Discuss L-N Reverse and 240v on gas pipe in the UK Electrical Forum area at ElectriciansForums.net
The the look of it, plasterers float. It was at a socket where a plasterer has been working. Grommets in the back box so it’s all I can think only would be.Was it caught by a screw/nail? Or just a lack of grommet?
Yep,new rcd working correctly now too. ????Was it caught by a screw/nail? Or just a lack of grommet?
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Hopefully new RCD, short fixed and all happy once more!
It was a dead short live to earth.So what exactly was happening when that faulty circuit was energised? Was the MET swinging up to 230V and the gas pipe remaining at true earth? If all the earthing and bonding is OK elsewhere, it would also have been connected to a Ze of 48 ohms and dumping 5A into the ground. If it wasn't a solid short (hard to tell from your '0.00', which if it meant megohms, could still be 10k.) then why was it having such a marked effect at the MET?
What I'm getting at is that it's nice to find a fault, but unless one can prove that it was directly responsible for the symptoms, there could be more to find.
0.00 reading on the mft.What was the actual resistance, or did you see the conductors physically welded together?
These were IR readings.It looks more like a nail than float damage. If so, until you released it, the nail could have had an affect on your readings. As Lucien asks, we’re you continuity or IR testing?
0.00 reading on the mft.
These were IR readings.
I did state in the photo I posted that it was 0.00 IR between L/E.0.00 what? Megohms on an IR test? If so, that can still be 10kΩ which is more consistent with a carbonised insulation fault and is far from being a dead short, and shouldn't have much impact on the system elsewhere. If it's 0.0Ω (which you can't tell from an IR test, needs to be low ohms) then the only reason you were able to close the breaker was that the entire earthing system throughout the installation became fully live WRT real earth. Anywhere in the middle, the fault would have got much hotter.
In my original post I stated that I had end to end continuity on L N & E. So now I’ve seen the damaged cable, that to me that would suggest that the live and earth are touching together/fused together, however you choose to name it. That was the baffling thing,I had continuity of the ring. When I got to the job,I didn’t have a lot of spare time. I knew I had to go back and replace the RCD anyway which was faulty. So I disconnected the circuit which was causing the gas pipe to become live, leaving the site safer than when I arrived.MFT's have a variety of different ranges so just staying 0.00 could be ohms, megohms, volts, amps, milliamps, seconds.
An electrician should understand the need to, and be able to, quote the units as well as the measurement for the measurement to actually mean anything at all.
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Then you haven't measured a dead short, you have measured 0.00 megohms which could be many thousands of ohms.
Depending on your exact tester if you had switched your tester to the normal resistance range it may have given a result suggesting that it was open circuit.
the circuit which was causing the gas pipe to become live
230V between gas pipe and MET could be either way round -
Reply to L-N Reverse and 240v on gas pipe in the UK Electrical Forum area at ElectriciansForums.net
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