Home circuit reading 40V all of a sudden?

[Ralph Mowery]

Glad you found it,

Simple wasn't it ?

I am an electrician at a large plant, but I did not stay at a Holiday Inn.

I had something similar like that happen to me about 15 years ago. It took out the hot wire instead of the neutral. Vacuum cleaner did that to me also. Guess that motor starting up draws lots of current and will take out any marginal receptacle.

As far as the wiring question with the stove, I would not like to guess at that without seeing it. I don't think you will have any problems with it, but still do not like the idea of borrowing a ground with a wire of a much lesser gauge than the main wires. I don't know the code for the grounding, but bet it would not pass. As mentioned the old 3 wiring should be grandfathered in and would be ok. Most stoves will use the two 240 volt wires for the elements and very little current will be on the neutral wire, just whatever the stove uses for the 120 volts. Probably only the lights and clock/oven control circuits.

[sligoNoSPAMjoe]

I would suggest two things. You have a bad neutral. Very bad and very dangerous, or you are using a sensitive digital meter that is picking up ghost voltage. As soon as you put a load on that kind of circuit, it will dorp to zero volts again. The first one you call the pro in. It might be in your home or it might be a problem out side.

If it is the second issue, it is nothing of substance.

[DD_BobK]

..

Mike-

When you replace the receptacle, wire it up using the pigtail method.

The black from the "supply" and the black to downstream loads should be wire nutted together along with a short (pigtail) black wire that supplies the local receptacle. Do the same with the neutrals.

Wiring up a receptacle in this manner will keep the rest of the circuit working even if a "local" device fails.

cheers Bob

[bud--]

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.

[Twayne]

What you have is an open circuit in the Hot lead somewhere back to the breaker box, almost certain. The 40 Vac will often be a simply "phantom volage" caused by all kinds of things in the air and the high impedance of the meter can see it. Plug a nightlight or anything with a bulb into the ckt and the voltage will almost surely go away. It's sort of like static voltage, but comes from a different source by way of an analogy. 40Vac is a rather typical voltage for such things. If the 40V ac does not go away when a bulb is plugged in, there there is a serious wiring problem somewhere but 99.999% of the time it's going to be an open ckt in the wiring. Probably at an outlet or a switch. In fact, even properly wired ckts will often show the 40Vac if there is a switch to the outlet and it's turned off; same situation an an open ckt. But when the switch goes on, it should jump to a solid 120Vac level, whatever voltage is normal for your area.

It's may or may not be dangerous; it depends on where and how the open ckt has occurred. You should get it checked out soon, or open that breaker until someone does get there to look at it.

[Twayne]

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.

HTH,

Twayne`

[Twayne]

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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[Twayne]

I don't understand your description, but it's far from meeting code so you really do have something to be looked into. I still think you have an open ckt somewhere, either hot or neutral, depending on where you're seeing the

40Vac measurement. If one shows the 40V and not the other, that's going to be the one that is open ckted. Remember though if it's a switched outlet, the switch must be ON for the ac measurement. Another way to check the wires is to ohm them out. Kill the main power breakers and open the relevant breaker. and tie the hot to the neutral at one end or the other, and measure the ohms of the wires from the other end. It shouldn't be more than an ohm or two, often closer to a half ohm or so. Don't forget to disconnect hot from neutral when you're done. 120Vac hot to gnd = OK 0.0V neutral to gnd = OK assuming there IS a gnd wire connected. 120 Vac hot to neutral = OK.

Radio Shack sells handly little testers you just plug in and read the LEDs for this kind of thing too; handy to have.

Sounds like the vac just tripped whatever had to happen to push the ckt to an open ckt. Not unusual for loose wires in a fixture/outlet/switch/etc. They start with a surge that would create an arc if there were a poor connection and eventually the carbon from the arc would open the ckt. Happens all the time with loose connections.

HTH,

Twayne`

[Twayne]

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:

of info online if one looks.

HTH,

Twayne`

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[Twayne]

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`

[Twayne]

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.

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`

[terry]

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This business of false or phantom voltage readings has been mentioned many, many times on this and other news groups in the past.

Even the cheapest of today's digital multimeters can pick up induced voltages from a 'dead' or disconnected wire which runs nearby other wires etc. A reading of 40 volts is probably meaningless. Another meter might give 21 volts; again meaningless! And even radio/wireless waves, which are very low strength higher frequency AC emanations can be picked up by any length of wire acting as an antenna/aerial!

As variuos posters have mentioned 'plug something 'real' such as a lamp, into the GFI and if it does not light up something is open somwhere between the output prong contacts of that outlet and circuit breaker feeding that circuit. Try the preceding outlet on that circuit to see if it it has power!

If all is correct back to the circuit breaker there should be full

115/120 volts on the live lead (usually black*) lead into the 'input' side of the GFI. However the neutral (usually white*) could be open. *In North American practice.

Finally the GFI may be faulty. Pertinent ...................

Question; are any outlets 'upstream' of the GFI working OK?

Question; is the GFI the last outlet on that circuit 'run', that would mean there are no further outlets downstream of it!

Question; or is the GFI the first outlet on that circuit run; if so and it is faulty then all other outlets downstream of it may also have no voltage.

It is also very difficult explaining when one has no idea of the electrical knowledge of the enquirer! Something that, makes complete sense to anyone knowledgeable, may be difficult/dangerous to someone not so.

[terry]

,

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Oops. Should hav read the following first .............................

Quote:

Unsafe by my reckoning, double ovens hooked to what gauge wiring?????? "using the oven's ground for the neutral ..............." yikes!!!! More than hokey by sound of it. And don't think an insurance company would be very sympathetic if something did happen!

[krw]

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.

[bud--]

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

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.

[Ralph Mowery]

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.