Tingle - possible cause? Floating Earth?

[unopened]

Hi all,

I've recently had a consumer unit replaced in my flat, moving from cartridg e fuses to RCBOs.

Following this, it looks like I may have an earth problem. While loading t he dishwasher, I was leaning on the worktop with my hand on the stainless s teel sink. On touching the inside of the diskwasher, I got a tingle.

So, I got out my multimeter and an extension cable and did some checks.

The potential difference between the inside of the dishwasher and the sink is approximately 55 to 60 VAC.

Checking the earth of the socket the d/w was plugged into, it too has a PD of about 55-60 VAC with the sink.

So I checked back to the heating radiators, and the PD between the electric al earth in the socket service the d/w and the radiators is alos approx 55-

60 VAC.

Checked the same back to the main water incomer - also PD of 55-60 VAC.

Now, the d/w is on a separate way to other equipment in the kitchen, so I c hecked other kitchen sockets, and yes, you've guessed it, PD of about 55-60 VAC between electrical earth presented at the socket and the water pipes. And the same with stuff on yet another way in the consumer unit.

Is this normal for a an installation after RCBOs are installed? (I suspect not, but it would be nice to have this confirmed).

If not normal, what's the likely cause? Obviously, I'll need to get the pro fessional electrician back who installed the new consumer unit, but I want to make sure I ask the right questions. Is it possible to simply forget to connect the protective earth through the consumer unit, so the 'downstream' side simply has a floating earth? So it could be a simple 'forgot to conne ct up a final wire'? That is, a could a missing single connection affect al l ways?

As it is a block of flats, my consumer unit is in a set of cupboards next t o each other in the common corridor outside the flats - one consumer unit p er cupboard. The neighbours have not replaced their cartridge fuse consumer units, so still have an exposed earth terminal in their cupboards, and I w as able to confirm that the all the metal cupboards (including mine) are co nnected to a protective earth which has zero PD with respect to the water p ipes.

The RCBO protecting the d/w is a snazzy EATON one, which can give an indica tion of the leakage current it sees by flashing a multicoloured LED in a co de in 'test mode'. On testing this, it gives a suspicious (to me) reading o f 0 mA leakage; as does the RCBO covering the other kitchen equipment. To m e, this seems to good to be true.

Comments and advice welcome, if if someone tells me I'm worrying over nothi ng.

Many thnaks,

Sid

[Tim Watts]

Yes - you have an earthing problem somewhere.

Either your plumbing is earthed (directly or indirectly) and your main earth is missing, or your plumbing is not earthed at all.

Nope - someones dropped a connection somewhere. RCBO's make no measurable difference to the bonding.

That sounds like your main earth is missing - which is very very bad!

It's hard to be sure by a written account - but if I were you I would call the electrician back asap. Or any electrician.

There's no way the installation should have been left with incorrect earthing (either main earthing failure or bonding failure) - that's why they (should) test after a CU upgrade!

[pcb1962]

And until you do that stay out of the shower.

[jrwalliker]

+1

You have done some very nice diagnostics. The observation that your water pipes appear to be bonded to the metal cupboards in the corridor very stron gly suggests that it is your main earthing connection in the new consumer u nit that is missing.

A faulty appliance shorting live to "earth" would leave all metal appliance s live relative to your plumbing. One of your RCBOs might trip from the lea kage current in the system, but not necessarily until you completed the cir cuit with your body at some time later. You would then get an unpleasant b ut probably non-fatal shock in the short time before the RCBO trips.

Your electrician will want to come very quickly to remedy this. He will de finitely not want his competitors or whatever body he is registered with to find out that he has made such a basic mistake compounded with failing to test the installation.

John

[Tim Watts]

It does seem quite likely doesn't it.

Personally, I would call in another electrician if I suspected this - and I would ask him to document what was found.

Then I would get on the phone to the original electrician's professional body (probably NICEIC, could be NAPIT or ELECSA or less likely a couple of others).

Because if this transpires to be the cause, there is NO EXECUSE for leaving an installation like this.

It's a mistake compounded with no testing at the end.

[Harry Bloomfield]

[e-mail] used his keyboard to write :

It reads as if you potentially have a rather serious problem and my first question is - was the guy who did the job actually qualified to do it? Having completed the job, he should have carried out tests, which would have highlighted this issue.

The voltage or potential difference, could be due to lack of an earth at your sockets, or it could be that there is potential on your pipework.

In other words you could be getting the tingle from the pipes, rather than from the dishwasher. To prove which, connect a meter probe between a length of metal pushed into the soil and measure between that and pipes then dishwaher. Which ever test shows voltage, is obviously lacking an adequate earth.

[Tim Watts]

He did mention he'd tested to his neighbour's MET (main earth terminal) as the consumer units are in a riser cupboard in the shared hallway.

[spuorgelgoog]

Probably :-)

I had an entire landlord's supply left unearthed by a NICEIC registered firm. At least, it was their stickers everywhere.

Owain

[Harry Bloomfield]

I did realise that, but in a situation like this it is best not to assume that anything can be relied upon, except the ground / soil, as a valid reference point for earth.

[Brian Gaff]

Yes it may only be a not very well tightened screw somewhere, but it needs fixing as it could get worse. I've never noticed this with any electronic circuit breakers of any type as they do not really have anything that can leak. Maybe pull them all and see if it changes, but I doubt it. Brian

[Harry Bloomfield]

I would suggest NICEIC would have little or no interest. They are there simply to collect money from the trade, rather than deal with complaints from the public in regards to dangerous work carried out by their registered tradesmen and contractors.

I would suggest involving a second independent engineer to actually determine the cause and carry out repairs. He should also fully document it - then recover the cost from your fist contractor via the courts if necessary.

[John Rumm]

I would concur with the other diagnosis - you have a problem, and its the electrician's job to fix it _NOW_ if not sooner.

One typical source of floating voltages like this can be the noise suppression input filters on the mains appliances. They often capacitively couple the L & N to E. If the E connection is floating then it will tend to try and sit somewhere about half mains potential. The impedance is very high - so you are unable to get a shock from this coupling, but you can feel it, and it is indicating some other problems is present.

Its possible to forget (due to negligence / brain fart etc). It would be impossible to not detect during testing however unless he did not test it (gross negligence!)

You should have received a test sheet, that among other things would indicate the Earth Loop Impedance (ELI) of each circuit. Did you get this?

Your main earth should also be bonded to this...

This implies that even if your main earth was not particularly good (e.g. a TT earth*), you would not expect to see the difference between circuit earths and the pipework etc.

Keep in mind the "leakage" it sees is only the imbalance between L & N. The only bit of a DW that naturally shows leakages as such is a small amount (possibly < 1mA) for the input filtering, and perhaps a bit more when the heater is working (depending on the age of the element) it will not necessarily (depending on the flavour of RCBO) have any earth connection, and be able to detect a rise in earth voltage.

All in all, congrats on a good set of diagnostics! ;-)

[unopened]

dge fuses to RCBOs.

the dishwasher, I was leaning on the worktop with my hand on the stainless steel sink. On touching the inside of the diskwasher, I got a tingle.

k is approximately 55 to 60 VAC.

D of about 55-60 VAC with the sink.

ical earth in the socket service the d/w and the radiators is alos approx 5

5-60 VAC.

checked other kitchen sockets, and yes, you've guessed it, PD of about 55-

60 VAC between electrical earth presented at the socket and the water pipes . And the same with stuff on yet another way in the consumer unit.

t not, but it would be nice to have this confirmed).

rofessional electrician back who installed the new consumer unit, but I wan t to make sure I ask the right questions. Is it possible to simply forget t o connect the protective earth through the consumer unit, so the 'downstrea m' side simply has a floating earth? So it could be a simple 'forgot to con nect up a final wire'? That is, a could a missing single connection affect all ways?

to each other in the common corridor outside the flats - one consumer unit per cupboard. The neighbours have not replaced their cartridge fuse consum er units, so still have an exposed earth terminal in their cupboards, and I was able to confirm that the all the metal cupboards (including mine) are connected to a protective earth which has zero PD with respect to the water pipes.

cation of the leakage current it sees by flashing a multicoloured LED in a code in 'test mode'. On testing this, it gives a suspicious (to me) reading of 0 mA leakage; as does the RCBO covering the other kitchen equipment. To me, this seems to good to be true.

Just a quick update. I've left the original text as context, apologies if I should have snipped some/all.

I have contacted the electrical firm that did the work - the electrician wh o did the job is being pulled off other work to 'come in for an interview', and a different electrician is coming out 'first thing' tomorrow to look a t the issue.

I have double-checked, and the problem is still there - thankfully it is no t a heisenbug.

The question on paperwork is interesting. I wasn't present when the work wa s done, and I was told I would get the necessary documentation later: of co urse, I got the bill, but I don't seem to have a copy of any testing docume nts. I will be very interested to see what the outcome is tomorrow.

The chap who did the work had some interesting working practices - I had to come back to the flat briefly while he was adding a new wall-mounted socke t, and he was working alone, live - that is, he had not isolated the circui t he was working on. I was a tad surprised at this.

Many thanks for the advice, and the compliments on my diagnostics.

Regards,

Sid

[Tim Watts]

OK - that sounds like the firm is taking this rather seriously. Good.

Then he's a steaming lunatic. This does not seem inconsistent with your other problem.

If they find a problem, you should insist they perform a complete test and inspection of the whole installation at their expense - who knows what other corners had been cut?

Also that will generate you a fresh set of test documents (not technically an EIC (installation certificate) but the numbers will be the same.

[Dave Liquorice]

INAE but would the ELI test of each *circuit* pick up a disconnected main earth to the CU or disconnection between the Main Earth Terminal and the suppliers earth?

[Harry Bloomfield]

Tim Watts has brought this to us :

I wouldn't put it quite that strongly, live working is not that unusual and on even higher voltages. Often the only way faults can be found, is with live working.

[Tim Watts]

It is in domestic environments - especially when he's on his own - that breaches pretty much all the H&S directives!

The main point is he's exposing himself and the customer (who was there for that bit) to an unnecessary risk.

[spuorgelgoog]

Live *testing* is different from live *working*.

Although I was a bit reckless earlier, but leaving the circuit energised is the simplest way of finding out if I've breached the insulation ;-)

Owain

[Rick Hughes]

especially if playing electric guitar at the time

[John Rumm]

It ought to... with a disconnected earth (and what looks like main bonding disconnected as well) the earth at each circuit is going to look like its open circuit as well.