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What is the best way to wire ceiling lights?

Arran Cameron
The ceiling rose junction box with its loop-in wiring is now really showing its age and is no longer a practical (or even safe) installation for most residents who wish to install fancy light fittings. It is still, however, the most common arrangement for new build houses and rewires, probably as the result of the electrician's training and how they consider it to be the norm or they cannot think of (potentially better) alternatives.


So, what is the best way to wire ceiling lights? Should neutral wires be taken to the switches or not?
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    Dbat:



    What does it matter what it was made for? Have you ever tried to do some basic circuit fault finding? Easy access and splitting up of cables is the name of the game, and your going to struggle if the previous person went down the central hidden junction box route aren't you?


    Has anybody here actually carried out fault finding on a lighting installation using Surewire junction boxes?


    Is a loop-in topology preferred over a radial topology by electricians for ease of fault finding?
     

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    With real fault finding you have no idea what the wiring style is until afterwards, only that something is not right,  and actually in anything that is not a brand new house, you have to assume it may well be a hybrid of a bit of this and a bit of that and using every system known to man used in different areas.  If for example a light is not working, it is not even obvious what circuit it is on. (I have found a house where the upstairs lights, all of them, plugged into a socket hidden behind a wardrobe, the neatly labelled 'upstairs lights' fuse did nothing - I presume it was a temporary fix in the middle of some building work, and the chap or chappess never came back to finish the cable run, after all 1mm T and E is not a great fit in a 13A plug.)

    Visit a friends house and try and guess the wiring routes and methods by what you can see. That is all we can do.

    There may well be surewire or other JBs or even choc bloc or tape and twist joints buried in unreachable parts of the installation that did not seem to be part of the problem. Even when you leave it is quite likely you will still not know for sure if there are joins in the parts you did not dismantle, though you may suspect, if there are clues such as the wires at the switches are 1mm and white jacketed and the wires at the fitting are 1.5mm and grey.

    Often though it is not that obvious, and sometimes it is better if a whole branch of unexplained mystery is cut-off and abandoned as beyond economic investigation and possibly non-compliant, and a new wire routed to get a supply to the load by another route and an obvious wiring method. Novel methods just confuse inspectors and repairers, and in some cases the original installers as well.
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    One criticism I have of them is that they do not manufacture a junction box that fits inside an electrical back box.



    No need - choc blocks (or wagos) in a back box with a blank plate over serve perfectly well.


      - Andy.
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    Dbat:

    Have you ever tried to do some basic circuit fault finding? Easy access and splitting up of cables is the name of the game, and your going to struggle if the previous person went down the central hidden junction box route aren't you?




    I was thinking of this thread today as I was poking some cables into a Wago/Connexbox MF JB. Splitting a circuit is all very well, but ordinary Wagos (i.e. not the lever type) are not really meant to come apart. Yes, I know, you can twist and pull, grunt a few times, and they will separate. ? As I was looking at some adjacent plumbing, it occurred to me that these things are not meant to be pulled apart. They are MF for a reason - they are for life!


    As far as finding JBs is concerned, even without a map, surely logic dictates that they will be above (or below) a branch to a particular socket.


    As far as rodent damage is concerned, how do you find it short of pulling up floorboards one at a time? Yes, non-permanent connexions may allow a fault to be narrowed down to a particular length of cable, but that does not tell you where the damage lies. Or would you simply disconnect the faulty segment and bung in a new one in parallel as it were?

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    Faulting by halves is the standard approach to fault finding an electrical circuit.


    Guess where the middle is, separate the two halves of the circuit, identify the fault half and repeat the process on that half, then keep repeating until you get to the fault.


    It is not unknown to half to chop a cable into sections with cutters to break it down for testing, then to have to join it back together again removing the fault as you do so.


    If you can simply disconnect the cable ends at switches or light fittings this can be done quite quickly and efficiently.


    If you have to start lifting carpets, laminate flooring, tiles, the sub-floor and floor deck itself to find the junction boxes then separate the cables, you really are not going to be popular with customers if you installed the junction boxes or for that matter even if you are the person trying to sort the problems out.


    Andy Betteridge 


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    Sparkingchip:

    Faulting by halves is the standard approach to fault finding an electrical circuit.


    Guess where the middle is, separate the two halves of the circuit, identify the fault half and repeat the process on that half, then keep repeating until you get to the fault.


    It is not unknown to half to chop a cable into sections with cutters to break it down for testing, then to have to join it back together again removing the fault as you do so.


    If you can simply disconnect the cable ends at switches or light fittings this can be done quite quickly and efficiently.


    If you have to start lifting carpets, laminate flooring, tiles, the sub-floor and floor deck itself to find the junction boxes then separate the cables, you really are not going to be popular with customers if you installed the junction boxes or for that matter even if you are the person trying to sort the problems out.


    Andy Betteridge




    What are the commonest faults found on lighting circuits?


    Is a loop-in topology with ceiling rose junction boxes more or less reliable than a radial topology with ceiling rose junction boxes? Which of the two topologies is easier to fault find?


    Are installations where just one cable emerges from the ceiling for each ceiling rose or light fitting generally more reliable than installations where 3 cables emerge from a hole in the ceiling for each ceiling rose or light fitting?


  • Former Community Member
    0 Former Community Member

    Arran Cameron:




    What are the commonest faults found on lighting circuits?

    Specifically for lighting they tend to be at luminaire positions (often heat related or poor terminations due to space constraints), followed by switch positions (removal/twisting about for decoration etc) and then more common to the rest of the installation to the wiring generally where buried in walls, under floors etc (over ambitious SDS or nail gun activity)


    Is a loop-in topology with ceiling rose junction boxes more or less reliable than a radial topology with ceiling rose junction boxes? Which of the two topologies is easier to fault find?

    If you know where the JB is, and have easy access - for me the latter. I often used a double socket box strategically positioned as a joint box for a group of luminaires and switches (what was often known as RB4 method after the catalogue number of the JB)


    Are installations where just one cable emerges from the ceiling for each ceiling rose or light fitting generally more reliable than installations where 3 cables emerge from a hole in the ceiling for each ceiling rose or light fitting?

    In my opinion yes (but that very much depends on the luminaire that's being installed) - a ceiling rose with loop in is pretty bomb proof - cramming all the connections into an IKEA chandelier less so)




     




     

    Regards


    OMS
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    True in town perhaps, but if the location is rural or agricultural, then I'd add that common faults can include mice, squirrels (do not laugh, they really do make a right mess) and in less used outbuildings rain water ingress. The animals tend to attack cables  in mid span, water damage only serious at hidden joints.

    Heat damage from 100W lamps in 60w holders is getting a lot rarer, as the 100W lamps are going.
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    Will this thread run for ever?


    A scan of recent posts suggests two points of concern - junction boxes and accessibility.

    Junction boxes


    I would describe these as non-preferred; they provide extra terminal junctions in places that have no actual function. I am sure I could wire a house from scratch using no  junction boxes. I am sure most diligent electricians would prefer to do the same.


    In an ideal world one would wire a house with foresight of everyone's requirements for at least the next 50 years. We do not of course live in such an ideal world.


    My present house, a bungalow, when I moved in, had a single ring circuit serving the front and rear extensions. The central area was served by sockets connected in an unattractive "tree" layout. I wanted to make things "conform" so I rearranged this into two ring circuits, with some of the central area sockets as spurs. Yes, this required a few junction boxes.


    The house lighting was all on just one sub-circuit serving 20-plus lights. I rearranged this into three sub-circuits. Then I needed to provide a two-gang switch at the lounge door for both ceiling and wall lights. Then I wanted to add a passive infrared detector in parallel to the outside light switch, preferably without chasing to run extra conductors to the switch. Overall this also required a few junction boxes.

    Accessibility


    Many years ago, when accessibility was less-well defined in the Regulations, I had an argument with an electrician who wanted to install a junction box where it would be plastered over. His point was that he and I knew where it was and it would be possible to cut a hole in the plaster to access it.  I would define accessibility as follows.
    • Accessible to touch: Positioned where anyone can touch in  normal living circumstances. Clearly not a place for live terminals.

    • Accessible for inspection: Positioned where they can be touched only after removing some type of cover.  This could include junction boxes in loft areas.

    • Inaccessible: Can be reached only by causing damage to the fabric of the building.



    On the (fairly rare) occasions where I have needed to leave a junction box or other type of terminal connection under a floor, I have left a short, "loose" board above it, usually screwed down rather than nailed. This passes as accessible for inspection. Of course, as others have said, fitted carpets or tiled floors do not make this type of access easy, so I try to avoid under-floor junctions as far as possible. This is easy in a bungalow, less easy in a multi-storey house.
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    A bog standard ceiling rose is just a junction box when wired loop in.

    Behind a plateswitch or indeed a socket is effectively a junction box quite often.

    These are places that are relatively easy to inspect/disconnect/test.

    Deliberately adding junction boxes under floors, in lofts, in walls is not a very clever thing to do usually.


    Reminds me of fan isolators I sometimes see (or rather do not see) .

    Bathroom fan, timed overun etc, isolator in loft, nobody knows it`s there! I always put them just outside the bathroom but high up enough to be not normally accessable )i.e. not switch height) but readily viewable and capable of operation by using steps or a long stick etc

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