Had a rather strange occurrence today. Was working away (me plus 2 other lads) finishing off a social housing rewire (just like every other day) ; I completed the board change and connected the tails. Switched on the DNO isolator and proceeded to carry out Ze and pfc tests. All ok thus far. flicked rcd's on and pressed buttons to functional test. Then started testing trip times ready for cover going on board. The timing of what happened next was crucial. At one of the point were I turned an rcd back on, one of the others lads was 2nd fixing a light switch. Stripping the cable and happened to be holding line and earth...
He got a belt. Naturally, started having a pop at me. To which my response was 'All the breakers are off, WTF!!!'. Quickly turned everything off and first thing that popped into my mind was the tails must be wrong way round (didn't know it was line that was live at this point, but then thought 'can't be as the tester would have flagged it as reverse polarity on Ze test'. Anyways, a few minutes of testing and diagnosing how this could happen and a fair bit of head scratching, turns out the MCB for the lighting, although it was in the off position, was letting current past. All the others seemed ok, To be honest, this is not something I normally test.
So, be aware, such things CAN happen.
He got a belt. Naturally, started having a pop at me. To which my response was 'All the breakers are off, WTF!!!'. Quickly turned everything off and first thing that popped into my mind was the tails must be wrong way round (didn't know it was line that was live at this point, but then thought 'can't be as the tester would have flagged it as reverse polarity on Ze test'. Anyways, a few minutes of testing and diagnosing how this could happen and a fair bit of head scratching, turns out the MCB for the lighting, although it was in the off position, was letting current past. All the others seemed ok, To be honest, this is not something I normally test.
So, be aware, such things CAN happen.