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!

 

[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.

 

[a1guvner]

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

Your tester will give you clues quicker than exposing questionable areas and doing visuals

 

[BrightSparkPaul]

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.

The flukes and kew techs both seem to light up around 6v.....

 

[Specialist]

The flukes and kew techs both seem to light up around 6v.....

That's brilliant for a Tester that's not supposed to light up below 100v, think i'll stick to my MK tester. What was the result of your insulation test on the upstairs lighting circuit ?

 

[La Poste]

That's brilliant for a Tester that's not supposed to light up below 100v, think i'll stick to my MK tester. :lol:

What tester do you have?
Do you have a link?
Cheers.

 

[Specialist]

What tester do you have?
Do you have a link?
Cheers.

It's the MK LN6090 the 1 with the sensitivity control, sorry mate: have'nt got a link but try the TLC website or Test-Meter.co.uk might do them. It's the only 1 i've found so far that does'nt pick up on ghost voltages.

 

[BrightSparkPaul]

That's brilliant for a Tester that's not supposed to light up below 100v, think i'll stick to my MK tester. What was the result of your insulation test on the upstairs lighting circuit ?

It's my first job when I return there on Friday. It's been great to get some ideas from everyone, thanks for he heads up. Will post what happens in this thread on Friday.

 

[a1guvner]

It's the MK LN6090 the 1 with the sensitivity control, sorry mate: have'nt got a link but try the TLC website or Test-Meter.co.uk might do them. It's the only 1 i've found so far that does'nt pick up on ghost voltages.

Fluke Ldv2 is a good little tool

 

[MarkieSparkie]

It's the MK LN6090 the 1 with the sensitivity control, sorry mate: have'nt got a link but try the TLC website or Test-Meter.co.uk might do them. It's the only 1 i've found so far that does'nt pick up on ghost voltages.

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

 

[Golden_Boy]

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.

Where is this voltage being measured and with respect to where? A voltage cannot just be "there" its got to be measured between two points , It is after all A POTENTIAL DIFFRENCE.

 

[BrightSparkPaul]

Where is this voltage being measured and with respect to where? A voltage cannot just be "there" its got to be measured between two points , It is after all A POTENTIAL DIFFRENCE.

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?