Making/modifying back boxes

Discussion in 'Electricians' Talk' started by robertpstubbs, Mar 20, 2019.

  1. robertpstubbs

    robertpstubbs Active Member

    Are there any rules about the materials and construction of back boxes? And could you modify them or make your own?

    Eg could I cut the back off a metal back box and weld on an extension made from another to create more space?
  2. rogerk101

    rogerk101 Well-Known Member

    Wouldn't it be easier just to buy deeper boxes?
  3. robertpstubbs

    robertpstubbs Active Member

    As far as I know the deepest are 47mm, but I was looking for more room.
  4. rogerk101

    rogerk101 Well-Known Member

    I've used the 47mm ones for shaver sockets but never needed deeper.
    What are you trying to fit in there such that you need them deeper?
    To answer your original question you can make back boxes out if wood. I've replaced many a wooden one with metal ones over the years but can't see why you can't do the other way round
  5. Bob Rathbone

    Bob Rathbone Well-Known Member

    As I understand it, the box must form a fire resistant enclosure and be complete, no sharp edges to damage cables and have approved lugs for the accessory. What you propose as a 'special one off' would be ok as you will be joining two approved enclosures.
  6. robertpstubbs

    robertpstubbs Active Member

    This would be for 24-module grid switches. It might even be cheaper to make boxes from scratch top rather than buy the MK ones.
  7. robertpstubbs

    robertpstubbs Active Member

    Are you sure wood would be OK?

    Actually the box for my CU is very well made from hardwood and original from the construction of the house. It was years before I noticed it wasn’t plastic.
  8. rogerk101

    rogerk101 Well-Known Member

    If it's built into a fire resistant wall, say, a brick wall, it is OK for it to be made out of wood.
    This means it should be OK if it's built into a stud wall with plasterboard on both sides.
    However, if it's sitting proud of a wall then it should be made out of fire resistant material ... but then it wouldn't be called a back-box, would it? :)
    If it's to house all the wiring for a 24 module switch grid, then if you're any good at welding or metal work, then you could probably make one cheaper than MK's ones and you'd get the depth you want. But then what's your time worth?
  9. Wayners

    Wayners Well-Known Member

    Yes.. It's fine just sink deeper the use another box at 25mm or other to line to the surface.
  10. robertpstubbs

    robertpstubbs Active Member

    Alternatively could I sink a metal cabinet in the wall and mount the switches in its door?

    If so could I still use 7-strand 1.5mm2 singles or would I need to use flex?

    (Lifts often have hinged switch panels but they are typically 12/24v not 240v.)
  11. Bogle Crag

    Bogle Crag Active Member

  12. robertpstubbs

    robertpstubbs Active Member

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