I got a 2 gang surface mount back box the other day that had cable grips in it, which I thought was a good idea.
But it only had two, and they weren't opposite but one on the side and the other top (or bottom). Has anyone any idea why this would be? Why not fit them on all four sides?
For a cooker switch with an outlet cable, probably. Cable grips take up space, and cost the manufacturer money, so they don't fit four. Only one will be likely to be required.
Owain
You could get a back box with conduit knock-outs, and fit cable glands.
Really? If there's a chance the cable could be put under strain, shouldn't it be protected from that by conduit, etc?
No. They are standard pattresses for cooker units. Two grips at different positions, but only one to be used, depending upon required orientation. The cable to be secured will be the flexible one to the cooker and needs to be capable of movement to allow cleaning behind.
SteveW
Oddly, I ventured into my 'loft stock' (bits bought and not used) the other day for a back box (single) and found a new one which also had a cable grip. I don't recall buying it, nor was the bag market as having a grip etc and I don't recall seeing one before. Grips on the rear of a face plate for fused/switched flex outlets yes but not on the back box.
Ah, makes sense. Cheers.
Ah - got you. So not a 'normal' back box? But just as easy to add a cable clamp to an ordinary one, as to source a special for just that job.
They are also extra deep at 47mm to allow for terminating the thick and unwieldy cable needed for a combined oven and hob. So yes they are not a "normal" pattress, but they are a standard one for that specific job. The cable clamp (often only a single one supplied) is usually a single piece (plus screws) and relies on the other half of the clamp being a mounded in section of the box.
For example:
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