Home circuit reading 40V all of a sudden?

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Hi,
I plugged our vacuum in to the GFI in the kitchen, and when I turned it on, I heard a "pop" and assumed it was the GFI that needed to be reset for some reason. Well, the GFI plug was acting completely dead.
I pulled it out of the wall, pulled off the line wires and tested them bare.
40V?!?!?!
This circuit was fine this morning and has been installed for years. We recently remodeled and moved a couple plugs around, but they've been working fine for months (all on the GFI).
The breaker goes both directions with a positive click just like the rest. This all started with the vac switch. I turned around and used the vac on a different circuit with no problem.
Any chance someone's seen this before?
Thanks!
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On Sat, 6 Mar 2010 12:47:52 -0800 (PST), Mike Reed

I bet you only paid 40% of your electric bill this month !!!!!
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The circuit to that outlet is most likely coming from another nearby kitchen outlet. Either it was wired through the "load" of the other outlets ground fault protection, or you have a loose connection at the location prior to the one with the dead outlet. The 40 volt reading means nothing
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In

Well, the open will be somewhere between that line and the breaker/fuse box, not just at the adjacent fixture. The 40V reading is very likely just a phantom voltage. http://en.wikipedia.org/wiki/Phantom_voltage
HTH,
Twayne`
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wrote:

Plug a lamp into the outlet when you read the meter. If it really is 40V the neutral on your house has likely opened. The other leg of the 240V service will have 200V on it! This is obviously a very dangerous situation. Get it fixed FAST. Shut everything off in the meantime.
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In wrote:

That's a kneejerk reaction. An open neutral on the "house" would affect everything in the house, not just that ckt, and the vac wouldn't have run on another ckt. As for 200V I assume you're thinking 120 + 120 = 240 but it doesn't work that way unless the EARTH GND were missing, in which case there would be many other symptoms, but none very dangerous or requiring shutting off anything but the relevant breaker. Under no current circumstances, 120 of opposing ac polarities, guess what it equals in between them? Somewhere between 0 and usually 120Vac. First one should always assume and check for it being a phantom voltage and nothing more. Jeez!
HTH,
Twayne` -
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I described, in the paragraph you quoted, how to figure out if it was a real reading and whether it was an open neutral. If it was, I said to fix it fast. Please read.

Wrong. *EXACTLY* that will happen if you lose the neutral connection off the house. The 240V will divide somehow, and depending on the load on either side, it could easily be 200/40. BTDT.

Before attempting to correct those who really know something about electricity[*], with your twaddle, READ. Jeez!
[*] BTW, I am an EE.
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Mike Reed wrote:

Check from the neutral wire at the outlet to the equipment ground. You should have near zero volts there. If not, the neutral is probably opened as someone else mentioned. The breaker might be bad even if it switches off and on like normal.
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Thanks to everyone for the comments.
Ok, I pulled out the receptacle and disconnected the line wires to test them the hot/neutral voltage is ~11V, probably the close-wire effect (mentioned elswhere) there.
Neutral/ground is zero, and hot/ground is 124V, just like working receptacles. So now I guess I check to see if the breaker is bad? Obviously the breaker box poles would be ok since all the other circuits on that side are working fine, right?
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Well, I guess it can't be a bad breaker if the hot is hot working...
So I have an open neutral probably?
I'm starting to suspect a modification made about two montsh ago to accommodate our new double ovens. We had 240 going into the box for the oven, with one hot 240. The new oven required a 4-wire connection with two 120V hots. The electrician used the oven circuit's ground for the neutral, the neutral for the 2nd 120, and borrowed ground from an adjacent 120V GFI receptacle. I think something's hokey with that arrangement or its implementation.
Strange this all started when I turned on the vac (which had worked fine on that circuit since the oven went in).
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== Get a qualified electrician before you kill yourself. Failing that, get some code books and read. ==
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wrote:

The new oven could have been wired the same as the old one. Just use 3 wires. While it will work ok electrically, the 'borrowed' ground wire may not be heavy enough to carry a short circuit current, especially if the short is not a 100% short, but a low to medium resistance short. That could result in the 'borrowed' ground wire getting too hot over a long period of time. Probably the borrowed ground wire is 14 gauge and the wires going to the stove are much larger.
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Ralph Mowery wrote:

I agree. Some range circuits used to be just hot-hot-neutral and the neutral was also used for the ground. New circuits need a ground, but the old connections are still explicitly grandfathered in the code. Picking up the ground elsewhere is not appropriate (and is a code violation). Also at least one wire size too small.
I doubt it is the direct cause of the problem now. (But digging around in the box may have loosened a different connection.)
--
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The ground is borrowed from a 14g cluster (same nut), but is a much larger stranded wire going to the oven box. The ground that was converted to neutral is much larger than 14g and stranded as well. So this should be ok then?
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Mike Reed wrote:

The conductor in the oven supply circuit should be a neutral (not ground). The main question is the size of the ground wire from the kitchen receptacle to the panel. It is also not appropriate (and is a code violation) to run the ground through another circuit.
If it was my house I would remove the ground wire to the kitchen receptacles and use the supply neutral as the oven neutral and ground (NEC 350.140-exception). Finding installation instructions for the oven would be a good idea (hopefully would cover a supply circuit with a neutral and no ground). There may have been a bonding clip at the oven. Connecting it right is a safety issue - if you are not clear how to reconnect the oven it is better as is. Might be worth a call to the electrical inspector for advice on what to do.
Unless your area has rather odd practices the electrician should not have wired the oven as he did.
--
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In wrote: Well, I guess it

Actually, since a stove is going to have exposed metal, the ground connection is going to be the required connection. If it has a clock or anything else that runs on 120Vac, then a 4th wire, Neutral must be added to the mix. A pure 240Vac ckt does not require Neutral to operate. This looks like a good explanation of it all: if one is missing, it's going to be the Neutral, not the ground. http://www.nojolt.com/basic-220-circuits.shtml

I doubt that was done by an electrician; sounds more like a good samaritan who only obeys code when it makes sense to HIM.
HTH,
Twayne`
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Twayne wrote:

A mere 2 months ago you told HeyBub "next time I'll be a lot more careful." Obviously not.
From world war 2 until the 1996 NEC, oven (and dryer) circuits were allowed to be run in a H-H-N cable (with restrictions) and the oven/dryer ground connection was allowed to be made to the supply neutral.
Since the 1996 NEC the continued use of these circuits has been "grandfathered", as I previously wrote. If you were "careful" you could have read the citation I provided - NEC 350.140-exception. Many people here know all this, including Ralph Mowery. But you have to spread your ignorance.
If you read *your* source in another of your posts http://repair2000.com/cord.html you would see a 3-wire dryer connection where the neutral wire is connected to the dryer ground by a "bonding clip" I referred to in my post above.
And in a different post you said "What you have is an open circuit in the Hot lead somewhere...." You posted this not only after the OP provided voltage readings that indicated the open was in the neutral, but after the OP stated that he found the problem and it was an open neutral.

The OP stated it was an electrician.
"A lot more careful"? When pigs fly.
--
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While it was stated an electrician did the work , if it was done by atleast one electrician I know, the work could be very substandard. I would not let this guy change the battery in a one cell flashlight. Sounds like the OP may have hired someone like this.
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In wrote: Well, I guess it can't

No. Ground and Neutral can NEVER be connected together anywhere but back at the breaker box! You have to work to code since you're doing it now, not back in the days of Edison; soon's you touch it, grandathering is out the window for that part of the ckt, if it ever was actually grandfathered, which I'm not so sure of.
HTH,
Twayne`
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In wrote:

That setup sounds fishy; not to code and not smart to have, IMO. Needs to be checked out by someone with experience IMO, preferably licensed electrician. In a N.A. 240Vac ckt, there should be NO current in the Neutral; it's all in the two 120 lines. The earth of course needs to always be there with a 4-wire connected stove. A "borrowed" ground isn't right any way you look at it, assuming it means earth ground. They should never be of different breakers until they get all the way back to the breaker box. This is for dryers, but it might help understand things: http://repair2000.com/cord.html Lots of info online if one looks.
HTH,
Twayne` -
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