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!

 

[a1guvner]

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!

When you say tests are within limits, what tests have you done so far?

 

[DNS1]

I assume you've done the insulation testing on the offending circuit.

 

[Marvo]

....who cannot get their boiler serviced due to a 5 volt current on their gas pipe when the upstairs lighting circuit is energised.

Can you explain a bit more about what test they performed and what readings they got when they decided to refuse to service the boiler? The '5 volt current' bit is confusing me.

 

[BrightSparkPaul]

polarity, pfc and ze tests have been done. Should I be doing a polarity and IR test on the lighting circuit, I am expecting a fault on this and unlike sockets, don't know where to start looking for the fault after I find it! Excuse the lack of technical terms, like I say I am newly qualified.

 

[BrightSparkPaul]

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!

 

[a1guvner]

polarity, pfc and ze tests have been done. Should I be doing a polarity and IR test on the lighting circuit, I am expecting a fault on this and unlike sockets, don't know where to start looking for the fault after I find it! Excuse the lack of technical terms, like I say I am newly qualified.

Def do the IR, it will then be a matter of working through the circuit methodically (think of the big picture)

 

[malcolmsanford]

Phantom voltage ???

If there is protective current leaking equipment in the house then you could quite easily be getting a small voltage on pipes through bonding ?

You have said something about upstairs light, if you remove all the cables from the CU for this circuit LINE/NEUTRAL/EARTH does it go away?

 

[malcolmsanford]

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!

God give me strength ....................gas plumbers

 

[BrightSparkPaul]

Phantom voltage ???

If there is protective current leaking equipment in the house then you could quite easily be getting a small voltage on pipes through bonding ?

You have said something about upstairs light, if you remove all the cables from the CU for this circuit LINE/NEUTRAL/EARTH does it go away?

If I turn that one circuit off (the upstairs lighting circuit) the voltage disappears completely (the gas engineer left his kew stick with the customer as proof!). All other circuits remain energised and the kew doesn't light up. When the upstairs lighting circuit is energised it comes back.

 

[malcolmsanford]

Look for a loose CPC, or perhaps that circuit don't have a CPC

 

[BrightSparkPaul]

Def do the IR, it will then be a matter of working through the circuit methodically (think of the big picture)

Forgive a dumb question, would it be easier to get Edison/bayonet testers to do this?

 

[BrightSparkPaul]

Looks like a big floorboards up job then..... Junction boxes ahoy!

 

[a1guvner]

Forgive a dumb question, would it be easier to get Edison/bayonet testers to do this?

Good to have some visual inspection as well

 

[Specialist]

Take a look under the Landing floorboards & see if you have any wires laying across pipes. Especially if they've had any Plumbing or Heating work done.

 

[BrightSparkPaul]

Take a look under the Landing floorboards & see if you have any wires laying across pipes. Especially if they've had any Plumbing or Heating work done.

Wires sharing access spaces with pipes everywhere! What's my best option IYO? Conduit/trunking? Starting to think this will be a frustrating/long/costly job! Oh well, work is work......

 

[Specialist]

What i'd be looking for to start with was any laid across heating pipes under the floor. Especially where they cross the joist, can't count the amount of times i've seen it done. Worst 1 I ever saw was a big country club, practically every joist had heating pipes / wires jammed together.
Before you get further into it, try moving the wires you've already found, away from the pipes & see what happens.

 

[BrightSparkPaul]

What i'd be looking for to start with was any laid across heating pipes under the floor. Especially where they cross the joist, can't count the amount of times i've seen it done. Worst 1 I ever saw was a big country club, practically every joist had heating pipes / wires jammed together.
Before you get further into it, try moving the wires you've already found, away from the pipes & see what happens.

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 !!

 

[a1guvner]

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 !!

Time to jump in with your IR tester before you rip the place to bits, get your overall IR upfront on the ltg ct if low then start seperating suspect parts of the circuit and retest and narrow it down

 

[Specialist]

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.