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shock from Ground (green) wire.

Posted by davidro1 (My Page) on
Wed, Mar 31, 10 at 12:07

I got a shock when the ground wire got disconnected.
What should I be looking for as a fix / diagnosis ?
I turned the circuit off.
There is no voltage on the ground wire now.

It's a 220V induction cooktop.


Follow-Up Postings:

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RE: shock from Ground (green) wire.

This is a little unclear.
Did you get a shock from the grounding conductor, or from the appliance? Why did the grounding wire get disconnected?


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RE: shock from Ground (green) wire.

The wire got disconnected because the wire nut didn't hold well.
The nut holds a single hard copper grounding wire to a thick twisted copper cable.
The nut was loosened when the sheathing around all three wires was moved around.
I will clamp it!

The appliance was not on at the time.
The shock was from the appliance.
It could be a leakage current, and normal, but I'm unsure how to proceed.


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RE: shock from Ground (green) wire.

Are the green wires and the white wires connected to the same bus bar in the circuit panel? You MAY have a short in the oven that will trace back to the green. Or some circiut is on in the rest of the house.


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RE: shock from Ground (green) wire.

Is the cook top a 240 V load or a 120/240 V load?

Is the unit contain instructions for 3-wire and 4-wire installation?


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RE: shock from Ground (green) wire.

Another posting that fell into the thread abyss.
Hope the guy didn't get electrocuted.
davidro1 - if you're still alive, I'd say it is more likely that you have an appliance problem than a house wiring problem. Recommend you call an appliance repair person.
"Leakage current" is NOT normal, nor is getting zapped by your cooktop.


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RE: shock from Ground (green) wire.

I bet this is a 120/240v appliance where someone used the bare ground of a X/2NM cable as a neutral in a 3-wire installation.

As to the thread, it helps if an original poster comes back to give more info when more info is needed.
After the first day the OP disappeared.


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RE: shock from Ground (green) wire.

It's a 240 V cooktop.
It's still under warranty.

There are only two wires (two hots), and a ground wire.
(Does this mean the white (neutral) remains un-connected? -- Y / N ? )

In the manual, it says to "follow the connection schematic" but there was no schematic diagram in the box.

I sent this to the company:
"While preparing for the countertops to be installed, I moved the cooktop to an adjacent cabinet, and did not disconnect it. In so doing, the cooktop's ground wire (green) got disconnected accidentally (wire nut loosened), and I received an electric shock, more than once before I found the cooktop's thick green cable loose from the building's romex single-strand ground wire (also green).
"The cooktop had not been turned on while I was looking at it to determine the problem. I'm wondering how an appliance not in operation can leak that much current through its ground wire. Now, looking into the manual, I realize there is no information about the wiring or schematic diagram.
"Do you know if there is a schematic? It might be simple, providing no new information, but it's good to look at nonetheless.

So, I'm telling them about the shock(s) but asking to see a schematic first, before I start getting the warranty involved.

The fact that there was more than one zap is the thing that is making me look into this a lot.
Those who know more about these things can tell me if it is normal for a ground connection to be the route for excess charge to be released, -- AND more than once -- while the device is not ON and also has not been turned on between the intermittent shocks.

At first I thought it was a capacitor discharging, but when i got another "intermittent" shock I really started thinking there may be something more to it. Of course I don't feel like testing for more intermittent shocks with my hands on loose ground wires... (!) or waiting around with a multimeter hoping to see the needle jump.. . : - )


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RE: shock from Ground (green) wire.

"tell me if it is normal for a ground connection to be the route for excess charge to be released"

No.
And there should not be any real build up of static on a stationary appliance.

The schematic may be located on the back/bottom of the unit, or even in the wiring compartment on the inside of the cover or inside the unit.


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RE: shock from Ground (green) wire.

Hello again.
Below is the letter I'm ready to send to the company that handles warranty.
Please feel free to comment !!

---
X,
I think there is something worth sharing here.
It's a bit too much for a phoned-in description so I am not eager to make a phone call as the first point of contact.
Perhaps __(the manufacturer)__ needs to see the "Interesting part" below.

Yesterday I received a voicemail message call from someone in your firm asking me to call back to speak to you.
I'm glad someone called.
He said he had seen the email sent yesterday.
He made a small mistake in his description of the situation.
This is one good reason to write things down.
Please read.

I have the __XxxX_ cooktop.
It's still under warranty.
I found a small visual "schematic" on the underside of the cooktop.
It mentions different color wires than the red, black and green wires which the cooktop has.
I'll guess the wires were replaced by you or by the factory so as to correspond to North American standard colors.
If so, it changes nothing electrically.
It has two wires (two hots), and a ground wire.
The black and red take the two hot wires of a 230V circuit, and the green is grounded.
If this is correct, read on; otherwise please advise.

In the manual, there is no information about the wiring or schematic diagram.
In the manual, it says to "follow the connection schematic" but there was no schematic diagram provided, separately, and none in the manual.
If the visual provided in the label on the underside is the schematic, this would be good to know.

Good news: the cooktop works.
I've been using it every day for a few weeks now.
I'm not sure if it works perfectly as expected, because sometimes I get a dash result (-) on the display and that burner turns off.
This is when I put high heat on a large cast-iron pan at a burner at the back; these are medium sized burners.
Later, when I give away the cast iron and get stainless induction-ready pans I expect this problem to disappear.
Other than that, it appears to work fine.

Bad news: it gave a lot of medium-voltage shocks when ground got disconnected.
Last week while preparing for the countertops to be installed (coming soon), I moved the cooktop to an adjacent cabinet.
To do this, I lifted the cooktop a couple inches, moved it sideways and placed it onto a horizontal surface.
I did not disconnect it electrically and I did not turn its circuit off.
The cooktop was not turned on; its circuit still had voltage.
Later that day I received an electric shock, more than once, intermittently, before I found the loose green wire.
The cooktop's thick green cable and the building's romex single-strand ground wire (also green) had gotten disconnected.
By sliding the cooktop over, this moved the sheathed cable and this caused the ground wire (green) to get disconnected when the wire nut loosened.

I did not turn the cooktop on during that day.
I did not turn the cooktop on during that interval of time when it had been moved and its ground wire was not connected.
The cooktop was never turned on while I was looking at it to determine the problem and find the loose ground wire.
I am the only person who operates the cooktop; no-one turned on the cooktop.

Just f.y.i. since I placed the cooktop onto metal it was easy to receive shocks, without touching the cooktop's housing.
The shocks were not 230V in intensity.
I have enough experience to know that this level of voltage was not as big as 230V.
My guess is that it was much less than 115V.
My guess is that it was more than 20V, but how much more I don't know.

Here is the interesting part:
I'm wondering how an appliance which is not in operation can allow to leak or discharge or let loose that much current through its ground wire. The fact that there was more than one zap is the thing that is making me look into this a lot. Those who know more about these things can tell me if it is normal for a ground connection to be the route for excess charge to be released, -- AND more than once -- while the device is not ON and also has not been turned on between the intermittent shocks. At first I thought it was not normal but maybe understandable, but when i got another "intermittent" shock I really started thinking there may be something more to it. Now I'm wondering if it is constantly consuming electricity when not turned on, by sending pulses into the ground. I'm also wondering if this can cause premature failure.

This can become important at some point. An appliance should not be sending pulses into the ground wire. I'm willing to do some diagnosis with multimeters and power meters.

I like the __ and would gladly have another one of the same 24" size, if it comes to replacing this one.

---
.


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RE: shock from Ground (green) wire.

OK, just I sent it and within minutes I got a call back.

Here is the answer:

The appliance is always ready, always on, just like many other devices. He says there is a trickle voltage always. Nothing unusual. Been seen before.

The two hots are correctly connected to the two wires. Voltage is OK.

--So, I guess if ground is disconnected, an imbalance builds up and discharges as a zap.


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RE: shock from Ground (green) wire.

Yes, I was going to mention that these touch-control units are always 'on'. Else it would not respond to your touch.

You haven't stated the manufacturer. Is it European? The reason I ask is that it is common for the control electronics to use 120v eventhough the unit is 220v (or 230v).

The other thing is that the electronics in the unit is probably 'grounded' to the chassis. If not tied to the house ground, this chassis 'ground' will 'float' up or down relative to the true ground depending on the loads on the +120v and -120v attached to the unit. This is where you can get 'zapped'.

Next time you move it, turn off the power.


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RE: shock from Ground (green) wire.

Sounds like an explanation that I can sleep well with. The floating ground, close to ground.

I'm also going to clasp the sheath more securely to the wall box.

Yes it's imported from Europe, and as you guessed also, I didn't want to mention this until now.


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RE: shock from Ground (green) wire.

Those zany Germans... still mad about ze war... ;')


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RE: shock from Ground (green) wire.

How old ias the unit?

The present US and European standards do not allow the use of the safety ground to tie down the secondary of a step down transformer.

It was not prohibited a while ago, and some manufacturers did it this way.

The source importance for the leakage current is very high, so without a defect in the transformer it is not a hazard to personnel.


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RE: shock from Ground (green) wire.

Importance? Impedance?


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RE: shock from Ground (green) wire.

It was made for 230V - 240V in Europe, and that is what it gets here too... so I don't know what the meaning is of a stepdown transformer here. I mean, there is no transformer since it runs off 230V. Is this right?
-- It was made in 2008 or 2007.


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RE: shock from Ground (green) wire.

The source impedance for the leakage current is very high, so without a defect in the transformer it is not a hazard to personnel.

New keyboard.


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