Earth is reading 10v when tested

[kentmonkey]

I had a Mira engineer round today to service the shower. The shower was installed by the previous owners.

When he turned off the electricity supply to the shower and removed the shower casing and tested the L to E and E to N, he found that the Earth cable was showing a 10.8v reading. Oddly this dropped to about 10.6 if I turned off the bathroom lights and then back up again to 10.8 when I turned the lights back on.

Is this something to worry about? I'm assuming yes but would like to know more about it. Also is it likely to be something wrong with just the shower, or the whole electrics in the house?

We do suffer with lights keep going up and down. Not much, a dip followed by an immediate return to full brightness now and again (we're talking milliseconds), and the lights upstairs seem to take about 1 second to fully come on (they come on about half, and then go to full brightness after about a second, regardless of the bulb used in them) but can't think that this has anything to do with it. Although, in itself, probably an issue.

Advice gratefully appreciated.

 

[Taylortwocities]

So, this voltage.
What was this measured between?
the earth and what?
Live, neutral, a pipe, the end of his finger???

What sort of supply do you have in Kent? A photo of your incoming supply cable head might help.

 

[kentmonkey]

Live to earth and Earth to neutral. He used one of those tester kits to check.

In the end he disconnected the cables so he could work on it and then reconnected them, but I'm just a bit worried that there's 10v of electricity coming down the earth cable. Or somehow being transferred to the earth cable for the shower alone.

I'm guessing you mean what supply cables do we have coming into the house? Overland cables, supplied from the poles outside coming in at around roof level but no idea as to the cabling itself.

If you haven't guessed, electrics are not my strong point.

 

[JohnW2]

So, this voltage. What was this measured between? the earth and what? Live, neutral, a pipe, the end of his finger???

He seems to be talking about a N-E measurement. Assuming that was an 'off-load' measurement, if his supply is anything other than TN-C-S, I imagine that 10.8V is just about credible, without any problems, isn't it? Of course, there also may be 'problems'!

Kind Regards, John

 

[ericmark]

There will when power is being used always a slight difference between the bonded earth and neutral this in some cases could be higher than you are measuring but in a bathroom 12 volts seems to be regarded as maximum voltage between two touchable surfaces and normally one would be looking at less than 2 volt.

However to test we don't measure the volts but we measure the ohms between line - neutral and line - earth to see if they will under fault conditions allow enough current to flow to ensure it will auto disconnect.

So in real terms the voltage does not tell us very much. It is the loop impedance (that's AC resistance) that tells us if the bonding is up to scratch. It would to me ring alarm bells but until a low ohm ohmmeter (uses at least 200ma to do the test) or a loop impedance meter is used there is no real way to know if dangerous or not.

The neutral - line voltage with a TN-C-S system is likely less than 2 volt but with a TT system it could be as high as 50 volt although that would be unusual.

So likely with TT nothing to worry about but with TN-C-S it would really be a cause for concern. One would hope some one as part of their job who disconnects the power would know enough to have advised you as to if further work was required.

 

[JohnW2]

The neutral - line voltage with a TN-C-S system is likely less than 2 volt ...

Do I take it that you mean 'neutral-earth' (rather than 'neutral-line')? If so, if measured off-load, the N-E voltage will surely be zero with TN-C-S?

Kind Regards, John

 

[kentmonkey]

Thanks for the reply, appreciate it.

The neutral - line voltage with a TN-C-S system is likely less than 2 volt but with a TT system it could be as high as 50 volt although that would be unusual.

So likely with TT nothing to worry about but with TN-C-S it would really be a cause for concern. One would hope some one as part of their job who disconnects the power would know enough to have advised you as to if further work was required.

With regards to the TT and TN-C-S, I don't actually know what this means, sorry. How could I tell what I have (or can I? Is that a job for someone more competent?)

I was going to get an electrician out next year to look at the board as I don't think the electrics in this place have all been updated. Plus the board is about 9 feet up the wall in the garage, meaning that you have to get up on a ladder to disconnect anything. Which, in darkness, isn't particularly handy.

What worried me most was it's a shower. With water. And potentially not earthed or not earthed properly.

 

[Johnmelad]

With regards to the TT and TN-C-S, I don't actually know what this means, sorry. How could I tell what I have (or can I? Is that a job for someone more competent?)

//www.diynot.com/wiki/electrics:main_equipotential_bonding

 

[kentmonkey]

Heh. Job for somebody more competent then!

 

[JohnW2]

With regards to the TT and TN-C-S, I don't actually know what this means, sorry. How could I tell what I have (or can I? Is that a job for someone more competent?)

Would it be possible for you to take a photo of the place where the supply enters your home and connects to tyhe meter etc.?

Kind Regards, John

 

[kentmonkey]

I can try but as I say it's 9-10 feet up a wall and even with the ladder I have, I'm on tip-toes to reach it. I can try with a camera though and see what comes out.

 

[JohnW2]

I can try but as I say it's 9-10 feet up a wall and even with the ladder I have, I'm on tip-toes to reach it. I can try with a camera though and see what comes out.

That's very high! However,particularly if your camera has a zoom facility, even a picture taken from ground level (i.e. with the camera maybe 5-6 feet above ground) may well give us some good clues.

Kind Regards, John

 

[ban-all-sheds]

I can try but as I say it's 9-10 feet up a wall

The main fuse and the meter are not, surely?

 

[kentmonkey]

The fuse board is, the meter is further down (eye level).

Can I take a photo of the meter, would that suffice?

I realise dealing with me about electrics is like pulling teeth, so appreciate the help.

 

[Chri5]

I can try but as I say it's 9-10 feet up a wall and even with the ladder I have, I'm on tip-toes to reach it. I can try with a camera though and see what comes out.

Why so high up, is it a overhead supply or is yours part of a set of terrace property with a railway line of cables serving each property via the same height and position?

Is the board with the house fuses wire style or switch?

The more detail you give the better. When do you think the property last had major electrical work?