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Types of lighting circuit

Postby chrisparr » Sat Feb 02, 2008 4:46 pm

Hi all,

I know there are junction box lighting circuits and loop in (?) circuits, but was there ever a third type in common use?

I ask as I've just been looking at the wiring up in the loft and I'm a little confused. (I think) the house was built in 1971 and the wiring seems original. All the lights seem to have a wire coming in from the switch and one going out to what seems to be a common neutral for all the lights in a junction box. All the switches have the wire going out to the light and the live coming in, as well as what I am guesing is a live wire link to the next switch. It seems to be forming some sort of ring (I think).

All the wires are insulated single core and earth (I think that's the right term), and the earth isn't used in the circuit :!:

The lighting works, but I am thinking it should NOT be wired up like this, and it needs to be rewired (if only to include the earth).

Does the above sound familiar to anone?

Thanks in advance

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Postby kbrownie » Sat Feb 02, 2008 7:23 pm

Hi chrisparr,
Sounds like you have a junction box wiring circuit using single core cables instead of twin and earth. This type of wiring is not that common these days with twin & earth loop-in circuit being the prefered method.
But no earth! needs to be sorted out. The circuit will run okay but you need it earthing for safety reason.
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Postby sparx » Sat Feb 02, 2008 7:51 pm

Hi Chris, not in common use but was done in some properties in late 1960's, wiring looks like very thin meter tails?
We have some double insulated singles here for our overhead ceiling heating system put in around 1974, so was still available then.
not having an earth does limit your choice of light fittings to plastic or double insulated so a rewire would be worth considering,
most common wiring systems as you say are loop-in (3 plate) usually looped at light but also done by looping at switches, other older method which some of us still use is to take feed to large JB then run tw/e to each light and twin brown to each switch, all Lives together & all Neutrals together, with each sw connected to its light in JB, advantage is only ever one cable to connect at each point. Made much quicker / easier now with push fit connectors, and with requirements for thin stud walls needing screened cables shorter switch drops often.
regards SPARX
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Postby ericmark » Sat Feb 02, 2008 8:45 pm

I have read about the system you have but never seen it. according to reports it was a source of electrical interference because live and neutral were not run together. Radio's and TV's would get mains hum. Out of interest I wonder if you get mains hum when some lights are switched on?
Sorry to say I have seen it left to the electrician on how he wants to wire new properties and even large building firms do not use their own electricians so moving from a house built with a name on one estate to one with same name on another estate by same builders can have different electrical wiring. Biggest problem has been central heating where electricians have saved coppers by not using standard junction boxes and followed one of the three main plans Y, S, and C but invented one of their own. I like Sparx's method of wiring lights but never seen it done. Electrical firms are far too mean junction boxes (JB) cost too much and most new houses a wired to a price. Re-wires are completely different often the owner will then let electricians fit the best. The same with very expensive single houses not part of an estate. I say this in case you do go for re-wire. I'm glad Sparx answered first or I would have jumped in with both feet until I saw his reply I had forgot all about reports I think quite rare. I wonder if wiring will ever become listed? I would love to see it.

Postby chrisparr » Sun Feb 03, 2008 9:27 am

Many thanks for the answers.

The situation was further confused by a past owner putting in spotlights and wall lights into the bathroom using the junction box method (but modified slightly to work with this system).

I sat there in the loft for 20 minutes looking at the whole mess trying to work it out before I gave in and drew a diagram. The fact that all but 2 of the wires were black didn't help (continuity testers are a great invention).

A rewire it is I think.

I'm capable of doing it myslef (yes regs have changed), as I did electrical training when I was an apprentice instrument mechanic (before you try, I've heard every instrument mechanic joke an electrician can come up with), but its been about 13 years since I did any wiring so I may get someone in just in case there are any other original features waiting for me.

Thanks again,

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