55 Volts On Both Hot And Neutral, What The Heck!?

karma_carpentry

I just got done reading half of the post called "on discouraging DIY electrical work" and I want to emphasize that I don't plan to work on this problem myself. Plan to call a real electrician. But I discovered the problem myself and it's boggling my mind.

Rewiring a bathroom in a condo in a 3-story 12 unit complex. The old line into the bathroom was a BX cable that came from the bedroom, where it was junctioned from a box for a ceiling fan.

I was going to splice this BX into a 12/2 Romex to get the length to connect into the ceiling fan and wall lights. I tested to see which was the hot, as the insulation jackets were too dirty to see properly (one looked slightly more black and the other one slightly more white). I didn't have a regular line tester with me so I used a multimeter, and I found that each of the conductors were carrying 55V in relation to the ground. There was no hot and no neutral. Across from one conductor to the other wass 110V so they were in opposite phases.

So I was perplexed as heck and turned on the breaker and went to check an outlet in the room with the same circuit. Sure enough, both the hot and neutral slots registered 55V AC in relation to the ground.

I tested an outlet on another circuit in the kitchen, and it was normal - 0V on the neutral and 110V on the hot side.

I went to the subpanel and found incoming neutral and 2 hots, and the 2 hots had a potential of 220V while each was 110V in relation to the neutral, and the neutral was level with the ground. Normal, right?

So, where is the 55V coming from? Don't you need electronics or a transformer to change voltage like that?

I bet M.D. Shunk will have the answer, or at least a good theory.

Please help.

- Stumped DIYer who is calling a pro now but still boggled.

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datafan

I like taking a stab at these before the experts come along and then I see if I was right. It's like answering a question on Jeopardy, so I will put my answer in the form of a question.

Is there something plugged in to this circuit that is feeding through?

K2

I wana take a guess too while the sparkies are at happy hour... What Data said with an open neutral.

mdshunk

Type AC cable (aka - BX) uses the cable armor for the ground path. This isn't always the best ground, and does't get better with time. Recheck your readings by connecting your meter's black lead to a long length of wire connected to a known good ground, perhaps on the ground bar in the panel. I suspect that your measurements will be dramatically different with this testing setup. More like normal.

karma_carpentry

Yes, the ground path is the metallic sheathing of the old BX armored cable. Maybe it's not properly grounded, but then what would it be connected to that could generate a difference of 55V AC to both leads?

I'll connect a length to the subpanel ground and test against that when I'm back there on Tuesday. But still calling a pro electrician.

If the ground is carrying some current in the realm of 55 volts, that sounds like a dangerous bathroom wiring situation.

The GFCI in the bathroom never tripped.

The feed in question comes from the ceiling of the bedroom, where's it's in a junction box with a ceiling fan.

All the receptacles in that whole bedroom have this odd voltage situation as well.

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mdshunk

No, no. The ground is not carrying any current! The ground only carries current under a fault condition.

It is my opinion that the ground is just not connected well at one or several places, hence you don't have a good ground reference path.

You measure 120 between hot and neutral, so they're both good. You just don't have a decent enough ground to reference each one to.

Normally, we'd sort out the hot and neutral with a non contact voltage probe. It's a pen type instrument in which the tip glows when put near the hot wire.

karma_carpentry

So if the ground is just hanging loose, I could still register a 55V AC from each of the leads? Maybe could it be held in the middle of the two leads because of the physical arrangement of the BX cable doing this through electromagnetic field, like a makeshift transformer of a sort?

The same is holding true for all the outlets in the adjoining room, so maybe the whole circuit that is ungrounded.

Guess I should do a continuity test on the ground, back to the subpanel.

Thanks, M.D.!

Edit:

Forgot to add that I did use a noncontact voltage probe to try to figure out the hot lead - that's the first way I tried to do it and because each of the leads set off the probe, I went ahead with the voltage tester from the leads to the ground.

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steveprichard

If you didn't mess with any connections in the bedroom fixture box, then I agree. Test each wire to a better ground or to a known neutral in a receptacle that is nearby. A length of wire works great for this.

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karma_carpentry

Well, I want to report back.

I tested the circuit and it was, indeed, ungrounded.

Called in a pro electrician that I've worked with plenty before, and he said he'd never encountered a 55V reading before, but he confirmed the reading.

My theory is that some part of the circuit has set up a transformer-like effect.

I suspect it's probably in the BX cable. Wherever it is, I think it's putting enough of a current potential into the ground of this circuit that it can register a reading on the voltmeter. Because it's basically a symmetrical physical arrangement -- both the conductors in the same lengths and same number of twists and same position in relation to the ground conductor -- it has the effect of dividing the 110VAC voltage and holding the ground conductor in the middle.

That's my theory. I'd also guess that if I took the hot conductor in one hand and the ground in the other, I'd get a shock I could feel, but too low of a current to really do damage. A 110V stun gun. But I'm not about to try it.

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C&B

just to cover everything make sure all connections are tight in j boxes & panel fixtures etc..

BOB EDMIASTON

check if you have a gfi recept on that circut

BOB EDMIASTON

sorry i seen you do have a ,gfi in the circut. check the voltage on the line side of the gfi then check the load side if it is a feed through gfi .if not take the gfi loose then check the voltage

RobertWilber

Armored cable has a bad tendency to partially fail.
You said you have the old cloth covered conductors in AC cable
What you may find is a combination of ingredients problem.
Bad ground, as suggested, due to poor contact of sheathing and a faulted hot, which is "splitting" the voltage between the hot and the sheath.
I once found this, with the sheath WELDED to an AC duct
That could be why you read half the voltage to the neutral from the hot and from the sheath.
Absolutely run a good clean ground line out as a test lead.
That may remove any confusion
good luck

wildwood

Dude, I'm not trying to be rude but maybe you should leave the electrical theory to electrical engineers. That's like me trying to tell you how the astronauts landed on the moon. Your transformer theory is ridiculous. You mustn't assume "that makes an ass out of you and me" that you are checking to ground. We always check voltage to ground as that is what current takes the path of least resistence to. I gurantee that you don't have 55V at the receptacle. For one, nothing would work when pluged in. I'm not saying that you aren't reading 55v though. I'm also sure that they are still on the same phase and that one is a neutral conductor and one is a hot conductor. Phase to phase would mean no neutral conductor and two hot conductors. You might want to find another Pro to call also. Anyways, I'd love to elaborate more but I'm going to bed. I hope that I'm not out of line and I'm sorry if I am. Peace - ak

fridaymean

If you are getting voltage on the nuetral to the ground, then there must be a broken nuetral somwhere.......if there is a load being applied.

karma_carpentry

Wildwood, dude. I know you said you don't mean to be rude but I still don't like to hear to leave all the theory to the electrical engineers. I'm gonna think about things and be free to discuss them even without an EE degree. I've played with circuits since I was a kid, built electromagnets and DC motors and made things out of coils, capacitors, resistors, etc. If you can tell me why my theory is ridiculous, I'm all ears to it. But all conductors carrying AC current put out an electromagnetic field. Any other conductor in the range of that field will induce some level of voltage. That's how the non-contact voltage detector works, isn't it?

I wasn't assuming that I was testing to the ground - if you read above, I was saying that I think the ground is disconnected on the whole circuit and so it's being pulled in between the hot and the neutral voltages by induction with the physical arrangement of the BX cable.

Also, I said there was 110V from the hot to the neutral, that's why all the appliances worked normally (except they were ungrounded and the homeowner's lucky she never got shocked by any of them).

Hey, I'll think about how rockets work too if I feel like it. I used to shoot off model rockets. I'll work on my truck's emission system. I'm addicted to being a generalist. Maybe it's not the best economically but it keeps it interesting.

But I'm committed to not stepping on professionals' toes. Like I said above, this is a theoretical discussion because we called the professional electricians. By the way, he ran a cable to the panel and tested the ground, verified the circuit is ungrounded. He ran a new feed to the panel for the circuit and a dedicated feed for the bathroom which is now on its own circuit.

RobertWilber - thanks for the suggestions - I don't know what you mean by the faulted hot...

wildwood

Mr Karma, You sound like a good guy and I'm sorry if I came off the wrong way last night. I give you a lot of credit for being a "thinker". After reading your response, you actually sound fairly intelligent. Please accept my apologies and remember that I don't know everything either. Gotta go make some money. Have a good day. ak

RobertWilber

A fault is an "unintentional" path of a conductor to ground.\
Since this circuit in "ungrounded" it is probable that the hot feed is touching some item that would otherwise be at ground potential.
Many other possibilities....just first idea,
Digitial or analog meter? [digitals often manifest "ghost"

karma_carpentry

Wildwood, thanks man. I appreciate the strength of character to apologize. It's no big thing anyway and maybe I am totally wrong, who knows? Until take a 10 foot scrap of BX and hook it up the hot and neutral to 110V and perform the same test in controlled conditions. I guess that experiment would give the answer.

RobertWilber, thanks for explaining what you mean. I don't think the hot is contacting the ground anywhere bcs then I'd expect 'shocking' conditions and to get 110V to neutral and 0V to hot leads, not 55V to each.

I used an analog meter but the electrician confirmed it with his digital meter. What I never measured was current, only voltage.

Hey, if I get a scrap of BX I'll run the experiment and let y'all know the results then you'll know what it may or may not be if you ever see 55V in the field.

macmikeman

Usually an extension cord plugged into another outlet, preferably a kitchen outlet will get you a good ground to test with. Probably this will be an easy(ier)? safer way for a carpenter to get a reading than to have to open up the panel and hookup to the ground bus. Test for your readings between the outlet and the ground hole on the extension cord. Please do not try to do any "test rigs". That can lead to injury or death. Call in that electrician you mentioned.