Voltage leak

[bramley4600]

Recently got one of these British Gas contracts to cover my combi boiler - 2 years on the run it failed on Christmas day morning !
They also come out and check/service the boiler before they accept you.
The combi is in the loft (live in a bungalow) and when the engineer came out he had one of these wand things that he wafted around and as soon as he approached the boiler it lit up red.
Straight away he said he could not touch the boiler. Did the same when he touched the loft insulation around the boiler and even the wooden roof struts.
He then got his multimeter out and showed that there was a 'stray' voltage of 24 volts.
Even did it with the power to the boiler turned off.
Got an electrician in and he found the same but could not isolate the problem.
So, now have a boiler I can't service and a problem with the electrics that can't be solved.
I'm not a spark but there are lots of cables, both ring main and lighting around the pipes near the boiler - unavoidable because of the layout of the bungalow.
Any ideas about what I can do now.
Thanks for any help.

 

[conny]

Not a spark so this is just speculative. Not sure what this 'wand' is, sounds like a detector for tracing cables in walls or something. If it is 24v what is he measuring this voltage across? Is it between the boiler casing and one of the cables or between the casing and the loft insulation?
Do you have damp or condensation in the loft? Do you have any electrical problems elsewhere in the house?

I would suggest you get another electrician out with the job of finding where this fault is. If the boiler engineer won't touch the boiler then it would suggest this is where the fauly may be and surely he should be competent at finding/repairing it.

 

[bramley4600]

Thanks Conny.
I think he measured the voltage across the boiler casing and the water pipes.
The loft is dry. Interesting that you asked if there was any damp. There is a flue at the side of the boiler which vents the shower. It came loose last year and must have let some rain in but it looks very dry. The electrician said he saw no damp. No other electrical problems in the house that I know of. Got a new Consumer Unit last year and it trips at the slightest thing.
The wand thing is a Voltfinder/Flashlight from Klas Ohlssen (bought the same one myself, looks like a fat pencil).
To be fair to the British Gas guy, he only came to service/check the boiler and it wasn't his job to find the fault, although he was very helpful.
A few have suggested that it could be an induced voltage as the electric cables and the water/gas pipes are all over the place in the loft.
If it was an electrical fault, would it not show 240 volts instead of 24?

Cheers

 

[AndyPRK]

Some guessing.

You could turn off each MCB in turn and see if the voltage disappears.
E. g lights MCB then sockets MCB. Or even the whole CU.

And check the gas and water pipes where they enter the building are bonded with green/yellow wire.

 

[bramley4600]

Thanks Andy.
I will try it tomorrow.
The bonding is OK, checked both the Gas and Water. The spark suggested there should also be bonding between the pipes as they enter the combi boiler but that it was not absolutely necessary adn did not help to isolate the problem.

Cheers

 

[Taylortwocities]

The spark suggested there should also be bonding between the pipes as they enter the combi boiler but that it was not absolutely necessary adn did not help to isolate the problem.

Get your "spark" to follow the pipes up into the base of teh boiler. He/she will find that all of the pipes are terminated in a great big metal plate at the base of the boiler. So additional bonding is not needed, has never been needed, and pointless.

 

[JohnW2]

Get your "spark" to follow the pipes up into the base of teh boiler. He/she will find that all of the pipes are terminated in a great big metal plate at the base of the boiler. So additional bonding is not needed, has never been needed, and pointless.

Indeed - probably the only possible theoretical 'catch' that could be cited by quibblers being PTFE tape.

However, even if the pipe manifold were made out of some super-heat-resistant plastic (or the pipes were, miraculously, effectively insulated from a metal one by aforementioned tape), I think it would probably still be difficult to field a convincing argument as to why cross-bonding was needed.

Kind Regards, John

 

[mfarrow]

If everything is bonded together, the circuit has a good earth, and the pipes make a good and proper connection into the boiler, then all should be at the same potential.

I very much doubt that your casing is 'live', however there is a risk that the appliance lacks fault protection and therefore this should be sorted soon. Did your electrician check the boiler electrical connection for an earth? Did he check the voltage between that and the pipework, and test the loop impedance of the supply?

 

[bramley4600]

Thanks taylor, john and mfarrow for your replies.
I'm not sure what checks the Gas engineer carried out. He helped as much as he could and did far more than he should have done, his job was to service the boiler at the end of the day and not find faults with the electrics.
Seems like I will have to get another electrician.
Find it so depressing trying to find plumbers, electricians round here. Can't tell you how many phone calls I have made to get them to do a job. Umpteen plumbers have promised to come round - nothing. Rang an electrician on Monday said he would come round - nothing. Several of them have been honest and told me that it's just not worth their time and effort doing small jobs. Then they wonder why people try to do jobs themselves.
That's off my chest now.

Thanks again guys for your help. Will get up in the loft this weekend with my multimeter and wand thingy and try some of your suggestions.

Cheers