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60 Amp Junction Box.

Zoomup
Mornin' All,

                      I came upon a burnt out terminal on a Crabtree ceiling 50 Amp. shower cord switch yesterday. The cables had become so hot after 3 years of use that the line P.V.C. had completely fallen off the conductor and had left a horrible black smelly sticky mess.


I had to replace the shower cord switch, but the damaged cable was then too short after removing the softened copper and damaged insulation.


So I had to make a trap in the room upstairs, which turned out to be wooden boards over other wooden boards to access the cable below with a view to lengthening one cable. I used a new 60 Amp junction box as it allows two large conductors to overlap and be secured by 4 screws. It is solid and of good quality.


It is this item.....

https://www.toolstation.com/60a-junction-box/p98775?store=N2&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=EAIaIQobChMIufLP1ZD25gIVybTtCh2YWAeiEAQYASABEgJZkvD_BwE


Z.
  • 0
    As for the use of screw terminal as opposed to (MF) junction blocks - are the latter available for greater than 6 mm2 cable; and if so, are the enclosures rated for the current?


    So you may be stuck with traditional junction boxes.
  • 0

    AJJewsbury:




    I asked the NIC about a screw joint box under fitted carpet and was told that could not reasonably be considered accessible.



    If you asked me, I'd say that if you gained access to the location to install the JB in the first place, it can hardly be regarded as inaccessible. Of course, things might change in the future - being tiled over or covered with glued laminate - but that's a slightly different question.


    I tend to concur. It's a pain in the bottom, especially if the boards are T&G, but isn't lifting boards part of the deal?


    IIRC, there was an article in https://professional-electrician.com by somebody from Wago which argued that under the floorboards is not inaccessible.


    If, however, the sub-floor is sheets of board glued into place, followed by wet under floor heating, and then more boards, perhaps with a decorative or durable finish, nobody is ever going to go through that. Under those circumstances, I have made it clear that should any attention be necessary (presumably not with (MF) equipment) the only way in will be through the ceilings.

     

  • 0

    I asked the NIC about a screw joint box under fitted carpet and was told that could not reasonably be considered accessible.




    It also leaves a bump under the carpet, and may be a trip hazard. However it is accessible with a Stanley knife if required.

    Joking aside the bigger problem with anything like that under boards covered by a carpet, lino or whatever is not really accessibility, so much as knowing where it is . in the future, when the notes have been lost.

    If you do not worry about inspection, and I suspect in reality most folk do not open every junction if everything checks out OK, then generally you only need to get to it when there is a problem  and then, like finding a damaged section of cable, if you cannot find the problem,  you may choose to isolate both ends and run a new route around it.

    I have done it the other way up and used a plasterboard mounting box and cover plate in the ceiling below as a inspectable location


  • 0

    Farmboy:




    Zoomup:




    Farmboy:




    Zoomup:...I had to make a trap in the room upstairs, which turned out to be wooden boards over other wooden boards to access the cable below with a view to lengthening one cable. I used a new 60 Amp junction box as it allows two large conductors to overlap and be secured by 4 screws...




    Will it thereafter be accessible - a chance a fitted carpet gets laid?


    F


     




    Hello Farmboy,

                                 no carpet will be laid. The floor is bare wooden boards now. If the removable TRAP was to be carpet covered, I would have written on it in pencil ELECTRICAL TRAP. I didn't do that as it would have spoiled the floor's appearance. The owner is aware of the trap.


    Z.


     




    Hi Zoomup


    Thank you for clarifying your particular example.


    In general, I asked the NIC about a screw joint box under fitted carpet and was told that could not reasonably be considered accessible.


    Cheers


    F


     




    Hello Farmboy,


     the use of the big junction/joint box was essential to extend a short damaged cable to allow for reconnection to a new shower ceiling switch. I consider that the new connection is permanent and needs no inspection or future regular access. Junction boxes have been hidden under floors for years with no problems. I do not use junction boxes in new installations or in rewires if possible. There should be no need, but in repairs they can be very useful. I always used to screw down traps in floorboards and mark the trap ELECTRICAL TRAP. This allowed for future access if necessary. But was rarely if ever needed. The full details need to be known before any professional body comments upon hidden junction boxes.


    Z.

  • 0
    I can imagine that you envisaged this type of event Andy.

    https://hackaday.com/2020/01/08/fail-of-the-week-thermostat-almost-causes-a-house-fire/


    Z.
  • 0

    I asked the NIC about a screw joint box under fitted carpet and was told that could not reasonably be considered accessible.



    If you asked me, I'd say that if you gained access to the location to install the JB in the first place, it can hardly be regarded as inaccessible. Of course, things might change in the future - being tiled over or covered with glued laminate - but that's a slightly different question.

      - Andy.
  • 0

    There is a world of difference in a 40 Amp. shower load and a lighting load of a few L.E.D. lamps Andy, as well you know. The possible heating effects are totally different. You are cross threaded. There is no way that the lighting cables could contact the metal light switch plate insulted or uninsulated due to physical separation.



    Ah, you've been telling us half a story then. You never mentioned the the lighting circuit for that metal switch was dedicated to just a few LED fittings - there are still enough GLS lamps and 50W halogen downlighters about that we can't safely assume that a lighting circuit can't be significantly loaded. I'd dispute that the heating effect will be totally different - while the load currents will certainly be smaller, the conductor size will also be substantially smaller - so requiring much less heat to reach a damaging temperature. Sure you'd need a higher resistance to produce the same I²R - but what limits the resistance of a bad contact or loose connection? You also haven't mentioned the physical separation before (despite me describing the possibility in the other thread) - if you do have a way of ensuring that, that would be reassuring.


      - Andy.
  • 0

    Farmboy:




    AJJewsbury:


    Fitted carpets are easily removed...


    ?... a matter of judgement I guess as to what accessible / inaccessible is - a homeowner who doesn't want their fitted carpet pulled up may disagree with you, and it's existence may get lost in the mist of time, particularly if the owner moves, but perhaps a notice at the CU may suffice.


    F


     




    You offer them the alternative, plastic minitrunking run up, across and back down the wall.


    Andy B. 

  • 0

    Zoomup:




    Farmboy:




    Zoomup:...I had to make a trap in the room upstairs, which turned out to be wooden boards over other wooden boards to access the cable below with a view to lengthening one cable. I used a new 60 Amp junction box as it allows two large conductors to overlap and be secured by 4 screws...




    Will it thereafter be accessible - a chance a fitted carpet gets laid?


    F


     




    Hello Farmboy,

                                 no carpet will be laid. The floor is bare wooden boards now. If the removable TRAP was to be carpet covered, I would have written on it in pencil ELECTRICAL TRAP. I didn't do that as it would have spoiled the floor's appearance. The owner is aware of the trap.


    Z.


     




    Hi Zoomup


    Thank you for clarifying your particular example.


    In general, I asked the NIC about a screw joint box under fitted carpet and was told that could not reasonably be considered accessible.


    Cheers


    F

  • 0

    AJJewsbury:




    The cables had become so hot after 3 years of use that the line P.V.C. had completely fallen off the conductor and had left a horrible black smelly sticky mess.



    Fortunate then that the protective enclosure wasn't completed by an unearthed metal plate then.

     

     




    There is a world of difference in a 40 Amp. shower load and a lighting load of a few L.E.D. lamps Andy, as well you know. The possible heating effects are totally different. You are cross threaded. There is no way that the lighting cables could contact the metal light switch plate insulted or uninsulated due to physical separation.


    Z.

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