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I get shock when I touch Grounding (earthing) wire

by vbitla
Tags: earthing, grounding, shock, touch, wire
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vbitla
#1
Jul6-12, 09:11 AM
P: 2
Hello experts.

This is a unusual behaviour. I moved to new house, an apartment newly constructed less than a year old. I first noticed shock when I was disammbling my computer , i immediately took out multimeter and tester.

First checked with tester, it did not show any symptoms of grounding not present.
Checked the potential difference between Phase and Neutral (230V) which was according to standard, then between Phase and Ground same 230V and ground and neutral (zero Volts).

Intresting part when I check the potential between me and grounding wire (earthing) multimeter reads 32V.

I checked with the owner of building and he says earthing was done properly. I checked every socked in my house and gives same result.

What could be the problem and how can I rectify?
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psparky
#2
Jul6-12, 09:25 AM
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If it were me...the first thing I would do is look inside the electric panel and make sure the ground wire was securely fastened......don't think I would touch it though since there may be something shady going on.

Then I would trace the wire outside and make sure it was actually grounded into Earth.

Sounds like you may have some sort of floating ground....or perhaps you are the first 32 volt human being on Earth.

Might be some sort of short goin on as well......
vbitla
#3
Jul6-12, 09:39 AM
P: 2
I cannot check the electric panel.
wire outside is grounded into earth, i am assured.
I am not a 32 volt human being, because i am not the only person (everybody in my family get same results).

If earthing wire is not grouned , then there should be a 230v potential difference between me and grounding.

Any other?

AlephZero
#4
Jul6-12, 11:35 AM
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I get shock when I touch Grounding (earthing) wire

Quote Quote by vbitla View Post
I checked with the owner of building and he says earthing was done properly. I checked every socked in my house and gives same result.
Is the owner a qualified electrician? If not, how does he doesn't know it is done properly?
What could be the problem and how can I rectify?
Try to check if this is really a problem with the house wiring, or with something you have. Unplug everything from the mains and see if that fixes the problem. If that does fix it, plug things in one at a time till you find the cause.

If unplugging everything doesn't fix it, I would try to get somebody qualified to check the wiring. A 32V shock probably won't kill you, but if the cause of the fault gets worse you might get a 230V shock one day.

Depending on the laws in your country, the owner should be responsible for the cost of fixing it, and you could probably take legal action against him if he refuses to fix it.
psparky
#5
Jul6-12, 11:43 AM
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Quote Quote by AlephZero View Post
Is the owner a qualified electrician? If not, how does he doesn't know it is done properly?
I totally agree with this....and the other stuff Alephzero said as well.

You simply can't assume anything. If everything was working properly....you wouldn't be getting 32 volts. There is clearly a problem and it may be with the grounding that has been "assured" to be installed correctly.

Also....if this is a rental....it is your landlord's responsibility to hire a qualifed electrician to rectify the problem. Without inspection of your electric panel....you have nothing in my opinion.
jim hardy
#6
Jul6-12, 03:11 PM
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Anecdote - but i think it's relevant

a friend who's in airconditioning business once asked me how to check grounding on an outdoor unit. He had a rooftop unit that was corroding severely, eating the aluminum fins off the condenser coils. Incoming 230V looked fine by voltmeter.

He located the earthing wire at point where power came into the building on ground level. The he got a lomg enough enough wire to reach from rooftop A/C unit to that earthing wire and sure enough , frame of unit was ~ 20 VAC wrt incoming earthing wire.
That encircled the problem to wiring inside the building which he, like you, couldn't access. But the electricians immediately recognized it as a serious safety issue and corrected it.
He reported a year later that the new condenser coil was not corroding after fixing the ground. I still dont know what they found.

sorry for the old-timer's tale.

Point being - if you find where power comes into your building you should find a large bare copper wire going into the earth very close by. If there's thirty volts between that and the ground prongs of your wall sockets, there's a problem in building wiring.
Can you borrow a long length of wire?
triden
#7
Jul6-12, 05:44 PM
P: 173
The 32 volts you measure could be a phantom voltage on the line. This happens a lot in household AC circuits when you use a high impedance volt meter. Electricians have special probes with a load resistance in them to get rid of any phantom voltage. Ive personally seen phantom voltages over 60 volts on "open" 3-way circuits.

If you are getting a shock, hopefully it is just a static build up. A 32volt source will not shock you in most cases as it is not large enough potential to get much current flowing through the body.
sophiecentaur
#8
Jul7-12, 08:01 AM
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Quote Quote by triden View Post
The 32 volts you measure could be a phantom voltage on the line. This happens a lot in household AC circuits when you use a high impedance volt meter. Electricians have special probes with a load resistance in them to get rid of any phantom voltage. Ive personally seen phantom voltages over 60 volts on "open" 3-way circuits.

If you are getting a shock, hopefully it is just a static build up. A 32volt source will not shock you in most cases as it is not large enough potential to get much current flowing through the body.
It's not likely to be "static". If it happens when you touch it twice within seconds then it is not static. You could be suffering from two simultaneous faults: firstly a poor earth and, secondly some leakage through some poor insulation. If you connect a sensitive multimeter (AC micro amp setting) between the offending equipment and a water pipe (which should be Earthy) you may measure a small current. Try this with various pieces of equipment turned off and see if it goes away. Water heaters / kettles are very bad in this way.

But basically, I think it's your landlord's responsibility. Get him in to 'feel' the effect and prove that you have a reasonable worry.
Dickfore
#9
Jul7-12, 08:53 AM
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So, you get 230 V between both phase and null, and phase and ground, 0 V between ground and null. But, you get 32 V between you and ground.

Is your multimeter on the AC setting?
TurtleMeister
#10
Jul7-12, 09:18 AM
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Are you getting shocked every time you touch the earth ground, or was it the one time when you were dismantling your computer? If it was just the one time, then it could have been due to static discharge. As triden pointed out, the reading you are getting on your meter could be due to capacitive coupling between your body and the building wiring. Modern multimeters are very sensitive because they have a high impedance input. Try using a cheap 1000 ohms per volt meter, or just connect a 1 megaohm resistor between the probe leads. This should make the reading go to zero. However, if you get a shock every time you touch ground, then there is a problem.
psparky
#11
Jul7-12, 11:53 AM
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Quote Quote by Dickfore View Post
So, you get 230 V between both phase and null, and phase and ground, 0 V between ground and null. But, you get 32 V between you and ground.

Is your multimeter on the AC setting?
If he's getting 230 volts it would have to be on AC. If he was on DC....he would be getting 0 volts phase to phase or neutral or however you guys do it in the UK. Correct?
Dickfore
#12
Jul7-12, 11:56 AM
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Quote Quote by psparky View Post
If he's getting 230 volts it would have to be on AC. If he was on DC....he would be getting 0 volts phase to phase or neutral or however you guys do it in the UK. Correct?
Well, digital multimeters have built-in rectifiers, filters, etc., so measuring AC voltage on the DC setting is bound to not give you a correct reading. I was just asking to confirm.
FOIWATER
#13
Jul7-12, 03:53 PM
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ive actually seen phantom voltage happen so frequently i would bet money that's what it is.

I also agree that you are not likely to get shock from the measured 32 volts.

I have read upwards of 20 volts from me to my toolbox at work.

Although I can't be sure.

You could have a hot wire that is slightly grounded, but 32 volts to ground is enough to trip your breaker (i know its not Necessarily true, but talking about what's most likely, It is your houses grounding condition).

My old house was the same way, we had carpet, and you couldn't touch a light switch without a massive static discharge

IN fact, if you scuffed your feet across the canvas in the kitchen, and put your hand under the already running water, you would get a large shock as well.
the_emi_guy
#14
Jul9-12, 01:51 AM
P: 585
Quote Quote by vbitla View Post
Hello experts.

This is a unusual behaviour. I moved to new house, an apartment newly constructed less than a year old. I first noticed shock when I was disammbling my computer ...

The OP needs to tell us two things:
1 - exactly what was he touching (both hands) when he experienced this shock.
2 - What did this shock feel like. Tingling?

Regulatory limits for touch current through AC adapters in class 2 equipment such as laptops is 250uA (EN60950). This is not harmful, but produces a very noticeable tingling sensation. Medical equipment designed to be attached to the human body have significantly lower limits for touch current so that there is no physical sensation.

Several years ago Dell computer had a lot of customers complaining about shock while using their laptops with brushed aluminum finish and two prong adapter despite the fact that the adapter was compliant with touch current limits.


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