House lighting radial wiring question

[Roger R]

The work is to modify the lighting arrangements in a friends living room. At present there are four wall lights and the plan is to remove these and at each location extend the wiring down the wall (recessed) to a new socket (round pin) just above the skirting for some free standing lamps.

I thought this would be peice of cake, I've just rewired my own house - until I took the fittings off and saw the wiring arrangements.

The house was built around 1984. There is a conventional, if old, Wylex consumer unit. Ring main and power radial circuit cables are conventional twin and earth (grey outer-old style) A photo of the interior of the box with cables and some diagrams may be seen here:

lighting circuit is something I had not encountered before. it is not the conventional loopin system -or ISTM, the radial alternative. The cables are all single, grey outer. Line (phase) red core plus earth conductor, Neutral being single core black,

The lighting circuit is on one fuse. There are two line cables and two neutral cables heading off, presumably a pair for each floor.

The arrangement appears to be that the line conductor is looped to each switch in turn. The neutral cables are looped to each light fitting in turn. A single cable (red inner) links each switch to its light fitting.

So at each switch there are three single red wires and at each lamp fitting there are two blacks and a red. see diagram.

Presumably this arrangement makes for economy of cable. I believe there are no hidden joint boxes anywhere (but I could be wrong..)

Question is...how to go about this job? (hopefully with access from the floor above) Can this type of single core cable still be obtained? I somehow doubt it. So should the whole existing lighting circuit be replaced with a loop in arrangement using twin and earth? As the modifications required are only on the ground floor could this be replaced with loop in and the upper floor be left as it is?

Please advise.

Roger R

[Christian McArdle]

Yes, although this arrangement is now deprecated as it interferes with hearing aids and might even have implications under the disability discrimination act.

No need. At the existing light locations, drop a 1mm T&E down to the socket and wire it up as if it is was the existing light fitting. As you will need to bury these joins under plaster, you should crimp the connections (and probably solder the crimps for good measure!), heat shrink the connections, then heat shrink the entire bundle. Then bury in plaster (after testing, of course).

That's an alternative, although a little overboard, especially if hearing aids aren't used, or you have no 'loop' audio appliances.

Christian.

[tinnews]

Yes, I have a reel of it bought a year or so ago at my local electrical wholesaler. Most wholesalers will stock it or get it to order I should think.

[Andy Wade]

Not the question you asked (which Christian has answered fully), but should you/they ever be temped to separate this into two circuits (upstairs and downstairs) be very careful you don't create a 'borrowed neutral' situation where one or more lamps gets live from one circuit and neutral from the other. With the wiring system in question it's highly likely that 2-way switched sub-circuits for the stairs and landing lights take their live feed from one half and return the neutral to the other. If this is the case it means you can't do the split without re-wring the hall/landing lights.

And what's that piece of flex doing connected to the lighting fuse?

[Roger R]

Thanks, and to Christian and tinnews too. Well the news was better than I'd hoped.

You make a good point about the 2 way hall /landing neutral return. I believe this is exactly what happens in this case, the landing light is fed from downstairs but its neutral returns to the upstairs circuit.

It did cross my mind that I could split the lighting if I replaced the dated wire fuse CU with a new unit, as the existing six circuits is a bit limited.

But I'm in two minds about replacing the CU as (perhaps surprisingly) I havn't looked in the outside meter cupboard to see if there is any switch there or if the meter tails can be easily disconnected without calling out the board for a tempory disconnection. As an interim measure I have obtained Wylex MCB replacements for the existing wire fuses.

Re: Piece of flex. Feeds an old burgular alarm, fitted by alarm co. for original owner. (That alarm now deactivated but I leave that there because the bodge makes a matching set with the piece of bicycle inner tube bypassing the gas meter ;-)

Roger R

[Andy Wade]

Enough said! - but seriously, best to remove it if it's no longer doing anything.