How to test for a neutral line in a switch box?

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wrote:

This only works if you haven't separated the wires yet. If you have, there may indeed be voltage on the neutral. WATCH OUT!
BTW, what are you doing poking around in a box with the power on? ;-)
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snipped-for-privacy@attt.bizz wrote:

Hi, If it is simple switch box with wires only for that it may be simple to sort out which is which but crowded box with other wires pass through or doing some thing else it may take a while to figure that all out. Our one bathroom has 3 ganged boxes full of wires doing several things, Jacuzzi pump timer, IR heat lamp/vent fan, light fixtures..
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wrote:

Sure, you can often visually determine which wire is which but *measuring* voltages implies that you're disconnecting wires (at least removing the wirenuts). Not smart, without disconnecting power.
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wrote:

In which case there WILL be a neutral in the box which could be pressed into service, although if that neutral is associated with a circuit on a different breaker or fuse it is technically illegal to use.
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On 12/14/2013 12:13 PM, snipped-for-privacy@snyder.on.ca wrote:

And if you have GFCIs or AFCIs will cause them to trip, if the current through the devices is greater than 5 mA (GFCI) or 30 mA (AFCI)
nate
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On Fri, 13 Dec 2013 01:40:16 -0500, snipped-for-privacy@aol.com wrote:

More specifically, there should be *ONE CABLE* that has a black, white, and bare (there will be more than one). In that one cable, one that's not connected to a switch will likely be the neutral. Those that are connected to mechanical switches should be marked clearly as something other than neutrals (colored tape or marker) but electricians are often sloppy.
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On Friday, December 13, 2013 1:31:04 AM UTC-5, Jennifer Murphy wrote:

I'm trying to understand - you're saying that the hot wire was run to the switch, but not the neutral? So the switch box only has one wire in it? Why would anyone do that?
Most hot wires in a switch box should be black (with some exceptions); neutrals always white, and the ground either bare or green.
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On 12/13/2013 08:42 AM, TimR wrote:

Could easily be a "switch leg" where the feed cable goes directly to the switch box and then a 2 wire plus ground cable is dropped to the switch box. The white in the switch leg should be marked with black or red tape to indicate that it is not being used as a neutral. Perfectly code compliant up until the latest revision.
To provide a neutral in this situation the switch leg would have to be repulled with 3 wire plus ground cable. Also boxes should be re-evaluated for box fill, one or both may need to be replaced with deep boxes.
nate
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On Friday, December 13, 2013 8:42:13 AM UTC-5, TimR wrote:

Noi, the switch would have both a hot wire and the wire going to the light/load connected to it. The neutral would never be connected to the switch. Most times, around here at least, the way the wiring is run, the box has a neutral in it anyway. But until very recently, there was no code reqt to have a neutral in the switch location.

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Lazy electricians and cost cutting measures. The difference between sourcing or sinking a load. These can confuse a novice. Proper application would be that the neutral should pass through the j-box the switch is located in with the hot being switched before continuing on to the switched device. Preferable should be a more "proper" term, I suppose.
Usually the black tape on white wire is to denote a switched hot that is used in the feed of a 3-way were both conductors in the romex are hots. For a normal switch this is not necessary.
I realize this is not a perfect world and many will cut whatever corner that is allowed to facilitate a "legal" installation however funky this may be. Most times the dollar wins out over intuitive installation. People forget that what the code states is "what is allowed", not what is preferred or is better.
Many only care about the "it passed" nature of the trade, not the quality and down the road maintenance of the installation.
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On Friday, 13 December 2013 13:00:18 UTC-5, Irreverent Maximus wrote:

Why exactly are switch legs un-preferable?
Chip C Toronto
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On 12/13/2013 03:58 PM, Chip C wrote:

A lot of line-powered switches require it.
For example, my Insteon switch modules require a tiny amount of power to listen for remote commands.
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On 12/13/2013 12:31 AM, Jennifer Murphy wrote:

All you have to do is look in the junction box.
There should be one green or bare wire going from the junction box to the metal mounting tab of your switch. That is the /ground/ and though it is not energized /cannot/ be used as neutral.
Next, there will be one wire going to each terminal of the switch.
If there is a white wire in the junction box that is taped off...or perhaps runs to some other circuit...then that is your neutral wire. If there are no other wires in the box (or wires that are anything other than white) then there is /no/ neutral.
NOTE: If one of the wires connected to the switch is white...it is /not/ a neutral but simply the wire going to the bulb. It may have a piece of tape on it with a color other than white.
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It indicates it is a "live" conductor - not a neutral as white would indicate.
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Jennifer-
The wire coming from your fuse/breaker box to the switch box is the "Line". The wire that goes from the switch box to what is being switched, is the "Load" wire.
Now go to the load being switched. One wire is the "Load" wire from the switch. The other wire is the Neutral line you need.
I think your best alternative would be to re-route the existing Neutral line through the switch box. Otherwise you may need to run a new Neutral wire from the fuse/breaker box to the programmable switch, and on to the load.
Perhaps your electrician can advise you.
Fred
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Fred McKenzie formulated the question :

Perhaps is a very gentle word. If someone with absoutly no understanding of electricity had got an electrician in the firt place we could have saved this whole thread and avoided a lot of rubbish from the semi literate.
--
John G

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wrote:

If the house is wired with "romex" you cannot "add" a neutral - it needs to be totally rewired to get a neutral.
Basically there are two ways of wiring a switched load, like a light. You can switch the power TO the load - running the cable (line and neutral) from the panel to the switch, and from the switch to the load, with the neutral wire-nutted together, or you can switch the power "from" the load - running the cable from the panel to the load, and the load to the switch, wire-nutting the neutral together at the light - and running a cable down to the switch where both black and white wire can be "live".
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