Water pipes & wooden structure showing voltage

[captaincaveman]

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?

 

[PEG]

Hi,i would begin,by doing complete IR testing,on all conductors,and start to narrow things down.

 

[buzzlightyear]

possible leaking of voltage some where .

 

[Octopus]

You say the gas and water bonding are present .....

I would be getting my wander lead out and checking for earth continuity on a variety of points ...

 

[static zap]

Is the cpc intact on the lighting .
(A rare thing with some vintages)
(Isolated part could well still be picking up stray voltage and re-disributing it )

 

[buzzlightyear]

why don't you pm PEG he is nearest to you .a couple of beer tokens & a bargain bucket.

 

[buzzlightyear]

The voltage lowered on isolating the sockets & disapeared totally on isolating the lights.

is the lighting and the sockets been bridged some where .

 

[buzzlightyear]

has some one rang miss maple yet.

 

[Deleted member 26818]

Are there any high voltage power lines overhead?
I have yet to see wood that will conduct ELV.

 

[dmxtothemax]

As much as we electricians would prefer to have no currents flowing in the earthing system, that is seldom reality ! Not many electrical systems are perfect, so small currents in the earthing system are not unusual. Fixing such systems can be a big job. so to a large degree it is tolerated.usually small currents are not fatal, but a small tingle does seem to bother some people.

 

[PEG]

why don't you pm PEG he is nearest to you .a couple of beer tokens & a bargain bucket.

A noble and generous suggestion - but unlikely...

1) I haven't touched alcohol since i was 15

2) He is at a paying gig,and if his customer asked who and what i was,the lie i would have to tell,would be my first

3) I couldn't start my old Patrol,until the OP had inserted the word "approved",in front of his second test instrument description

 

[Wilko]

Hi - Voltpen not helpful here I'm afraid. As mentioned above, I'd use wander to confirm boiler and all those pipes effectively bonded. I suspect a/several circuits have floating CPC as well as IR problems you've already found.

 

[static zap]

...... As mentioned above, I'd use wander to confirm boiler and all those pipes effectively bonded......

Kev the kitchen fitter ,may have messed up some-one elses cunning plan , with his plastic pumbing !

 

[marconi]

To help, please could you describe how you measured the potential difference with your approved voltage tester? Between which two points does the potential difference exist?

What other pds have you measured in this house? eg: MET-N, MET-Water Intake, MET-gas, Boiler casing-MET? Boiler cpc at FCU - pipework.

 

[PEG]

I trust the OP will be giving us an update,or folk are going to start the big supposition stampede...like a practical joking child,with two fluffy angora guinea pigs,in wheel,powering a van de graff generator...

See what i mean...

 

[buzzlightyear]

possible leaking of voltage some where .

isn't it amazing that people in the dark shadows ,never say any thing ,but, put old .
I call them curtain twitches!

 

[Deleted member 26818]

isn't it amazing that people in the dark shadows ,never say any thing ,but, put old .
I call them curtain twitches!

Probably a plumber.

 

[Jim_e_Jib]

isn't it amazing that people in the dark shadows ,never say any thing ,but, put old .
I call them curtain twitches!

Yep, sorry about that. Scrolling on a touch screen you see. Picked up my blow torch the other day, burnt my fingers and am now more ham fisted than ever.

 

[PEG]

Yep, sorry about that. Scrolling on a touch screen you see. Picked up my blow torch the other day, burnt my fingers and am now more ham fisted than ever.

Aaaah Har! ... He's a plumber!

 

[captaincaveman]

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