lighting wiring

[Tom Hoyland]

Hi, Having moved into a new house we are naturally "making the place our own". We are replacing lamp fittings and switches as they are quite old (1980s we were told the house was reqired and they were fitted). However the wiring of the lights seems a little unusual. To the switch there are two 2-core cables - with red & green solid cores. One is the live supply the other obviously the switched. The green tests as earthed and are joined together in the wall box with a block. The fittings then have a single core neutral run to them either direct from the CU or spurred from other light.

I have not come across this way of wiring lightws before and wondered how unsual it is or was it standard some time ago?

Many thanks, Tom

[BigWallop]

The wiring sounds as though it may all have been done inside conduit to me.

To have two X two core cables with the colours you describe inside a light switch it sounds as though the sparks has run red as all the switched live wires and combined them with an earth conductor in case they terminated at a metal back box or face plate. Not unusual if the wiring is all inside conduit.

A common neutral, black, running to all the light fittings on the ceilings is not un-common and can also be left in place.

As long as none of the wiring is damaged or corroded, and it is all properly connected and earth bonded, then you shouldn't have any problems with it.

[Tom Hoyland]

The cable doesn't actually run in conduit - it is simply chased into the walls and plastered over. Generally it seems to be wired ok except for a floursecent strip light in the kitchen. Here i found the red + green 2core being used as live/neutral with the separate neutral fixed to the earthing point on the metal case! This has since come down and LV lighting put in.

Thanks, Tom

[BigWallop]

Can you see what material the cable is made from that goes to the switch ? Is it grey or white covered flat PVC cable with one single copper conductor for each colour ? Or is it flex with very thin strands of copper wire bunched together to make up thicker conductors ?

[aj]

Does the green core come out of the outer grey (?) sheath of the cable in bare copper and have a green sleeve fitted from there or is it insulated green going inside the outer sheath? If it is a bare copper core (earth) that has a green sleeving on it then the cabling you have sounds like single and earth domestic wiring (twin and earth without the neutral) which is not that uncommon to see in use but it is a little unusual for a whole lighting installation to be done in. There is nothing wrong with it's use although the flourescent fitting wiring you mentioned does not sound too good, I would suggest you check out the rest of the fittings as well.

If it is insulated in green going up inside the outer sheath I would suggest you get in an electrician to have a look because it is possible that it could be low voltage wiring which is a bit of a hazard on 240V.

AJ

[ARWadsworth]

There are red and earth cables that do have a green/yellow insulated pvc earth. It is/was available with both a red or grey outer sheath. I imagine that the cost of the cable was very high and hence it was rarely used.

As for wiring the lighting in singles, some councils insist on it when their properties are rewired or if they are giving a grant for a rewire.

Adam

[Lurch]

On Sun, 06 Jun 2004 01:25:21 GMT, "BigWallop" strung together this:

No, wrong again. It's all wired using 6241Y cables.

[Lurch]

On Sun, 06 Jun 2004 01:01:29 GMT, "Tom Hoyland" strung together this:

It was quite common some years back and is still used in some places today, although normally the 'loop-in' method is used. The cables you have are just twin and earth type cables without the black one. It's all a safe method and nothing wrong with it.

[Tom Hoyland]

Thanks,

It is grey flat two solid cores - one red sheath one all green sheath. Tom

[BigWallop]

Then it is 6241Y PVC cable that's been used for these circuits, as Lurch says, and is perfectly normal for the era your property was rewired. The wiring method used is one of many in the lighting circuit configuration schemes of the time, which used two of the 6241Y as thinner wiring to the light switches much more than the now more popular single 6242Y T&E cable with an extra red coloured over sleeve, or red tape, to cover the black.

It does the same job so is nothing to worry about unless you're thinking of putting a heavier load on to it and it needs to be thicker conductors.

[Christian McArdle]

This used to be common practice and is probably still legal. The neutral is looped directly to each fitting, whilst the lives follow a different path to the switches and on to the fitting. This method is now deprecated, as it leads to stray inductance causing hearing aids to malfunction when on "loop" function. There is no reason to remove it, though, if it causes you (and your neighbours) no problems.

The modern technique using T&E cabling with no loops (even on 2 way switching) eliminates the problems.

Christian.

[Lurch]

On Mon, 7 Jun 2004 09:49:57 +0100, "Christian McArdle" strung together this:

As I was writing my reply I was thinking to myself, I haven't seen Christians response regarding induction loop problems yet, but here it is!

[Christian McArdle]

I'm nothing if not predictable!

Christian.