Hi guys,
I was just replacing my light switches in my new flat (like for like, just a different look) when I came across a issue with the living room one. I had just swapped the kitchen one, switched power on to test it. Before I touched it with my hand I put my my screw driver on the metal cover (I have one of those ones those with a mains tester built in) just to play it safe. Since the living room switch is right next to the kitchen one I ended up touching it as well with the screw driver.
I was surprised to see that it lit up a bit. So I put my meter on the chassi and into a neutral source on a nearby wall socket. I had 44V coming from it. I isolated the power and took the cover off. Everything seems fine behind it (no damaged cables), the pattress box (metal) was earthed correctly which the faceplate then connects to in order to earth it.
So I did a bit of testing, and I found that I get the following,
44V if lights (a dimmer) is on between earth and neutral
32V if lights are off between earth and neutral
10-12V if I disconnect the dimmer completely (L and O just hanging loose) and measure between earth and neutral
So I seem to have a earth leak somewhere. But here is where it gets strange, if I disconnect the earth from the pattress box, I then get the following,
0V from the pattress box to neutral
0V from the earth wire to neutral
Why is that? I get 0V as soon as the two are not connected to each other. But as soon as I connect them I get around 12V again.
As I said I cant see any damage to any wires or anything touching something it shouldnt. The pattress box is in a brick wall so I can't verify if there is something touching it from the back. But what would cause this voltage to just appear when the pattress box is earthed? I would expect to see this 12V coming from either the earth wire or the pattress box?
I was just replacing my light switches in my new flat (like for like, just a different look) when I came across a issue with the living room one. I had just swapped the kitchen one, switched power on to test it. Before I touched it with my hand I put my my screw driver on the metal cover (I have one of those ones those with a mains tester built in) just to play it safe. Since the living room switch is right next to the kitchen one I ended up touching it as well with the screw driver.
I was surprised to see that it lit up a bit. So I put my meter on the chassi and into a neutral source on a nearby wall socket. I had 44V coming from it. I isolated the power and took the cover off. Everything seems fine behind it (no damaged cables), the pattress box (metal) was earthed correctly which the faceplate then connects to in order to earth it.
So I did a bit of testing, and I found that I get the following,
44V if lights (a dimmer) is on between earth and neutral
32V if lights are off between earth and neutral
10-12V if I disconnect the dimmer completely (L and O just hanging loose) and measure between earth and neutral
So I seem to have a earth leak somewhere. But here is where it gets strange, if I disconnect the earth from the pattress box, I then get the following,
0V from the pattress box to neutral
0V from the earth wire to neutral
Why is that? I get 0V as soon as the two are not connected to each other. But as soon as I connect them I get around 12V again.
As I said I cant see any damage to any wires or anything touching something it shouldnt. The pattress box is in a brick wall so I can't verify if there is something touching it from the back. But what would cause this voltage to just appear when the pattress box is earthed? I would expect to see this 12V coming from either the earth wire or the pattress box?
