Older style lighting wiring

[MarkyBoy666]

I was just wondering if anyone could help with a small query. My first floor lighting circuit which runs through my loft, is an older style one, with red, black and green wires within metallic conduits instead of an outer sheath. The 'junction boxes' are also metallic with metallic 'lids' that are screwed on and kind of swivel open and shut, and within which there are no terminals, but duplicate red/black/green wires that branch off to the light fitting, and are presumably connected to the main ring wires at some other point in the circuit.

What I was wondering was, could someone tell me what this older type of junction box/circuit is generally referred to as, and what I would need to type into a search engine in order to get specific tips on running an extra spur from such an existing circuit?

Many thanks if anyone can help!

 

[Adam_151]

Sounds like steel conduit: http://www.tlc-direct.co.uk/Main_Index/Conduit_Steel_Index/20mm_Galv_Conduit_and_Fittings/index.html

 

[MarkyBoy666]

Thanks Adam, that looks like the baby (except that one looks a bit newer than the one I inherited when I bought my house!) That gives me something to work from, I definitely need to look into this a bit more before running a new loft light from it because it doesn't look as though it's quite as straightforward running a spur from these - due to lack of available wire and no obvious way of inserting a modern junction box.

Thanks once again!

 

[slippyr4]

Consider carefully whether you really want to extend that wiring- it's old and possibly past it's useful working life.

If it's "loop in" wiring, which is probably is, then your supply runs from one light fitting to the next, to the next, and the last light fitting (whichever that may be) will only have one supply cable.

You can easily extend the loop from that point, and it would be fine to use a modern sheathed twin and earth cable, clipped to joists and rafters etc, for the loft light.

See the sticky at the top of this forum for explanations of loop in wiring.

 

[ban-all-sheds]

red, black and green wires within metallic conduits

Consider yourself lucky that there's an earth conductor - often the conduit was used as the earth which makes adding/changing it kinda tricky.

But you should get it all inspected - it does sound like it's getting on a bit. I'd not be surprised if the sleeving was rubber rather than PVC...

 

[MarkyBoy666]

Thanks guys, much appreciated. I wasn't planning on rushing into anything here, and may end up taking advice on it from an electrician if I think it's too old as to be safe.

Just one quick question...I knew about the metal sheathings often being used as earth, but I take it I can assume that the green wire present must be an earth wire in this case?

 

[ban-all-sheds]

You can assume that that is what it is intended for.

You cannot assume that it is actually doing the job - you have to test.