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Ring Main Joint Box

PG
A kitchen worktop twin S,O, is to be relocated horizontally by about 60cm. 

The ring final cct (RFC) is cabled in buried T&E and the galv' steel back-box is flushed into the plaster/brick wall.

The RFC T&E extension cabling will be buried under plaster, covered in plastic capping along the horizontal  prescribed zone. Visually, it would be reasonable for an electrician to be aware that the route may contain cable(s).

The circuit is RCD protected.

The intent is touse insulated crimp and double insulating tape the jointed cables within the existing box to achieve a maintenance free connection, A 2mm thick (fabricated) plate was to be used to cover the back box and provide additional mechanical protection. The box would then be plastered over.


The questions are:-

1. How many would consider the steel plate back box cover a desirable feature or would a simple plastic cover suffice?

2. Should the original back box be left  unearthed?


Thanks in advance.
  • 0
    As Andy has said the drop to the original socket will not be in a zone, so would not comply with the regs.
  • 0

    PG:




    Typiod:

    if you are moving the socket horizontally from its original position what is there to signify the original drop to the original socket?




    You are correct, all the existing sockets are actually dropping from the ceiling (all concealed by plaster). The circuit extension under discussion would be horizontal - but still within the prescribed zones depicted in the OSG. My point was that it shouldn't be a surprise for someone who was aware of prescribed zones.


     




     

    There will not be any indication where the existing drop to the box that is going to be concealed is.


    Andy Betteridge
  • 0
    What’s wrong with lifting the floor up in the room above the kitchen and moving the cables so they drop straight into the new socket?


     Andy Betteridge
  • 0

    Typiod:

    if you are moving the socket horizontally from its original position what is there to signify the original drop to the original socket?




    You are correct, all the existing sockets are actually dropping from the ceiling (all concealed by plaster). The circuit extension under discussion would be horizontal - but still within the prescribed zones depicted in the OSG. My point was that it shouldn't be a surprise for someone who was aware of prescribed zones.

  • 0
    Thanks - I have never earthed steel capping and was thinking that it may be as well not to introduce earth potential in the box.
  • 0

    Pat Eardley:

    Could you not convince the customer to leave a surface cover plate exposed and accessible ? There are exceptions for crimp joints in BS7671 if you include the phrase 'or appropriate compression tool' but you are still left with the uncomfortable feeling of inaccessibility. If you must do it then I would go for a steel cover plate as it is not easily combustible and gives additional impact resistance. I would earth the back box as if it were plastered steel capping.




     

  • 0
    Zoomup - I'm struggling with the site.

    Thanks for your answer.

    The existing socket will be positioned between the new sink and drainer so should move. I could put a blank on and seal with silicon sealant but it will not look great on the new tiled surface.

    Regards
  • 0

    Zoomup:

    I have a strong dislike for any inaccessible hidden joints. They may fail with time and be a real pain to locate. Is it not possible to leave the existing socket where it is and just run a cable to the additional new socket? That way you know where the joints and cables are located. Or leave a visible plastic blank plate to indicate where the old socket used to be.


    I like the fist sentence of 526.3 regarding joint accessibility for inspection, testing and maintenance. I know that there are exceptions, but they don't count in my book.


    Z.




     

  • 0
    if you are moving the socket horizontally from its original position what is there to signify the original drop to the original socket?
  • 0
    A 2mm thick steel plate hidfden below plaster gives not much mechanical protection.

    Socket or blank plate left in old position is my favourite . If however the old box still complies with zoning requirements in the new situation then you need not bother and your 2mm steel cover is ok. Joints must be permanent ie crimped (not my pref) or soldered etc i.e. permanent.

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