Water pipes & wooden structure showing voltage

captaincaveman

captaincaveman

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Hi. Penny for a thought anyone. I'm still in holiday mode from yesterday...

Just been to a house after a plumber refused to touch the boiler (not before getting his £200 call out charge) saying there was an electrical fault and showing the customer his voltage pen light up on the water pipes & attic wooden joists saying there "was 20v" through them. The customer asked me to check it over before getting a plumber back.

Indeed on checking my 5V+ pen lit up on both pipes & joists and my voltage tester displayed voltage but of a negligable amount <12v.

The boiler is situated in a seperate part of the house with both water pipes and cables running through a narrow passage above a room joining the two main parts the house.
-TNCS system
- The voltage lowered on isolating the sockets & disapeared totally on isolating the lights. The cabling is messy and could be wrapped around the pipes in places (can't access to see full run).
My first suspicion was induced voltage from the close proximitary of the pipes and cables but that didn't ring right with the joists so I did some tests.

- Gas & water bonding is present.
- IR test on sockets >2Mohm
- IR test on lights 0.23 Mohm

The last time I came across continuity through walls it was a hidden nail in a skirting board catching the r1 to a socket so with the lights failing the IR test I'm thinking a nail etc could be the cause, but, When I reenergised the system less this failed lighting circuit I still have some voltage on the joists / pipes.
Now I'm thinking maybe it's both - induced voltage & a "nail"?
I've got to return to try and locate the light failings but wondered if anyone had any thoughts on the pipes/joists issue?
 
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Hi guys. Sorry for the delay. Busy, busy, busy.
Thank you for your suggestions/questions/grumbles ;-)
To answer (in order):

Static zap - The cpc is continuous to fittings.
But there are two unaccessible wall lights behind an artificial wall apparently.

Buzzlightyea - I have not seen any readings or evidence to suggest bridging between sockets & lighting.
Also Miss Marple won't talk to me after finding me in bed with Jessica Fletcher.

spinlondon - No powerlines

dmxtothemax - The issue really is the customer doesn't want to waste another 2 ton on a plumber to just walk away again and is adamant he wants the issue dealt with first

peg - Edit: Indeed on checking my volt pen lit up on both the approved pipes & approved joists and my voltage tester displayed voltage but of a negligable amount <12v ;-)

wilko - yeh. I agree. I only use my volt pen to trace cables in walls. (it's a 5v+ adjustable one imported from the u.s. and is brill at locating cables). I was just trying to put myself in the plumbers shoes to see what he was talking about. saying that it's never picked anything up on wood before hmmm.

marconi - I tested all the above with exception of boiler cpc at fcu which was a distance in the hall (boiler in the attic). I tested to the cpc at the boiler instead. I also tested with my megger (which is 10v+) but no reading as I presumed.

I'm going back soon to look at it again. I'm going to start by sorting the lights out due to the IR failure. It may be or may not be connected. Like I say it's not the first time I've found a screw ever so slightly piercing a live conductor and affecting the surrounding structure. The customer put a light up recently so it might be he's put screws into the ceiling and also the cable.
I'll let yous know how it goes and any findings.

Cheers & take care
 
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captaincaveman said:
Hi guys. Sorry for the delay. Busy, busy, busy.
Thank you for your suggestions/questions/grumbles ;-)
To answer (in order):

Static zap - The cpc is continuous to fittings.
But there are two unaccessible wall lights behind an artificial wall apparently.

Buzzlightyea - I have not seen any readings or evidence to suggest bridging between sockets & lighting.
Also Miss Marple won't talk to me after finding me in bed with Jessica Fletcher.

spinlondon - No powerlines

dmxtothemax - The issue really is the customer doesn't want to waste another 2 ton on a plumber to just walk away again and is adamant he wants the issue dealt with first

peg - Edit: Indeed on checking my volt pen lit up on both the approved pipes & approved joists and my voltage tester displayed voltage but of a negligable amount <12v ;-)

wilko - yeh. I agree. I only use my volt pen to trace cables in walls. (it's a 5v+ adjustable one imported from the u.s. and is brill at locating cables). I was just trying to put myself in the plumbers shoes to see what he was talking about. saying that it's never picked anything up on wood before hmmm.

marconi - I tested all the above with exception of boiler cpc at fcu which was a distance in the hall (boiler in the attic). I tested to the cpc at the boiler instead. I also tested with my megger (which is 10v+) but no reading as I presumed.

I'm going back soon to look at it again. I'm going to start by sorting the lights out due to the IR failure. It may be or may not be connected. Like I say it's not the first time I've found a screw ever so slightly piercing a live conductor and affecting the surrounding structure. The customer put a light up recently so it might be he's put screws into the ceiling and also the cable.
I'll let yous know how it goes and any findings.

Cheers & take care
Click to expand...

The pipes and joists,may well be approved by someone,but it is the AVI and where you stuck it,that i was alluding to...

I feel an Eric Morecambe/Piano note moment,is approaching :)
 
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Just an update for anyone whose bored enough to care.

I returned to sort the lights out which wasn't easy as I couldn't access the damaged section (without pulling the sloping ceiling down) so I replaced that section of cable and all circuits tested ok.

Although my vpen/tester were still showing a minimal voltage in the woodwork, pipes etc, I was satisfied the installation was safe.

Strangely though, I did a job across the road / cul-de-sac and out of curiosity my vpen lit up on the front (plastic) doors which made me wonder, as both houses are tncs, If there is a bad termination with the distributors neutral would that make it possible for a small amount voltage to earth back through the water pipes etc? and could this really affect the structure? and do I really have a life? - I can answer the latter, I think... I was going to say 'or do I need a new pen?' but I'm minded that the reason I was called out the first time was because a plumbers pen was "showing 20V on the woodwork"...

Sod it. I might go back to 'check it again' and get some more money to pay for this years annual regulation update...
 
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