50v on CPC on front plate.

danspark12345 · 2025-01-14T13:06:08+0000

So, I'm stuck.

There is a metal light switch, which has a noticeable vibration to it when you touch. Like a humming on your finger.

It is a 2 way at the bottom of the stairs. The 50V is only present when the lights are switched on. I tried changing the switch, no effect.

I haven't a clue! What it could be.

newfutile · 2025-01-14T13:17:14+0000

Your earth/cpc is not connected to earth correctly.
The test you did should show 230 volts.
Test from switch earth to a proper earth ie a socket screw

James · 2025-01-14T18:19:33+0000

There are a couple of things that could be wrong.
It may be that you are measuring an induced voltage on an otherwise dead leg of the strappers .
It could be a faulty switch with a large voltage drop across the contacts.

danspark12345 · 2025-01-14T21:38:44+0000

newfutile said:
Your earth/cpc is not connected to earth correctly.
The test you did should show 230 volts.
Test from switch earth to a proper earth ie a socket screw

Thanks,

How is the cpc not connected properly?

brianmoooore · 2025-01-14T22:27:40+0000

The earth wire is connected at the switch OK, but that does not mean that the earth wire is connected all the way back to the fusebox. It probably goes through several joints on the way, and it's likely that one of these has come adrift.

danspark12345 · 2025-01-15T02:17:38+0000

brianmoooore said:
The earth wire is connected at the switch OK, but that does not mean that the earth wire is connected all the way back to the fusebox. It probably goes through several joints on the way, and it's likely that one of these has come adrift.

Ah okay, so continuity needs testing

brianmoooore · 2025-01-15T10:26:02+0000

James said:
It may be that you are measuring an induced voltage on an otherwise dead leg of the strappers .

James makes an important point here. Did you measure the voltage on the blue wire as well as the yellow? If the blue is the strapper in use, and measures 230V, then a random induced voltage on the yellow, when measured with a high impedance meter, would be normal and expected.