Shower Isolation Switch - Wall mounted

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I have recently installed a new, more powerful shower. This has left me (after a few mistakes in which order to do the rest of the jobs) with a struggle to embed my back-plate (box) and wire the switch.

At the moment I have 10mm^2 cable embedded in a cavity wall.

The feed cable comes up through the wooden frame with enough spare length to be able to loop down so that it comes into the box from above.

The load cable can be manipulated a bit more through wiggling it from the shower side (which is not hanging a shower temporarily).

There is a ragged square hole (just larger than a single gang box) which cannot anchor a plastic dry wall box (I have tried this - and even if I could get the box secure it would still be very difficult to accomodate the two sections of 10mm cable and have enough space and movement to screw down the switch plate).

The hole is about 1 inch away from the wooden frame inside the wall.

How do I get some kind of box secured in my wall?

What size of box gives me enough space to work with 10mm twin and earth? (part numbers would be great too) {NB I have a feeling that single gang 45mm deep is just and just too small}

What type of 45A isolation switch fits onto this?

What is the easiest way to terminate my cables to this switch and fasten it down onto the back-plate?

p.s. I could not find a thread that seems to tackle this area already, if anyone knows a more appropriate place for this topic amongst the 100 pages please refer me.
 
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NB I should also add that I have the right RCD, MCB, earth bonding, etc. and only need to know how to stop myself messing up my wall more and more by experimenting with fixtures too small for 10mm^2 twin and earth.
 
i havent seen any backbox for fastening electrical fixtures to drywall studs in the uk, though they are used extensively in the states. maybe your best bet is to fill in that existing hole, cut another hole over that stud (depending on the thickness of the wall), cut away the stud and recess a metal double back plate in that and screw to the stud. Bring the cables in from the sides, and hopefully if you can recess the back far enough, you should have a bit more space to work in (small gap between back plate and switch). This idea will only work if your studs are, say, 3-4 inches or more deep. Any less then dont attempt it. And watch your screws dont go through the other side! ;)

filling big holes in plasterboard: 1. glue piece of plasterboard to back of hole using string to pull it forwards. 2. fill recess with filler gradually building it up. 3. sand and paint. :idea: diy method, cant go wrong!
 
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i think i would rather screw to the side of the stud than make a big hole in it

do you know if this stud wall is load bearing?
 
my method ensures the back box is rigidly secured - important when using 10mm cable, and ive not seen many metal back boxes with holes in the sides. though i do agree with you about weakening the studs - not always the best idea!
 
crafty1289 said:
ive not seen many metal back boxes with holes in the sides.

p1990210_x.jpg


But if not, there's always this amazing invention:

drill.jpg
 
hmmmmmm . . . . cool.

whats the yellow thing that says dewalt on it? sure ive heard of them, but where . . . ?

;)
 
The simplest and easiest method would be to make the hole largenough (using a pad saw) to accomodate a vertically mounted 54mm deep fluch steel box.

Drill three fixing holes in the side that will sit against the upright. If the upright is wood, then use 1.25" No 8 (4mmx30mm Metric) screws to fix to the upright. If it is steel, then invest in some drywall screws and use these to fix the box as they will self drill into the steel.

Remeber that the entry holes in the box for the cables require rubber grommets to protect the cable.
 
Thanks for all of the ideas.

My wall is not load bearing (otherwise the extension would have already caved in before I bought the house).

I will try a double gang box (probably metal rather than dry-lining plastic) and mount it vertically against the upright (1" to the left of current hole, and 1" down). This will mean screwing the box to the wood first and then feeding the cable in (which makes is sound so easy...)

I may even experiment with 54mm depth, as my wall should accomodate that. Am hoping that my local electrical supplier will have everything in and that I can make a tidier job of the cutting this time. Of course once I do this I will have committed and so my cables will have no spare length to play with if I get it wrong.

Thanks for the reminder about the grommets - will make sure that I get two of these at the same time as the box.
 

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