Dodgy bathroom light wiring

[Lobster]

I just found myself having to reattach a bathroom light fitting to the ceiling (which, following a failed fat roof, was reboarded and replastered yesterday by someone who can do it better than me, ie properly!).

Although the light worked fine beforehand, I can't quite get my head round it - just for my peace of mind, can someone explain it to me s-l-o-w-l-y?

There were originally two incoming T&E cables; one was the circuit feed, the other the switch cable - so far so good. However, the two lives were patched together in a terminal block, and the two neutrals were connected to the lightbulb in the (metal) ceiling fitting. The earth cables were just twisted together, unsheathed, and stuffed into the ceiling void; and not connected to the earth clamp on the light fitting.

Was this arrangement as potentially lethal as I think it was (especially given that the ceiling void was recently full of rainwater...?

Thanks David

[John Rumm]

I take it when you say the neutrals were connected to the light bulb you mean one to each terminal rather than both actually connected to each other?

Well, the earths ought to have been sleeved and connected to the metal fitting, in addition to being connected to each other. The black wire returning from the switch ought to have had a red sleeve or tape on it to indicate that it was really a live. So in essence it was a lash up.

The risk would depend on how much exposed metalwork there was on the fitting, and how easy it was to come into contact with it. For there to be a shock hazard you would also have to pre assume a situation where water entered said fitting and formed a circuit between the live and the metalwork.

Is the lighting circuit fed via a RCD?

[John Rumm]

The switch should always be in the live. From your description with the two lives connected together - but not connected to the fitting, then it sounds like all power to the fitting had to come via the switch (i.e. down to the switch via the red wire, and back via the black).

So what was there, sounds like it was "correct" in the sense of how the circuit was wired - even of the workmanship or attention to detail was lacking.

Your main shock hazard would be from a combination of a ceiling full of water, and someone fondling the metal on the fitting. Even if the earth had been connected to the metal work, there is no guarentee that enough current would flow through the water to trip the MCB (a RCD would detect the leakage and trip), but hopefully the earth would limit the voltage that the metalwork could rise to.

[Lobster]

Yep, one neutral to each bulb terminal.

And all that's sorted now, with a mini-junction box. But previously wasn't the switch wired into the wrong wire, so that there is always power at the fitting? Or have I got that wrong, or is that not significant?

Fitting is one of those glass globes, with a metal plate attached to the ceiling (unlikely that it can be touched by someone standing in the bath, but possibly standing on the floor)

No.

Thanks David

[Dave Plowman (News)]

Apart from the earth issue, which is obvious to resolve, the wiring you've got with two blacks going to the fitting is pretty standard. One is indeed a neutral, the other the switch return, which should be sleeved in red to identify it. The other option is to use TW&E with two red cables for the switch circuit, but few do.

[ARWadsworth]

#

It may be worth checking the other fittings in the house are not wired up like the bathroom light. If they are then there is a chance there may be no earth or a poor earth at the bathroom fitting.

shows your bathroom light.

Adam

[Lurch]

On Mon, 16 Aug 2004 00:36:20 +0100, John Rumm strung together this:

Sounds more like the last fitting or a spur off of a standard loop-in lighting circuit.