weird ceiling lighting voltage?

[Jim]

hi- doing up an old house.

It will be completely rewired by an electrician, however, I'm trying to get some lighting working first to help in clearing out the place.

One room had 2 non-working fluorescent lights which I removed, leaving

2 cables coming in through the ceiling.

I connected simple light fittings (bayonet style bulbs), which do not work.

I've measured the voltage across each of them, and it appears to be 1.4 volts. Measuring the working light fitting in the next room gives 240v as I'd expect.

Can someone explain this? Might there be some kind of step-down transformer hidden in the ceiling?

[Tim Morley]

Did you also measure both cables to an earth connection? Could be a disconnected neutral at the other end?

[meow2222]

no. you might have connected between earth and neutral. The fact that one's red doesnt stop it from being miswired.

NT

[Jim]

Hi-

I thought I'd let people know how things worked out.

As it happens, meow2 was right - the cables just appeared to be miswired. What had confused me is the 3 cables from each ceiling point comprised of 2 covered in plastic (one red, one black), and a 3rd bare cable.

I had automatically assumed that the bare cable would be the earth, with the red and black being the L and N.

Turns out the red was Live, the *bare* cable was N. Now lights work from the walls.

Thanks people !

And just to let people know - the whole house *is* going to be rewired shortly. Just trying to get some temp light to help in the meantime.

[Dave Plowman (News)]

How did you check this? Thing is that the neutral should be (near enough) at earth potential so connecting to the earth instead will make the light 'work'. Not the right way of doing it, though.

[Lurch]

On or around 8 Nov 2005 01:00:19 -0800, "Jim" mused:

I really wish you hadn't.

You really are dangerous. Chances are, the bare wire is earth and the neutral is disconnected somewhere else but as the earth will most probably be connected to neutral at the service head, and you've probably got no RCD, you are now using the earth as a neutral.

Well done, consider yourself a complete moron.

[Jim]

Lurch - it works. the light lights. We can clean up properly now.

As I said... it is going to be rewired.

[Lurch]

On or around 12 Nov 2005 13:10:47 -0800, "Jim" mused:

Great, ignore the lethal way in which it works then.

[Christian McArdle]

Don't touch anything metal in the house now. Anything earthed is now connected to live via the light bulb. If the earth gets disconnected, or has a high impedence (i.e. TT with failed RCD), then anything earthed, such as your radiators or bath will become live.

I would consider your solution to be of the "immediate danger" category. I would not allow my family to enter the house. A better short term solution is to disconnect the light fitting and use a table lamp.

Christian.

[Christian McArdle]

Whoops. Sorry about the late post, my newsreader dumped me back into the distant past without me noticing!

Christian.