You'll like this...

[dingbat]

Client calls to say the gas fitter reckons there is something afoot with regards to polarity of an installation. Occupant has also reported getting a shock from the radiator in the bathroom...

Quick live polarity check, all circuits on, does indeed suggest reversed polarity on supply. DB isolated and polarity is correct. Hmmm? Now where is that earthing conductor actually going? It's going nowhere; just pushed behind some panelling.

Turns out there's a phase-to-earth fault on the upstairs lights, but as there is no effective means of earthing this fault does not clear. Worse though, because of the presence of main bonding, not only do the exposed parts of all circuits become live, so do all bonded conductive parts. Now, if these parts were actually extraneous there would be an earth fault path, but as there is a lot of plastic pipe no such path exists.

And, if you follow this, there is as good a reason as any to test before you bond!

 

[securespark]

That is like a fault I was called to look at. Reverse polarity on boiler (presumably everything else too) caused by fault on two way lighting switches. When switches in one position the polarity was OK, in the other, it ws reversed..

 

[Adam_151]

Another interesting one is an open circuit neutral (borrowed neutral from the load side of an isolator on a different circuit, submain, etc) with a load present, appears on those plug in testers as phase/cpc reversal (as both phase and neutral go upto the same potenial and there is 240 between this and the cpc, it figures that phase and cpc must be swapped to make neutral the same potential as phase and 240 between neutral and earth!, its not clever enough to realise that phase is still phase and cpc is still cpc and its only the neutral thats moved!)