Electrical Wiring - Switch Hot Or Neutral?

[master53yoda]

Fellas, it was a simple question, no need to quote code or anything. Oh and to make things even more confusing, I was out there late last night putting some tools away and I looked at it again. I think the way it was actually wired before I redid it was the white from the fixture came in to one switch pole. There was a white jumper from the other switch pole that was wired to black for the incoming hot. The black from the fixture was wired to the neutral.....

I agree 100 % i'm not going there in the thread i'm driving nails

[os1kne]

FWIW, current NEC discourages shared neutrals, but does not prohibit them.

I don't recommend the practice though.

You can still upgrade to 240 V later, though, if you wire each receptacle back to the panel. If you use 12-3, it's easy - just cap the red wire with a wire nut on both ends, connect the black and white for the 120 V usage. When you want to convert to 240 V, change the receptacle and use the black and red wires. Then change the wiring at the breaker to use the black and red on a double pole breaker.

It can be done with 12-2 as well, but you HAVE to color the white wire to make it a black wire to use it as a hot. I usually use a black sharpie. Please completely color the wire - a few black stripes (as I have often seen on installs) can be overlooked by someone working on the circuit in the future.

Thanks for the correction. For my use, I'm going to go with 12-2.

[woodturner]

Thanks for the correction. For my use, I'm going to go with 12-2.

After some private discussion, I have learned a bit more about the original discussion and the reasoning behind the comments, so I want to clarify my response.

NEC does allow shared or common neutral, but there are requirements. A shared neutral circuit is essentially a 240V circuit, so it MUST be connected to a double-pole breaker in the panel. Is is not "legal" to use two 110 VAC breakers for a shared neutral circuit.

Regarding later switching a 110 V circuit to 240 V, I STRONGLY recommend using 12-3 if you want to do this. NEC does allow coloring of the white wire to make it a black to use as a hot, but it's not specficially addressed for applications other than three-way switch wiring.

[woodturner]

And regarding the color of the wiring: it's a convention, and while it certainly is good to wire according to convention, I don't think it's a safe assumption that someone actally did it the right way.

It's a bit more than a convention, wire color is actually specified to an extent by NEC.

I agree that one should not "trust" a prior person to have followed the color code or wired a circuit correctly. Particularly when working with things that can seriously injure or kill me, I find it prudent to check and confirm everything before touching anything.

[woodturner]

There was a white jumper from the other switch pole that was wired to black for the incoming hot.

That sounds like one of the exceptions where the white wire is permitted to carry voltage. Ideally, it should have been painted or taped black to make it clear it is functioning as a "hot".

[crokett]

That sounds like one of the exceptions where the white wire is permitted to carry voltage. Ideally, it should have been painted or taped black to make it clear it is functioning as a "hot".

Yeah, I was taught to tape the white black if it is functioning as a hot but what puzzled me was that before I rewired them the other day, both switches in the box were wired so that a white jumper ran from incoming black hot to the switch, then white went from the other switch pole to the fixture. The black from the fixture connected to the white (neutral) back to the panel. So he wasn't switching the neutral - I was incorrect earlier. He was switching the hot, but he was using the white as a hot. Weird. I suppose it is a good thing that these two switch boxes are the only original wiring I kept. The outlets were all either too low or in the wrong places.

[os1kne]

After some private discussion, I have learned a bit more about the original discussion and the reasoning behind the comments, so I want to clarify my response.

NEC does allow shared or common neutral, but there are requirements. A shared neutral circuit is essentially a 240V circuit, so it MUST be connected to a double-pole breaker in the panel. Is is not "legal" to use two 110 VAC breakers for a shared neutral circuit.

Regarding later switching a 110 V circuit to 240 V, I STRONGLY recommend using 12-3 if you want to do this. NEC does allow coloring of the white wire to make it a black to use as a hot, but it's not specficially addressed for applications other than three-way switch wiring.

Thanks for the clarification. I guess I should clarify as well: Originally, I thought that wiring with 12-3 would accomplish my current need (no pun intended) and "future-proof" me should the need arise for 240V. I've decided to have the first outlet on each 120V circuit be GFCI. There seems to be a strong chance that having a shared neutral on 2 separate 120V circuits could cause GFCI tripping - this combined with the high liklihood that my family will be moving before I have a need for 240V has caused me to decide to keep things simple and just run 2 separate 120V 20A circuits with 12-2. If the need should arise for 240V, I can run it at that time. This seems to me to be the most prudent course of action for my need. Thank you. (I'd probably never use 12-2 for 240V, as the previous owner did this to an outlet in my garage using a standard 120V outlet - it wasn't discovered on inspection and cost me a very nice refrigerator.)

[master53yoda]

I would like to compliment woodturners latest responses as they far better meet the needs of this forum then trivia information does.

Good comments

[gjat]

White is a nuetral, just as green is a ground. For #6 and below, the insulation should have intregal color, phase tape or paint is not allowed. It matters little what 'convention' or 'common practice' is.

Again, I am not a licensed journeyman, though I've spent the last few decades in industrial electric. My opinion is worth what you paid for it (nothing). I'm familiar to what is used in a factory or utility setting, but not what's used in a home or hospital.

My best advice is when it comes to electricity in the house where you, your spouse, and children sleep, it is best to know exactly what you are doing, or hire a licensed professional to do the work or make final connections to double check what you've done. There is lot's of bad information around, like the article with how to wire an outlet we discussed in this thread. When I do stuff around my house, even I ask for a few opinions from electricians. A little extra wire, sized and colored correctly, is well worth it's cost considering what I've personally seen when things go bad. It's one thing for you to personally decide to not wear safety glasses, not using a riving knife, or remove kickback pawls, but if you live on the edge with electrical stuff where others sleep or may have to work with after you sell, you essentially tricked them into dealing with the safety consequences of your choice to save a few bucks.

[woodturner]

There seems to be a strong chance that having a shared neutral on 2 separate 120V circuits could cause GFCI tripping
....
I'd probably never use 12-2 for 240V, as the previous owner did this to an outlet in my garage using a standard 120V outlet - it wasn't discovered on inspection and cost me a very nice refrigerator.)

A GFCI works by comparing the current flow in the hot with the current flow in the neutral. If the current difference exceeds a few milliamps (typically 10 mA), the GFCI trips. In addition, the GFCI monitors current flow in the ground wire and trips if there is current flow in the ground wire (there should never be current flow in the ground wire in a properly operating circuit).

So a GFCI connected to a shared neutral circuit will likely trip frequently, because unless the loads are perfectly balanced there will be current flow in the neutral.

I want to repeat that I am not a fan of shared neutral circuits and do not recommend them. The cost and effort to just run a second NMB 12-2 cable is so minimal I just can't justify the concerns with a shared neutral circuit.

It is NEVER acceptable to use a 120 V receptacle on a 240V circuit. The approved receptacles for 240V are intentionally different so that one cannot plug a 120V device into a 240V receptacle. Unfortunately, not everyone follows code, as you discovered.

For $5 to $10 you can buy a receptacle tester that has lights indicating reversed hot and neutral, ground faults, etc. For $8, this one test for 7 faults and also tests GFCIs:
http://www.homedepot.com/Electrical-...atalogId=10053

When I buy a house, I use a tester like this to check every receptacle - and promptly fix the faults when I close on the house. The home inspector should do this, but many do not.

I also test before working on a circuit. One can never be too careful in working with things that can kill you, in my opinion.

[woodturner]

White is a nuetral, just as green is a ground. For #6 and below, the insulation should have intregal color, phase tape or paint is not allowed.

NEC specifies that white is a neutral in most cases, but can be painted or taped black when used to wire three-way switches. Bare wire and green are specified as ground as you said. However, NEC does allow other colors for particular applications.

The only colors one would normally find in residential AC wiring are:

white - neutral or (if colored black) switched hot for 3-way switches
black - hot
red - hot or switched hot
green - ground
bare - ground

[LarryG]

The only colors one would normally find in residential AC wiring are:

white - neutral or (if colored black) switched hot for 3-way switches
black - hot
red - hot or switched hot
green - ground
bare - ground

All correct but you forgot one other that's quite common in residential wiring: white (colored black) used as a hot in a switch loop for a SPST switch, where the switch is located beyond the light it controls. You'd probably be hard pressed to find a house that didn't have at least one of these, somewhere in its wiring system.

[os1kne]

The cost and effort to just run a second NMB 12-2 cable is so minimal I just can't justify the concerns with a shared neutral circuit.

It is NEVER acceptable to use a 120 V receptacle on a 240V circuit. The approved receptacles for 240V are intentionally different so that one cannot plug a 120V device into a 240V receptacle. Unfortunately, not everyone follows code, as you discovered.

For $5 to $10 you can buy a receptacle tester that has lights indicating reversed hot and neutral, ground faults, etc. For $8, this one test for 7 faults and also tests GFCIs:
http://www.homedepot.com/Electrical-...atalogId=10053

When I buy a house, I use a tester like this to check every receptacle - and promptly fix the faults when I close on the house. The home inspector should do this, but many do not.

I also test before working on a circuit. One can never be too careful in working with things that can kill you, in my opinion.

A big part of my frustration was that I already had a tester similar to your link and a couple of multimeters, etc. - probably 5+ different tools that I could have used to test the outlet, but didn't until it was too late. After that I tested every outlet in the house, and many were not wired properly. (I personally saw the inspector spot-checking outlets, with no mention of any electrical issues in the inspection report). Hindsight is 20/20, so I'll be testing every receptacle on every future home before I buy/move in. Thanks.

[cabinetman]

Hindsight is 20/20, so I'll be testing every receptacle on every future home before I buy/move in. Thanks.

Here's a tester for less than $5, with GFCI diagnosis.
.

[Denn]

switch on neutral ?

Was googling looking for some suggestions, found this site, which has some great posts.

sorry in advance, this is gonna be a rather long post, just don't want to leave anything that might be relivant out.

I recently purchased a forclosure house, build circa 1926. A lot of the wiring has been replaced "by someone before me", but not all. Most of the ceiling lights were removed prior to my purchase of house, with only the fixture box and wires remaining. I understand some of the basics of wiring, have done some in the past, but nothing too complicated. First 3 fixtures I was able to get a new overhead light on without any issues. Just by luck I purchased one of those testers that lights up and beeps whenever it senses electricity, luckily for me, because when I went to the one in the main bedroom, with switch in either position, there was voltage present. There's 2 seperate sets of wires into this paticluar junction box, and I'm sensing voltage on 3 of the 4 wires; read in a previous post with old wiring there can be some false readings with this type of tester. Tried my voltmeter last night "battery is low" so was giving me some weird voltages. will retry tonight with a good battery, but saw voltage on only 2 wires "that much seems about right to me".

I found breaker and turned it off, assuming this was just a neutral switched outlet, having seen one a decade or so ago. I wired an old light fixture "taking off all the extra weight, so I just had the base and 2 wires coming off that" connected this to one set of wires from each of the 2 incoming wires out of the ceiling. nothing. I then connected all 4 wires to the test light, and bingo, I had a light. however all's not good. I noticed that the switch "this one has that little green indicator light" this was lit when the light was on, and was off when the light was off. seems backwards. again thinking this was maybe due to switch being on the netraul instead of the hot.

After a few hours, I shut off the switch, and then turned back on.. breaker tripped "trips on turning off". "Yes I had tested this without any problems right after i got the light to turn on without any trips". after this I could turn on breaker, the light would come on, soon as I turn off light, breaker pops everytime now.

I then dismantled the test light, and looked more closely at the 2 sets of wires. What I had assumed was a white and black set of wires is actually all white cloth, one was just rather dirty, so it's uncertain what should be hot and what should be the neutral. Additionally, after further looking at the 2 sets of wires, I notice that one has 3 cloth bound leads, and the other has 2, plus one wire from each set of wires was already tied together, leaving me 3 wires seperately capped off "as I originally found this".

Rewiring at least the electrical aspect of this would be best, however the house is 90% plaster, this room 100% plaster, and if at all possible would rather fix this that rewire. Ceiling is also the floor of a finished attic, so no good access; rewire, I want to avoid if at all possible. Any suggestions would be greatly appreciated. Going to take one or 2 more stabs at it, before calling in a professional.

thanks in advance.