A puzzler

[securespark]

This story comes from a colleague...

A Gas engineer reported that pipework in the bathroom of a property was showing live with his voltstick.

I went along to check with a colleague, neither of our voltsticks showed any kind of voltage present on the pipework.

The power circuits were protected by a 30 mA RCD and a soft ELI test proved to be OK (can't remember the reading), MEB was in place and a ELI test from a nearby socket using the L&N of the socket and the earth wire from the Alphatek clamped onto the pipework again gave a satisfactory ELI reading.

We were about to dismiss the gas engineers report of live pipework when the central heating pump kicked in, immediately the voltstick glowed constantly indicating the presence of voltage on the pipework. It even indicated voltage on some plastic pipe feeding the hot & cold water to the wash hand basin in the bathroom.

As soon as the pump was switched off the voltage dissapeared. In an attempt to measure the voltage we used the test lamps between the electrical earth on a socket and the pipework, no voltage was indicated and the test lamps measure from 12v upwards, unfortunately we did not have a Fluke meter to measure a lower voltage. Whilst attempting to measure the voltage we inadvertently connected the test lamp between live and the pipework and the RCD tripped immediately.

My question is how can this be??? I guessed that the CH water and inhibitor was forming some kind of electrolyte in the system and as the water started to be agitated by the pump it was generating a voltage between the iron filings that collect in the CH water (Cathodic reaction I believe this is called or something like that), but I am at a loss to explain how this affected the H&C feed to the basin. I managed to offer an explanation to the customer and assured him that the electrical tests we had carried out proved that his system was safe.

I contacted the electrical technical guy who could not offer a solution but gave me a contact name and number of a technical guy on the gas side, he could offer no solution either.

Anybody shed any light?

My initial reaction is not to trust a volt stick, but apart from that am a bit flummoxed.

 

[Adam_151]

Is the CH on the RCD?

thinking along the lines of earth fault with a resonable impediance to not flow any fuses, and the pipework and the bond is a parralel parth to the CPC

Tried a clamp meter on the bonding cable when the pump is running?

 

[securespark]

Unfortunately what you see written down is exactly what went on and these colleagues have not returned since this account was written.

 

[plugwash]

first thing to check would be if the central heating is on the RCD. failing that its a strange one, maybe its coming from signal wiring or something.

 

[supersparky]

ive got one that beeps at a wall

it beeps in my pocket whilst im walking along if wearing shorts (good line that with the ladies )

they are very sensitive, static i would imagine

you will notice that if you run it past a row of MCBS on a split load board and then balck until it goes off, as you go past the RCD it will go off, the emitions from this go further due to the coil

i would say the explanation of static being caused by particles in the system would be the one

cant beleve anyone would go to so much bother- Its a voltstick - nuff said

 

[Lectrician]

My first thought would be to check the actual Ze (disconnecting all parallel paths) - could be a lost neutral on a well bonded install - this can give the oddest of faults which can remain untouches for years.

I would also check the polarity - I know an EFL was done, but some of these new testers have the option to automatically correct the leads if a reverse polarity is detected - this doesn't comply to BSEN, and should be turned of when the tester is sold as new.

 

[securespark]

can't believe anyone would go to so much bother- Its a voltstick - nuff said

Well, the report by the engineer that his voltstick lit up against pipework had to be investigated, naturally - it could not go ignored...

 

[JohnD]

ive got one that beeps at a wall it beeps in my pocket whilst im walking along if wearing shorts (good line that with the ladies )

My daughter carries a Live Wire and Stud Detector when she goes clubbing

 

[Pensdown]

ive got one that beeps at a wall it beeps in my pocket whilst im walking along if wearing shorts (good line that with the ladies )

My daughter carries a Live Wire and Stud Detector when she goes clubbing

I thought you found the "live wire" with your Stud Detector....my wife did

 

[Lectrician]

Any outcome, or just a dead end?

 

[securespark]

Well, as I said earlier, nobody has been back to the property since. No-one in our company can offer a logical explanation for what's happened.

That's why I'm posting here, to see if any of the DIYnot crew can offer any ideas...

 

[Adam_151]

2glasseyes?

 

[sparky40]

Hello all , how about this as a theory, { i've been to see Stella Artios today ! } Maybe the water creates enough friction when being pumped to make your fluke voltstick glow. Maybe I should stick to stella !!!