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

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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!
 
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BrightSparkPaul said:
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!
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When you say tests are within limits, what tests have you done so far?
 
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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.
 
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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!
 
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BrightSparkPaul said:
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.
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Def do the IR, it will then be a matter of working through the circuit methodically (think of the big picture)
 
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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?
 
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BrightSparkPaul said:
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!
Click to expand...

God give me strength ....................gas plumbers
 
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malcolmsanford said:
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?
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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.
 
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Specialist said:
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.
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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......
 
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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.
 
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Specialist said:
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.
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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 !!
 
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BrightSparkPaul said:
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 !!
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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
 
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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.
 
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Specialist said:
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.
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The flukes and kew techs both seem to light up around 6v.....
 
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La Poste said:
What tester do you have?
Do you have a link?
Cheers.
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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.
 
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Specialist said:
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 ?
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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.
 
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Specialist said:
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.
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I have one too and can confirm that it's quite insensitive to phantom voltage, but it's not infallible.
 
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Specialist said:
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.
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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.
 
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Golden_Boy said:
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.
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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?
 
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BrightSparkPaul said:
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 !!
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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.
 
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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..
 
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MarkieSparkie said:
I have one too and can confirm that it's quite insensitive to phantom voltage, but it's not infallible.
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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.
 
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Edd said:
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..
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Been wondering about that, what sort of Gas fitter gives up his good working tester to a client.
 
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Specialist said:
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.
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I am the opinion that ALL non contact "meters" are a waste of space............
 
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BrightSparkPaul said:
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!
Click to expand...

BrightSparkPaul said:
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?
Click to expand...

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.
 
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Specialist said:
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.
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this is what i thought spesh when i first saw it.....more like 120V??.....so a dangerous potential for a start....
 
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Voltage on gas pipe to boiler - newly qualified question!!
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