v indicates it may be a hot.)
 
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Old 02-27-15, 06:18 PM
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You better be really careful moving the conductors to much or you may have more on your hands than you can handle ,those old conductors can have very brittle insulation and can crack very easily.
Just sayin!
Geo
 
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