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DaveS79

Live pipework

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DaveS79

Go easy on me chaps

 

Had a late call out last night. Customer reported shock on non electrical shower unit. Has previously had another electrician come to property who added some supplementary bonding but know refuses to come back to property and they have also had U.K Power come out to check earthing which they reported as fine, they did a few other tests and the only thing they could suggest it maybe is a fault from an adjoining property to customers pipework. This doesn't point to the issue for me as although the voltage is intermittent it is only present when customers lighting circuit is on. My first point of call was to check bonding was adequate and used wander lead from shower pipework to disconnected bonding conductors and both was below 0.05ohms. Because of limited time, access around property as some rooms rented to tenants also on my part insufficient lighting to provide while lighting disconnected I made a bit of a hash on what I think should of been next testing procedures i followed. In hindsight I think my next port of call should of been to follow crippler. I should of identified correct lighting cpc and line  R1 + R2 as far into circuit as could with limited access to areas of property. Once this was done then ir tested either with all dimmers off or with L and N to c.p.c. To note I did get a reading of 0.35M ohms on lighting line to a cpc at board but this wasn't at correct earthing terminal for circuit. Because of limited time again and lighting levels I didn't manage to get a true voltage to earth reading on pipework. How would you suggest this is best done? My thinking is that it wander lead from pipework to any other part of earthing other than main incoming earth I won't achieve this. So would need to isolate all circuits other than lighting disconnect main earth and test to this? The main thing I'm failing to see at moment is if bonding is indeed adequate and lighting circuit is rcd protected why would it not trip. They have mentioned that they are having a daily battle with mice but again if munched through cable this should trip it? At least when in contact with earth. One thing to note as well is that voltage detector is picking up voltage on groat work near shower unit and they haven't ever reported getting a shock before using shower it only seems to become present once the shower has been in use. Any point in right direction would be appreciated like I said they have had a few people round and no-one seems to be getting to bottom of it. 

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ProDave

I presume this is a HMO (multiple rented rooms)

 

Point out to the landlord their obligations to provide a safe environment ant they MUST give you all the access you need to test properly.  Go back in the daytime so you can see what you are doing with all the power off.

 

I will be shot down for this, but a neon screwdriver is damned handy for finding things that are live enough to hurt you, and more precice than a volt stick.

 

No 1 is test the earth bonding of the pipework and test at taps, showers, radiators etc to see if the earth makes it all the way, there may be a lot of plastic pipe work involved.

 

A full EICR is probably over due and really needs doing for this type of property.

 

The "live grout" needs a proper look, who know what nasties might be lurking behind there. What is on the opposite side of the wall to that?

 

I think the emphasis is you need to be allowed access and time to test properly without time constraints and without access constraints. The landlord needs to understand that.  I suspect that is why the previous electrician gave up.

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Murdoch

I investigated something similar once .... very nasty conclusion.

 

 

Barry the bathroom fitter refitted a bathroom for a very elderly customer. When he fixed the shower screen to the wall, he nicked the switched live from the switch..... meaning the frame of the shower cubicle was at 230v when the lights were on.... he had also replaced the central light with downlights and hadn’t bothered to make the cpc continuous either

 

The fault you are investigating needs finding and fixing

 

please let us know what you find

 

 

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Phoenix

You say theres a volatage present with the lighting circuit on? what is this voltage measured between? (If you can measure voltages between things where they shouldn't be while you are on site, you have a good chance of finding the causes, its when they only seem to be there when you are not that  its a pain to find)

 

You need to find which of the two items it was measured between is at a potential it shouldn't be at, a wander lead through the bathroom window to a long drill bit pushed in the garden away from any incomming services should provide a true ground reference

 

What is the earthing arrangement ot the property

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Geoff1946

Surely that 0.35Mohm measurement is your clue. It shouldn't matter which earth you were using at the panel. 

Find that fault and I reckon there's a high chance you will find the problem.

The leakage current won't trip an RCD but you will feel it, especially in wet conditions.

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DaveS79
16 hours ago, Geoff1946 said:

Surely that 0.35Mohm measurement is your clue. It shouldn't matter which earth you were using at the panel. 

Find that fault and I reckon there's a high chance you will find the problem.

The leakage current won't trip an RCD but you will feel it, especially in wet conditions.

I think your right geoff and thanks for advice. If i had been strict with crippler and proving this incorrectly terminated cpc was indeed my cpc for circuit causing fault I would of had much better chance of identifying it and so where problem originating.

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DaveS79

Thanks all for replies. I messaged customer and advised them that to get to bottom of fault I would need to get there in daytime so have sufficient time and lighting available and also would need to be able to gain access to all areas of house and rented out rooms. I feel like I have them a decent offer for this and said that if I couldn't resolve fault there wouldn't be charge. They haven't gave me access or got back to me so I suppose they will just have to pay electrician number 4 to look at it. Did my part can't offer more than that won't be going back

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binky

mice would not necessarily nibble through a cable, they tend to strip sides of FTE and seem to like the Live more than Neutral. With power off, I think I would use a wander lead to test between shower and lighting cct. Obviously wet grout will conduct more than dry - had somethig similar with a failing cable recently, where the outside wall was wet I could feel a tingle, yet RCBO did not trip. Fault turned out to be a cable that the insulation was failing on about 6 ft from the damp section of wall. 

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DaveS79
4 hours ago, binky said:

mice would not necessarily nibble through a cable, they tend to strip sides of FTE and seem to like the Live more than Neutral. With power off, I think I would use a wander lead to test between shower and lighting cct. Obviously wet grout will conduct more than dry - had somethig similar with a failing cable recently, where the outside wall was wet I could feel a tingle, yet RCBO did not trip. Fault turned out to be a cable that the insulation was failing on about 6 ft from the damp section of wall. 

Thanks Binky got a feeling that will come in handy at times with amount of similar type properties near me

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