Doing some redecorating work in a room at a friend's house, and as part of this I swapped the old cheap plastic light switch out for a nice new metal face one. I then got a complaint that they got an electric shock off the plate part of the switch. Testing it with a test screwdriver, I got a faint glow from the light. Took everything apart, and checked in more detail with my multimeter and found that the earth line to the switch had a potential of about 3V AC. Checking everything else in the room I found no faults, but that all of the earth lines in the lighting in the room were at the same 3V potential.
Checking elsewhere, I found an unidentified and loose bare wire in a ceiling rose on the landing just outside the room. All the other earth wires I've seen in the place have proper green & yellow sheath on them, but this one was just taped up in a bit of white tape. Checking with my multimeter showed it was continous with the earth lines that were at 3V, but that it had a resistance of about 28 ohms which seems a little odd. Nevertheless, I connected it up to the other earth lines in the rose and that seems to have resolved the problem.
My questions:
- was I right to connect it up like this?
- I presume the 3V was just because the earth line runs along side a live and because it was unconnected it was picking up an induced current; does that sound right?
- why would it have such a high resistance?
- does the owner urgently need to get an electrician in to check this? (she's reluctant to spend the money, and figures that as it must have been like this for years can't be a serious problem that needs urgent attention)
Checking elsewhere, I found an unidentified and loose bare wire in a ceiling rose on the landing just outside the room. All the other earth wires I've seen in the place have proper green & yellow sheath on them, but this one was just taped up in a bit of white tape. Checking with my multimeter showed it was continous with the earth lines that were at 3V, but that it had a resistance of about 28 ohms which seems a little odd. Nevertheless, I connected it up to the other earth lines in the rose and that seems to have resolved the problem.
My questions:
- was I right to connect it up like this?
- I presume the 3V was just because the earth line runs along side a live and because it was unconnected it was picking up an induced current; does that sound right?
- why would it have such a high resistance?
- does the owner urgently need to get an electrician in to check this? (she's reluctant to spend the money, and figures that as it must have been like this for years can't be a serious problem that needs urgent attention)
