The other thing that's good about junction boxes is that by by using a six way rather than the usual four way box you can conveniently provide switched circuits to two light fittings, and then use a 3&E switch drop cable (suitably colour sleeved of course.) This can be pushed to three lighting circuits, but does get a bit crowded in the junction box at that point, and needs one more core to the switch.
Charles F
Stop telling people how easy it is:-)))))))))
This group is a bit different to most people - the majority of the public still think that electrical work is complicated, illegal and unsafe to DIY. I don't think you will run out of work!
Charles F
>1920s, if not before, using '3-plate' ceiling roses. 'Plates' referred to the brass terminals for L, SL and N. No earth required in those days.
In message , Charles F writes
I'm in the process of doing that at the moment, there are 2 reasons, firstly I haven't decided where the lights are going to be so it would be difficult to wire everything via the roses. Secondly I can just take T&E to the roses and save on the number of wires in them. The latter will also stop people in the future asking on here what to do with all the wires they have hanging from the ceiling after they removed a rose.
They *could* be wired with 4 sq mm, then a radial is correctly protected with a 32A MCB.
This was common in the 1960's when there was no requirement to earth lighting circuits. Providing you don't have metal faced light switches or metal light fittings which should be earthed then the lack of earth connections on the lighting circuits doesn't present any hazard.
rossettes it is a red sheathed twin cable with a green stripe, inside the sheath is a bare solid earth and a red sheathed live. From the switches a s ingle grey sheathed switched live and Earth goes to the rosettes. The neutr al is again a single that simply goes from rosette to rosette and does not neccesarily follow the route of the main live feed.
but unlike ours is all done in T&E with the neutrals as well as the live l ooped in the switches. This does seem to result in a lot of wires in the ba ck boxes especially in twin ganged switches and those that involve two way switching. All the back boxes are 25mm deep as opposed to 16mm. The walls a re dry lined with 15mm PB so the 25mm boxes do not need sinking, the only a dvantage I can see to this method of wiring is that replacing the rosettes with light fittings is simpler since there is only a single T&E cable with a switched live and neutral.
That was the way it was done back then (when I was an apprentice) Easy to make a mistake in the wiring with all sorts of strange results in t he lighting.
The modern system has "routinised" lighting circuits so mistakes are less l ikely. Also fault finding/extending is easier. But more wire is used.
Junction boxes should only be used as a last resort for extending circuits, otherwise avoided. They are a common source of faults. No new installation should have them. Even back then they were avoided.
With loop in ceiling roses, you shouldn't need them even for extensions these days.
The problem is with this sort of thing is that there is stuff you may find and fix. But there may well be stuff you don't find (ie hidden)that might cause future problems. Some faults can't be detected with instruments, (ie only visually) Stuff buried in plaster, inside walls, under floors boards.
It's a problem near inductive loop hearing aid systems, because using singles is often done so the live and neutral can take different paths, which creates one turn coils generating 50Hz inductive hum.
I grabbed the low pressure sodium lantern from the streetlamp outside my house when they swapped it for a fluorescent lantern. Was a bit surprised to find the cables down the column were sheathed singles.
Could be a council spec dating back to before TW&E was around?
Some councils do like being different just for the sake of it. Several specified D&S gauge sockets for ring mains at one time. Gawd knows why.
And how many council houses have an inductive loop system fitted:-)?
Just before Christmas I was sent to get these working
Powered with T&E and no support at all on the drop from the light fittings. Listening to the T&E fall down the column to the floor was horrible.
It was cold wet and windy and I do not like heights.
Nothing wrong with that.
Not in the real world. They are just as safe as the terminals at a lightswitch or light fitting.
Hidden junction boxes may be a problem.
Are you saying you can have a 32A MCB feeding 4mm^2 cable, then run a
2.5mm^2 spur off it with no additional protection?Andy
Yes, exactly as with a 32A ring circuit. The same limitation applies - one single or one double socket only if the spur is unfused.
(the logic being, as with a ring, the limitation on the number of sockets will limit the maximum load so you can't overload the cable, and the 32A MCB will still provide adequate fault protection for the 2.5mm^2 T&E is the shit hits the fan (or the screw hits the cable!))
It is 2.5mm^2 cable
It wasn't that the earth wire had snapped, it didn't run to the socket at all! There was a junction box beneath the floorboards where the radial split in two and they forgot to take the earth from the junction box.
Only that it means there is less space to poke a rod before you hit one set of joists. The bigger problem is that the rod gets caught in the chicken wire that is supporting the insulation.
Yes I have but I suppose I should have taken photos or called them in before trying to rectify the faults.
Big sheets of chipboard with furniture on, unfortunately. I did consider cutting holes in the chipboard but then I would have the problem of knowing where to cut the hole. At least when you work from the ceiling, you are in the same room, so you can see where the light fitting and switch are.
[about insulation]That makes sense. I didn't realise rock wool was a fire barrier. I think there are some gaps around the edges (i.e. between the joist and insulation), so I am not sure that it is a complete barrier but hopefully I will never need to find out.
[about joists]I only mentioned it because it means there are two sets of joists in the way so you have to weave the wires between them and the rods are more likely to hit one or other set of joists.
[about lives at light]It's not the light switches but the ceiling rose. The light at the top of the stairs has its switched live from the ground circuit but in the loop terminals has the live for the upstairs circuit. The upstairs live is not used by that light but a cable takes the upstairs live and the downstairs ground into the bathroom light and rear bedroom light. So the circuits are sharing a neutral.
(Hope I have not snipped too heavily) Thanks, Stephen.
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