Hi all,
Am going to replace and move CU. will be using longer meter tails (with a suitable switchfuse)
Now is it acceptable to route meter tails between the ground floor ceiling and the first floor floorboards?
There are already holes in joists halfway between top and bottom. joist depth is 185mm so I can run the meter tails through the existing holes.
the route is up the wall, through the ceiling - floor void then through a wall and the down to the new CU location.
I do not *think* that contravenes any specific regulation.
What you need to do is consider damage potential. If the holes in the joists are half way between top and bottom and so (presumably) > 50mm from either floor or ceiling surface, then it is highly unlikely anyone could bang a nail through the cables from either direction.
Which all sounds OK if I undertsnad you correctly.
If the cables are surface mounted on the walls at both entry and exit, there is no problem there either.
As Andrew says >50mm from the surface is fine.
Your new CU now seems to be going into a different position to the one it was going to be in. Is a certain female changing her mind about where you are allowed to put your new CU? If so then decide where you want it and say to her whilst pointing at the said spot "the CU cannot go there". Job done.
Pedantic question: would those carrying out building control checks and EICRs ignore as de minimis any bits where the bends in the meter tails mean they are out of sight but less than 50mm from the surface of the ceiling? I have in mind that 25mm tails have a minimum bend radius of roughly 70mm. So - unless a few inches of the ceiling are cut out either side to expose the S-bend - there must be a bit just after they go into the ceiling and just after where they come out which technically doesn't comply. And IIRC the provision in the regs for a 150mm "safe zone" only applies to cables in walls, not cables in ceilings.
Of course I hope for the OP's sake the answer is that even a bolshie inspector would not quibble.
As installed when a new meter was fitted, bend diameter 60mm.
The "50mm wall rule" is regulation 522.6.6 which does not apply to ceilings
- 50mm above ceiling and below floor (above) *when passing through a joist or support* only.
Cables may lie on the ceiling in other locations and often do.
If the joist is a problem, clause (v) of the same regulation says you may mechanically protect it against nails and screws - (eg with steel plate).
As you are not likely to use an SDS on a ceiling, 3mm or so plate should be enough.
The regs say "within 150mm of the top of a wall":-) And they are about as comprehensive as a Star Trek captains directional coordinates.
Out of Sight, Out of Mind
I only have access here to the draft regs and in those 522.6.6 reads "A cable concealed in a wall or partition at a depth of less than 50 mm from the surfaces of the wall or partition shall: ... (iii) be installed in a zone within 150 mm from the top of the wall or partition or within
150 mm of an angle formed by two adjoining walls or partitions." I took the opening words to mean 522.6.6 does not aply at all to cables in a ceiling (or floor). I thought that's also why 522.6.6 and 7 were separeate and distinct from 522.6.5 which does deal with ceilings and floors. But looking at that again in the light of Tim Watts' comments I can see it might be a way out.
That is the 50mm rule I had in mind.
Yes indeed, but I had thought that under the 17th edition such cables routinely needed RCD protection. Looking at (the draft) text in the light of your comments I see though that it does indeed only require a
50mm gap from the top and bottom of a joist or batten it passes through. Seems a bit bizarre to me given how tight they have made the regs for walls but I guess they have risk-assessed it on th basis that far fewer people fix thinsg to ceilings/floors than to walls. So thanks for educating me - and for providing at least a small example of where some small risk was accepted.
not really, its just I'm optimising the meter tails route from meter cupboard to new CU location before buying materials and actually doing the job.
Basically route one was through wall from meter cupboard into d/stairs family room
travel up almost to ceiling, turn left travel for 2 metres then hole through wall above door way into hall way and then into CU in hall way.
Main issue with this route 1 is that the meter tails have to then cross the room light switch cable which is by door.
2nd route is similar but actually go up into ceiling-floor void, through the joists, then drop back down to above door and then through to CU. Main advantage is less 3mm plate steel needed.Hence my question.
Do you happen to know what cable that is pl? In the light of what you have I've checked the manfr's specs for the tails here: they state a minimum bend radius of 4 x the diameter (as in the OSG) and a diameter of 11.2 giving a minimum radius of 45mm. That's a good deal less than the 70mm I thought but still adds up to a diameter of nearly 90mm. Something more flexible would be worth knowing about "just in case".
The OD (sheath) is 10mm, but I've no tables to turn that into cable size. And I've no idea of the size of the "Company fuse", the meter has a max rating of 100A.
Thanks for looking/measuring.
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