how does a broken earth have volatge on it???

chrisreid186 · Jan 30, 2011

''I had an interesting fault the other week whilst checking that Class 1 metal socket fronts were earthed. Admittedly it would have been best to carry out whilst dead, however this was just a quick check for peace of mind after doing a different job at night. I found 50v between the metallic light switch front and the main earth terminal at the consumer unit. When the light switch was switched on there was 100v. Further examination showed that the CPC (Earth) to the light switch was disconnected in the ceiling rose. Tests of the earth at the rose proved ok, IR tests on the switch cable proved ok. Reconnection of the CPC (earth) eliminated the problem. All I can put this down to is induction from the live conductors to the CPC conductor. One to look out for though''

originally posted by
topcop999

can anyone please explain why this happens?
Is it down to induction ?

thanks chris

nickblake · Jan 30, 2011

Chris i think you may well have answered your own question

telectrix · Jan 30, 2011

bet he wouldn't have read the same with an AVO analogue meter!

diditrain · Jan 30, 2011

Had a lady tell me that she kept getting electric shocks off her light switches. Her husband had told her it was just static.
I tested from main earth terminal to faceplate screws and read 230v
When the fuse board cover was opened up you could see that the shower cable had melted against the lighting circuit

WDMDL · Jan 30, 2011

Was the lighting cpc not connected at the board then? Should have been a big bang, not shocks from switch plates!

Or had that happened and blown the lighting cpc to smithereens and the shower fuse replaced?

Simon.

mogga · Jan 30, 2011

eons n eons ago as an apprentice i was screwing a switch plate back using a paint tin opener and it glowed we found the fauld was gompressed cable Joist had been cut to accomodate cables but cut wider than board leaving floorboards resting on cables and broken earth 6mm twe next to the 1.m we traced was squished so much it was same depth as 1.5mm but 4times as wide opened sheath and found the copper strands al spread out