Discuss Getting 10v on Steel Capping in the UK Electrical Forum area at ElectriciansForums.net

impish15

Trainee
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Hi All

Recently bought a wandering lead and was practicing with it on a few of my relative houses checking if metal sockets / fittings / appliances had continuity etc and also checked 0v on some of the fittings. Couple of items with no continuity (CPC popped out at the back so re-terminated)

At one of the house there was exposed galvanised steel capping from the consumer unit up to the ceiling and I got a reading of 10v.

I couldn’t do any further investigation as I had to leave. Relatives are away currently so house is unoccupied.

What is the best way to tackle this? I was planning on removing the capping (obviously with power turned off) to see where the 10v could be coming from (possibly damaged cable insulation?). Once issue rectified replaced the steel capping with plastic trucking. Does this seem like a reasonable approach? Any other tests I can do? Test instruments I could use to assist me?

Also is steel capping usually exposed? I thought they were generally covered over when plastering.

Many thanks in advance
 
Capping on the surface does seem strange. Is it on an exposed brick wall where they thought it was getting plastered eventually?

What are you testing to? The earth bar at the consumer unit?

With the power off of course, you could IR test between each outgoing circuit and the capping to find continuity, but if you’re planning on replacing the capping with plastic trunking anyway, then forego the testing and just remove it carefully. You might just visually find a nailed cable or whatever.

I’ll just advise that, with a trainee tag, know your limits….
 
As @cliffed said. IR testing L and N together to the cpc bar is a good start. I was also going to suggest testing to the capping but was beaten to it!
I think I’d test anyway in case a cable has been pulled too tight and a Neutral is touching the capping. I’d like to know before swapping to plastic so I can see how bad it is and proceed accordingly.
 
Capping on the surface does seem strange. Is it on an exposed brick wall where they thought it was getting plastered eventually?

What are you testing to? The earth bar at the consumer unit?

With the power off of course, you could IR test between each outgoing circuit and the capping to find continuity, but if you’re planning on replacing the capping with plastic trunking anyway, then forego the testing and just remove it carefully. You might just visually find a nailed cable or whatever.

I’ll just advise that, with a trainee tag, know your limits….
That probably makes sense regarding them thinking it’ll get plastered over as one wall in the cupboard is plastered over but the other isn’t

I was testing to the MET in this instance assuming there would be no difference to testing to the earthing bar in the consumer unit but I can do that next when I’m down if necessary

Yes and noted regarding knowing my limits :)
 
As @cliffed said. IR testing L and N together to the cpc bar is a good start. I was also going to suggest testing to the capping but was beaten to it!
I think I’d test anyway in case a cable has been pulled too tight and a Neutral is touching the capping. I’d like to know before swapping to plastic so I can see how bad it is and proceed accordingly.
Yes same here i’d like to know also before changing to plastic so will definitely complete some testing first
 
I was testing to the MET in this instance assuming there would be no difference to testing to the earthing bar in the consumer unit but I can do that next when I’m down if necessary
Correct - should be the same result.

I had an interesting fault a year or so ago when I’d completely disconnected two legs of a ring for testing and was getting voltage of about 15v between the two neutrals - my tester alerted me and refused to test.
It turned out to be a N snagged on capping and a N from another circuit that was live snagged on same capping.
 
Correct - should be the same result.

I had an interesting fault a year or so ago when I’d completely disconnected two legs of a ring for testing and was getting voltage of about 15v between the two neutrals - my tester alerted me and refused to test.
It turned out to be a N snagged on capping and a N from another circuit that was live snagged on same capping.
This is good to know. I’ll bare this in mind whilst I investigate
 

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