Voltage from electric hob rings?

A friend complained of getting a shock from their ancient electric hob. This occurred when they grabbed at a metal handled saucepan on
the hob, while touching the stainless steel sink.
I measured 20 volts between the stainless steel 'spill ring' (which surrounds each of the hob rings) and a known earth (in this case, the earth terminal of a nearby socket outlet).
Deeming the age of the hob to be a likely suspect, I have since replaced this with a new hob. However, the voltage issue remains and I am still getting 20 volts from the new hob's spill rings! I tried phoning Moffat to see if this is normal, only to be told that they no longer operate a technical department for dealing with customer issues, which I find ridiculous.
So, can anyone here offer up any info or advice as to whether this is normal for an electric hob, or what might be the cause if this shouldn't be happening?
Many thanks, Dean.
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I would strongly suspect the earth has come adrift somewhere. As you have changed the hob, you need to check the earth in the supply cabling. At least that's what I would do first. There may be very high resistance leakage paths to earth as part of the design. Without an earth, the metalwork will "float" upwards in voltage. The meter will act as a potential divider in this case, so the 20V is a bit arbitrary. Certainly I had an identical problem with a washing machine, which turned out to be a disconnected earth in the supply cabling.
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Hi Bob.
Yes, the 'floating up' did seem to be an issue, as different rings gave various readings, and this did vary between 7 and 20 volts. I will check the continuity of the supply earth. Could it also be a breakage in the bonding to the sink?
cheers, Dean.
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wrote:

No, very unlikely, as the sink will be bonded all over the place and doesn't have a supply to it. Always suspect the thing with a power lead!
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It's not a requirement for the sink to be bonded. However since there should be main bonding to the incoming water main and this is nearly always under the sink it's pretty likely that the sink is connected to the mains earth.
I'd check the earth continuity to the hob first, then check to see how (if?) the sink is earthed.
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Chris Green

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deano laid this down on his screen :

It could be a number of things...
It could be the sink which lacks an earth and it has some voltage on it which you are measuring to the properly earthed cooker.
The cooker might lack an earth and your assumption is correct.
It could be that the spill rings are not earthed and are having some voltage induced onto them.
Th best way to work out which, is to make our measurements against a known good earth. Your 13amp socket should have a good earth on the upper larger pin - could you safely make use of that?
From a good earth you need to take another set of measurements. There should be no voltage at all as measured at the sink and the main body of the cooker.
If the spill rings are firmly attached to the metal body of the cooker, then there should be no voltage on those either. If they are not attached, then you can expect some voltage - but there will be no current behind the voltage - perhaps a few micro-amps at most.
All unearthed metal in or near the field of passing cable, will pick up a measurable voltage - that is perfectly normal and there is no danger.
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Harry (M1BYT) (L)
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In article

You'd first need to check the 'known earth' is indeed just that. It could be the faulty one. And don't just assume the house earth is good either.
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*Horn broken. - Watch for finger.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Poor earthing can certainly play hob with your hob. I had to search "hob" to learn it is an English cooktop. How about that. Y'know, Pearl Buck was one of the first people to recognize the value of grounding. She summed it up in her book, "The Good Earth." Tom
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On May 1, 12:17am, snipped-for-privacy@yesits.freeserve.co.uk wrote:

You are apparently not in the US, if you were I would say the main bonding jumper is missing, because I had the same thing happen to me on an inpection job except I laid my metal tablet on the electric stove and touched it and the metal sink at the same time. A hot wire was pinched at a pump cover in the basement and the main bonding jumper was missing so the breakers could not trip. All the water pipes were at 120 volts, and the stove was grounded using the neutral so there was 120 volts from the stove to the metal sink.
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wrote:

You are apparently not in the US, if you were I would say the main bonding jumper is missing, because I had the same thing happen to me on an inpection job except I laid my metal tablet on the electric stove and touched it and the metal sink at the same time. A hot wire was pinched at a pump cover in the basement and the main bonding jumper was missing so the breakers could not trip. All the water pipes were at 120 volts, and the stove was grounded using the neutral so there was 120 volts from the stove to the metal sink.
Nasty! Except here it would be the supply earth was missing, a live wire was pinched and the RCD's didn't trip as the earth was missing and the pump was floating (except an RCD might have). All the water pipes would have been at 240V, as would the cooker to the sink. Ah, two nations divided by a common language :o). Still, Volts is volts and missing earth/bonding just as dangerous either side of the pond.
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On 1 May, 09:17, snipped-for-privacy@yesits.freeserve.co.uk wrote:

Thanks for all the replies everyone. I must admit, I'm very suspicious of the electrical supply to my friends flat. He's on the top floor of a converted house (on the 4th level). The current installation is very out-dated and needs modernising. It doesn't even have it's own consumer unit, in the flat. Just an old type switch down in the basement electrical cupboard!
Before putting in the new hob, I also measured the voltage between the live feed of the hob supply cable and the earth terminal of the socket outlet, this measure 240 volts dead. There was no volts between the neutral and earth supply wires and the socket outlet... does this indicate anything?
If there is a possible break in the earth supply to the hob feed, then I will try running a 'fly lead' straight up from the earth block in the basement, to the hob and see if that removes the present voltage leak from the spill rings. I do still wonder however if this is normal from the spill rings, as no other part of the hob is emitting voltage.
It's a long way for me to go to the flat, so I want to have a good idea of the likely cause before I next go there and try to remedy the fault.
Cheers, dean.
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deano wrote:

You've got a missing earth somewhere. The resulting risk varies from one appliance to another, and is highest for hobs and showers.
Lack of a CU in the flat, and lack of a CU even in the basement - if I understand you rightly - makes the odds of a very dodgy installation high.
I'd start by checking the basics, installation fusing, earthing, cable condition etc, and it sounds like the installation would fail even on that level.
The trouble with unearthed hobs: you're holding boiling water and frying fat, so even the slightest shock can cause severe burns. And hobs use heating elements, which are probably the most likely item to become leaky. And they use water, and a damp environment increases risks further.
Resolving the worst of the situation would mean finding the supply feed to the flat and fitting a CU, and checking the earth fed to the flat. Sounds like there will be other things to sort as well. It might be too big a job for you, don't know.
NT
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wrote:

If this one switch is providing ring main power, cooker supply and lights all as one big spur then you may have some "issues" (or your friend does).

That would depend on the earthing arrangements of the supply to the property - there are many others here wildly more proficient than I at explaining it!

Nonetheless, the metal parts of the cooker should be earthed so that such leakages do not manifest themselves as volts. No combination of appliance and installation should give you a shock, however small. You have replaced the hob so it cannot be corrosion and no hob would be designed like that. Providing a second, good earth to the hob to try it out seems the best bet to proceed with diagnosis
You can only help the situation (or have no affect on it) by installing a separate earth - whether the whole installation is cr*p or not and whether or not your earth is untidy!
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