| I was rooting around under the floor yesterday, sorting out some of the
| previous owners' disasters in the wiring department. At one point, I
| happened to grab a 5A cable, and at the same time touched a 15mm pipe
| carrying the mains water, with the back of the same hand. Pooffff... I
| ended up the other side of the room with a very wobbly arm!!
| Turns out, there was mouse damage on the cable which had exposed live
| copper (outer casing and red insulation had been chewed through).
| My question is this. Assuming I made a Live -> Earth circuit when I
| touched the cable and pipe, why didn't the 100MA trip RCD on the
| consumer unit trip? Could it be that the earthing is inadequate on the
| under-floor copper?
Why did the RCD not trip? I would expect that there could be several reasons
- the current flow did not reach 100mA so the RCD did not "see" the fault
- the RCD may itself be faulty - has it been tested recently?
- remember that an RCD does not know in any sense where the residual current
goes, it only know
that there is an imbalance (in this case >100mA) in the phase / netural
currents. It could be
that the earthing is inadequate, but this failure to trip is not the determinant
of that. I
suggest that you measure the earth loop impdence of the circuits in question, to
whether the earthing is adequate.
- consider turning off supplies not essential to your work in restricted areas.
lucky - how would anyone get to you if you had had a more serious shock?