Voltage on gas pipe to boiler - newly qualified question!!

[BrightSparkPaul]

Hello all, be gentle I am newly qualified and this is my first post! I have a customer who cannot get their boiler serviced due to a 5 volt current on their gas pipe when the upstairs lighting circuit is energised. All the supplemental and equipotential bonding seems ok, tests are within limits when the circuit isn't energised. There are a few issues with labelling on the CU but other than that all seems to check out OK. Is my best way forward to get at all the wiring and check for some sort of contact here? No obvious contact in visible places and the pipes are not showing any voltage downstairs. Can only assume that somewhere the lighting circuit is 'leaking' somewhere. Any advice on how some of you guys would proceed would be most welcome!

 

[MarkieSparkie]

I've moved most of the visible wires away. There's one area where some lighting wiring shares an entry point with pipe work and has been plugged with expanding foam, I'm guessing that's a possible hot spot !!

Some expanding foams (and Gripfill) have an adverse reaction with PVC cable insulation causing it to breakdown.
I had a situation a few years ago where an outgoing lighting cable shared an access hole with the incoming overhead supply cables. This hole had been filled with expanding foam causing breakdown of the cable insulation allowing leakage from the incoming line to power the lighting circuit. The first indication of the problem was when the switch cable was about to be cut to length and the cutter blades switched the lights ON even though the installation was "safely isolated" at the DB main switch.

 

[Edd]

I would be tempted to use the volt stick he left,, and start splitting the circuit up till the stick goes out,,, it may point you in the right area... split what you think is thge middle does it still light and work from there..

 

[Golden_Boy]

The gas fitters simply stick the pen tester on the pipe, therefore it is the potential difference between the gas pipe and where they are stood. Or is that a little simplistic?

Maybe the gas fitter was at a voltage and the gas pipe was at earth potential.
I would blind them with science given half the chance....

 

[Specialist]

I have one too and can confirm that it's quite insensitive to phantom voltage, but it's not infallible.

No mate: I know it's not infallible but compared to most of them it's pretty good, my first one got stood on by some lump of a Builder & the only 1 I could get quickly was a Di log. Damned thing would show the air was live, took it back & they gave me some other make & that picked up ghost voltages all over the shop. so went & bought another MK & am sticking with them.

 

[Specialist]

I would be tempted to use the volt stick he left,, and start splitting the circuit up till the stick goes out,,, it may point you in the right area... split what you think is thge middle does it still light and work from there..

Been wondering about that, what sort of Gas fitter gives up his good working tester to a client.

 

[Golden_Boy]

No mate: I know it's not infallible but compared to most of them it's pretty good, my first one got stood on by some lump of a Builder & the only 1 I could get quickly was a Di log. Damned thing would show the air was live, took it back & they gave me some other make & that picked up ghost voltages all over the shop. so went & bought another MK & am sticking with them.

I am the opinion that ALL non contact "meters" are a waste of space............

 

[BrightSparkPaul]

Been wondering about that, what sort of Gas fitter gives up his good working tester to a client.

He's a funny old sort, I met him a couple of days ago. Apparently British gas hand them out like sweets.... He's got 4!

 

[Richard]

Hi,

Can you be more specific as to what you have 5V between? You are testing between the Gas pipe - and What? to get 5V.

Thanks

 

[PC Electrics]

It's British gas, they use non contact kew sticks, then recorded the voltage using a metrell I think. The kew stick lit up, which is fail one for them and they won't go anywhere near it now!
none of my testing equipment can register a proper voltage (kewtech kt64 and fluke avi multi) but the kew stick is definitely lighting up!

The gas fitters simply stick the pen tester on the pipe, therefore it is the potential difference between the gas pipe and where they are stood. Or is that a little simplistic?

Yep, I've had exactly this with a client. Absolutley nothing wrong anywhere. In the tank area where the gas 'engineer' was waving his stick, there were wires for the immersion and also ch controls.

What voltage did you measure between the pipes and met?
what was your continuity from the pipes to met?
was bonding continuity satisfactory?
was Ze satisfactory?

There's four pages here and unless I'm blind I cannot see a single test result anywhere.

I'll put up a tenner there's nothing wrong.

 

[GLENNSPARK]

Yes mate: Thats definately a possible hotspot, something has me a bit confused. What sort of non contact tester picks up on 5 volts ?. then as a1 says i'm afraid it's time for the Megger & a nice little tracing session.

this is what i thought spesh when i first saw it.....more like 120V??.....so a dangerous potential for a start....

 

[GLENNSPARK]

I am the opinion that ALL non contact "meters" are a waste of space............

look..it aint a "meter" ....isn`t a volt stick...and should never be treated as such....but they aint a "waste of space"....as long as you know the limitations of em...and always remember that they aint intrinsically safe and should never replace an approved voltage indicator to GS38....for the purposes of doing a safe isolation etc.....

 

[Golden_Boy]

look..it aint a "meter" ....isn`t a volt stick...and should never be treated as such....but they aint a "waste of space"....as long as you know the limitations of em...and always remember that they aint intrinsically safe and should never replace an approved voltage indicator to GS38....for the purposes of doing a safe isolation etc.....

Meter in quotes you will notice..... As for intrinsically safe ??? what explosive atmosphere would you encounter in a domestic situation?

 

[GLENNSPARK]

Meter in quotes you will notice..... As for intrinsically safe ??? what explosive atmosphere would you encounter in a domestic situation?

alright then......so would you just wave a volt stick over it....and consider it "tested" then eh???

 

[imago]

what explosive atmosphere would you encounter in a domestic situation?

Working in the bathroom the morning after a Guiness and curry night for the owner maybe?

 

[Golden_Boy]

alright then......so would you just wave a volt stick over it....and consider it "tested" then eh???

NO I would inspect/test fully with the correct equipment, Certainly NOT a non contact instrument of any kind.
Intrinsically safe by the way means that equipment is safe to use in explosive atmospheres.