Home circuit reading 40V all of a sudden?
Mike Reed
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!
RBM
"Mike Reed" <waterr...@gmail.com> wrote in message
news:ddb7d0a2-6875-4389...@g4g2000yqa.googlegroups.com...
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
k...@att.bizzzzzzzzzzzz
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.
Dean Hoffman
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.
Stormin Mormon
power that is transferred by magnetic waves. Your VOM is
probably reading this "ghost voltage". There is probably not
enough amperage to do anything useful. But, your VOM is
very sensetive.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"Mike Reed" <waterr...@gmail.com> wrote in message
news:ddb7d0a2-6875-4389...@g4g2000yqa.googlegroups.com...
mm
<waterr...@gmail.com> wrote:
>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?!?!?!
If you are seeing an induced voltage, you are probably using a digital
meter, which are high impedeance, mabye 11MegOhms per volt.
You mght want to measure the same place with an analog meter. They are
iirc 20KOhms or maybe 50KOhms per volt, either way must lower, so they
put a load on the voltage that dissipates the 40 volts but very low
maximum current that you may have, and the voltage will read
correctly, probalby very near zero.
Analog meters are those with needles that move.
Except for FET-VOMs which are analog and use a needle, but have very
high impedance. I'm not recommending one of those, but I think there
have been none of those for sale for 25 years. And they probably say
FET-VOM on them. At the bottom of the needle area, it says the
impedance of the meter in ohms per volt.
For most things, I still like digital meters, which are auto-polarity
for one thing.
Andrew
> On Sat, 6 Mar 2010 12:47:52 -0800 (PST), Mike Reed
>
I agree with the induced voltage concept. I have encountered this
many times. Put a power strip onto your outlet, then put your
voltmeter into the power strip. If you get 40 V, then plug some
appliance into another receptacle in the power strip. Your voltage
will go to 0. The most likely thing to be wrong here is that your GFI
failed (a common occurrence). You can pull the GFI out of the box and
measure the voltage going to the GFI. If you have proper voltage
entering the GFI, then your GFI is dead. If you don't have voltage,
then your breaker is probably bad. Either is fairly easy to replace.
Mike Reed
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?
Mike Reed
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).
Ralph Mowery
>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?
If you have a very low voltage from the hot to neutral and 124 volts form
the hot to ground, I would look for an open neutral. If you cut the breaker
off and check the resistance between the neutral and ground you may find
that open. There should be a very low (almost zero) resistance between the
two. One guess is there are several recepticals on that circuit and atleast
one is between that one and the breaker box. Try finding all of them and
plugging a lamp into both sockets, one at a time. Chances are you will find
power on one socket and not the other. A jumper between the screws can burn
out between the two.
Roy
==
Get a qualified electrician before you kill yourself. Failing that,
get some code books and read.
==
Ralph Mowery
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.
bud--
Voltages sound like an open neutral, best covered by RBM. I might test
with something like a light bulb in a pigtail socket. If the neutral was
open just H-G would light up.
>
> 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?
Very slight chance a breaker is tripped and has to be turned off hard to
reset.
Do you know which breaker is for that receptacle? (H-G voltage should
disappear when turned off.)
Are any other receptacles dead? (Could be where neutral is open, or also
downstream.)
Do you know of other receptacles on that breaker that are working? (They
would also be candidates for where the neutral is open.)
--
bud--
bud--
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.)
--
bud--
Mike Reed
> "Mike Reed" <waterrock...@gmail.com> wrote in message
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?
Mike Reed
Yep, I've ID'd the breaker, and some of the receptacles on that
circuit are indeed working. I'll roll around and figure out if I can
identify where the open neutral lies.
Mike Reed
> "Mike Reed" <waterrock...@gmail.com> wrote in message
I like the lamp idea. On it.
HerHusband
Start at the source and work your way back.
Remove the breaker panel and measure the voltage right on the breaker
when it's on. If you don't get 110/120 volts there, the breaker is
probably faulty. Replace it before moving on.
If you know the order the outlets are wired in, work your way along the
circuit, testing at each outlet until you reach the end. Most likely you
will read full voltage till you get past a certain outlet. Go back to
the previous outlet, pull it out, and inspect it (with the power off, of
course). I'm betting a connection has arced, come loose, or otherwise
failed in one of the outlets.
If you don't know the wiring order, pull every outlet out one by one and
inspect the wiring. If it were me, I would go ahead and replace every
outlet in the room. Unless it's a very large room or multiple rooms are
on the circuit, it shouldn't cost more than $20 to replace all the
outlets. Cheap peace of mind, and you'll know you have good outlets for
the coming years.
Also, if the outlets are wired "daisy chain" (incoming cable is wired to
one side of the outlet, outgoing cable is wired to the other side), I
recommend rewiring so the cables connect directly with a short pigtail
running to the outlet in that box. That way, power runs directly from one
box to the other, and not through an electrical outlet.
Oh, if any outlets have the spring loaded "stab" connections on the back,
replace the outlet and make the connection on the screw terminals.
Finally, inspect the wiring where it enters and exits the box. I've never
had a problem with plastic boxes, but metal boxes can cut into the cable
or can be damaged if the clamp was overtightened.
Good luck,
Anthony
Mike Reed
So, going from the GFI outlet closest to the breaker (next room), it
was the only one working. I pulled the receptacle from the next one
and examined it. Loose wire in there with some black from a flash/
burn. I tightened it up, restored power, and everything works. I'm
replacing the receptacle right now (same 20A type).
Thanks for the help everyone.
Ralph Mowery
> I like the lamp idea. On it.
>So, going from the GFI outlet closest to the breaker (next room), it
>was the only one working. I pulled the receptacle from the next one
>and examined it. Loose wire in there with some black from a flash/
>burn. I tightened it up, restored power, and everything works. I'm
>replacing the receptacle right now (same 20A type).
>Thanks for the help everyone.
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.
sligoNo...@hotmail.com
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.
--
bud--
Twayne
Mike Reed <waterr...@gmail.com> typed:
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.
--
Regards,
Tom1
--
--
Newsgroups are great places to get assistance.
But always verify important information with
other sources to be certain you have a clear
understanding of it and that it is accurate.
Twayne
RBM <rb...@live.com> typed:
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`
Twayne
k...@att.bizzzzzzzzzzzz <k...@att.bizzzzzzzzzzzz> typed:
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`
-
Twayne
Mike Reed <waterr...@gmail.com> typed:
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.
>
> Strange this all started when I turned on the vac (which
> had worked fine on that circuit since the oven went in).
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
Ralph Mowery <rmower...@earthlink.net> typed:
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`
-
Twayne
Mike Reed <waterr...@gmail.com> typed:
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
bud-- <remove....@isp.com> typed:
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
>
> Unless your area has rather odd practices the electrician
> should not have wired the oven as he did.
I doubt that was done by an electrician; sounds more like a good samaritan
who only obeys code when it makes sense to HIM.
terry
> Innews:ddb7d0a2-6875-4389...@g4g2000yqa.googlegroups.com,
> Mike Reed <waterrock...@gmail.com> typed:
>
> - Show quoted text -
======================================================================
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
>
> - Show quoted text -
Oops. Should hav read the following
first .............................
Quote:
> 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.
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!
k...@att.bizzzzzzzzzzzz
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.
>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.
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.
> First one should always assume and check for it being a phantom voltage
>and nothing more. Jeez!
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
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.
>>
>> Unless your area has rather odd practices the electrician
>> should not have wired the oven as he did.
>
> I doubt that was done by an electrician; sounds more like a good
> samaritan who only obeys code when it makes sense to HIM.
The OP stated it was an electrician.
"A lot more careful"?
When pigs fly.
--
bud--
Ralph Mowery
"bud--" <remove....@isp.com> wrote in message
news:5a1d6$4b967608$cde8d580$24...@DIALUPUSA.NET...
>>> Unless your area has rather odd practices the electrician
>>> should not have wired the oven as he did.
>>
>> I doubt that was done by an electrician; sounds more like a good
>> samaritan who only obeys code when it makes sense to HIM.
>
> The OP stated it was an electrician.
>
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.