I'm planning on fitting a new 17th edition metal CU and will fit glands to the mains tails but not sure if glands are necessary for the surface T&E coming in the CU from the top or would grommets be okay?
Obviously I need to make sure the grommets are a close fit on the cables but other than that I can't see why glands would be necessary. Is it to stop the cables being pulled out?
BTW I'm a retired time served sparky but never part P due to working in an industry that was exempt from this.
The top is supposed to meet IP4x (1mm probe cannot penetrate IIRC).
The classic solutions are to either fill up the gaps with silicon of cable compound (TLC sell this) or conduit or run a bit of trunking over the top.
I used short (8") stubs of conduit to take the cables above the ceiling, but they are otherwise open at the top.
Mine is in the cellar - at the top of the stairs. On what was a plain brick wall. So I simply dry lined the wall in that area, so all the cables to the CU are concealed behind that.
Note that both tails *must* enter through the same hole in a steel case. (Ideally, so should the earth connection.) Otherwise you have created a current transformer core around each cable which will create eddie currents in the steel and heat it up when you draw high current. When they go through the same hole, the magnetic field cancels out and avoids this problem.
Not if they are fixed wiring which is fixed down. If for some reason you have a flex coing out of the case, then that would need a cable grip in the form of a gland.
Some metal 17th edition metal CU's (certainly Wylex) have an optional grommet kit you can buy for sealing the cable entries.
I've heard that over the years, and it's what I would do, I'm sure that one bloke's video doesn't prove that it's entirely wrong, but ...
I've seen this effect with long runs of steel conduit. I'm surprised it would be noticeable with such a thin layer of steel?
Not sure why I phrased it like that, it doesn't prove it's wrong, in fact it proves it does happen. What I meant was that it seems such a minor effect, does it actually justify outlawing it?
is my choice of gland for the job.
Bit more like it, rather than £15 for the Wylex one at screwfix.
Wylex ramped up their prices a few years ago.
There is still this at screwfix
Wish I'd read that about the tails having to use the same hole before I fitted it! I now have a snagging list item! I might even cut between the two holes as the tails are so rigid and such a pain to unthread.
It's all working except for a suspected 'borrowed neutral' which trips both ELCB's on the stairs lighting (which I will sort).
Thanks all for the useful info.
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