I'm curious, coul someone explain this...

[murphaph]

Hi all, great forum.
Today I went to B&Q and bought 2 new wall lights and a pendant light. I took the old fittings down and did a straight swap (including new 2-gang switch as the old one was looking a bit tired). The lights are working fine, but I'd like to know what I did!

Ok, This setup must be very common, 2 wall lights either side of the fireplace and a pendant. There were 4 wires present at the pattress box behind the switches. I used a phase tester with all cores disconnected and alllight fittings removed, there was one live core out of the 4. The other three all appeared to be Switched live to the three fittings as there was 1 jumper wire from 1 switch to the other. At all three fittings there appeared to be 1 switched live and this is what I'm curious about; there were 2 cores wired to the neutrals of all three fittings. What's this all about?

My basic DIY book lists the two standard wiring types, junction box (what I think I have) and loop-in. I'd really appreciate being filled in on what's going on for future reference.

Sorry for the long post. Thanks all.

 

[plugwash]

seems like a job done with seperate single cores

were there any earths?

did the wires run in some kind of pipe?

did they have a grey sheath as well as the inner core insulation?

 

[murphaph]

seems like a job done with seperate single cores

Yeah, all single cores everywhere.

were there any earths?

None at the pattress box as it's plastic as was the switch (and replacement) or else the original installer did run an earth but not with green&yellow maybe? There is an earth at all 3 fittings (though for some reason the previous installation of pendant did not use the earth that was tucked away to one side. i decided to connect it to the earth strap from the new fitting. I assume I did no harm with that.

did the wires run in some kind of pipe?

Think they're all running in conduit but it's hard to see for sure.

did they have a grey sheath as well as the inner core insulation?

Yes. At the pattress box the 4 cores were as follows:
3 x Black inner insulation within grey sheath
1 x Red inner insulation within grey sheath

Does that help at all?

 

[plugwash]

seems a pretty strange install

on an install with singles its normal to use red for all lives

also the norm is to use either double insulated cable or conduit not both (though theres nothing wrong with using both)

was there just one earth at each box where there was one or was there more than one like with the neutrals and if there was more than one were they properly connected together in a terminal?

your install may be perfectly fine but its definately abnormal and it seems sensible to establish that its all been done safely.

 

[murphaph]

At the pendant, the earth was not in any choc-block, just two green&yellow cores twisted together and shoved up into the rose. Pretty poor looking. I'll jhave to double check the wall lights-they used bare conductor into chock-block along with the live and neutrals, can't recall seeing more than one bare conductor though.

Would I be correct in thinking that the neutrals are all looped together before returning to a junction box somewhere in the voidspace? It seems non-standard to do this but I assume it would work, even though it's a messy way of doing it (it would save using junction boxes and as this house was built in 1980's Dublin, which was a rather bleak time for the building trade here, it wouldn't surprise me that this was the reason, especially given some of the other shody work I've found over the years)

Well, I figured it all out. There are no junction boxes in the wiring. The permanent live is carried from the CU to the back of each switch in a daisy chain. All neutrals are connected in the same daisy chain style back to the CU. All single core throughout. It's been like this for 20+ years without burning the house down, I'm assuming it's ok, is it?

 

[plugwash]

theres nothing wrong with the wiring arangement for the live and neutral its just the earthing i'm a little worried about. ie do those earth wires actually go back to the CU and are the connections between them decent you mentioned twiseted wires which is a right no-no

also if you don't have an earth at the switches you should use screwcaps to make sure there is no exposed metal (ideally you should put an earth in but thats major disruption)

 

[murphaph]

The earths at all the fittings do go back to the CU earth strip, I ohmed them out. I am going to fit screwcaps in any case, for aesthetics but I can appreciate the need for them 'just in case'. It's a bit of a shame about no earths though, I quite liked the look of a polished aluminium switch I saw, but I couldn't be arsed adding earths for that!

Thanks for all your help