Bunched cables though stud timbers

[ban-all-sheds]

As for earthing it, I'm sure one could find a way, but some might argue that (surprisingly) 522.6.101(iv) doesn't explicitly say that 'mechanical protection' (as opposed to sheathing, conduit, trunking or ducting) necessarily has to be earthed

So it doesn't.

Now there's a thing.

And now I come to think of it: "...sufficient to prevent penetration..."

Not "resist". Not "prevent reasonably foreseeable".

Just an unqualified, absolute, "prevent".

I wonder how you could protect a cable in a way which prevented any nail, any screw, any 'and the like' from penetrating the cable no matter how it was driven into the wall.

For 522.6.101(iv) to be complied with there would not be able to be any way known to man to drive a nail or screw or the like through the protection into the cable, no matter what materials, force or technology was used.

I don't think they thought that one through very well.

 

[DaftPunk]

I reckon this pretty much voids that regulation.

 

[JohnW2]

As for earthing it, I'm sure one could find a way, but some might argue that (surprisingly) 522.6.101(iv) doesn't explicitly say that 'mechanical protection' (as opposed to sheathing, conduit, trunking or ducting) necessarily has to be earthed

So it doesn't. ... Now there's a thing. ... And now I come to think of it:
For 522.6.101(iv) to be complied with there would not be able to be any way known to man to drive a nail or screw or the like through the protection into the cable, no matter what materials, force or technology was used. ... I don't think they thought that one through very well.

Agreed. There should have been some qualifiers in their wording. I would also imagine that if the protection is conductive (i.e. metal), and could conceivably come into contact with live cores of the cable, then they probably 'intended' to require it to be earthed.

[and, interestingly, I see that the bold italic text in the above quote shows up fine on my screen, although regular italic text still doesn't!]

Kind Regards, John

 

[frank999]

I agree, my structural plans spec'd that we 'nail' restraint straps for each joist into the flange of our 203x203 steels beams (see below), that Hilti 'Gun' can force a 'nail' right through the 10mm steel flange, an explosive charge forces the nail and almost 'welds it' to the steel, it will go right through in places ... so should I ditch the thin Galv capping I bought from Screwfix then ??

Your right, the cable coming up from the floor are outside the zone, either way its all going in Galv 50x50 Trunking, just makes sense to protect it, i'll cut and screw a patch of the trunking over the footer plate of the stud as the hole its coming up from is less than 50mm from the centre.

I have cables running up chased channels in walls by the stairs - less than 50mm from the surface - galv capping would be ideal - but in light of the above - how do I deal with that, put it all in steel conduit - and use the 'bunching' factors to work out how many cables to a piece of conduit, the chase runs up the hall wall - I really cant see a wardrobe corner making an 'instrusion' - is there no way a more sensible approach can be taken with this 'protection ?

View media item 48354

 

[RF Lighting]

Yes, run your cables in the prescribed safe zones like everyone else, and ditch the non compliant mess of scraps of trunking, conduit and capping.

 

[frank999]

The floor is all glued and fixed down - it isn't gong to come up easily, if its 'protected' correctly its to regs ? I will have shown due diligence by at least using strong Galv Trunking - the cables run down under the floor 50mm from the surface.

Its now how I intended the cable run to look like - we moved the stud position (and door) after the cable were routed - I'm sure this occurs on occasion on sites.

 

[RF Lighting]

Diligence is not good enough. Your work MUST be compliant.

I can not see how you will completely surround your cables in earthed metal right the way through the stud work which is what's required.

 

[frank999]

Thanks, diligence point noted - not sure what you mean, I will surround it with with 50mm Square Trunking ... where it passes through noggins or plates less than 50mm I will cut out a plate from a piece of trunking and fix that on the stud sandwiched between that and the plasterboard ... I will make the plate wide enough so that screws if screwed at an angle cannot penetrate.

But again coming back to the Hilti Gun example - how far do you have to go to protect.

 

[RF Lighting]

That is not acceptable.

The wiring must be fully surrounded by earthed metallic containment at any point where it is installed outside a safe zone.

 

[JohnW2]

But again coming back to the Hilti Gun example - how far do you have to go to protect.

Good question. Standard galvanised steel conduit is certainly normally regarded as adequate for cable protection and, IIRC, that has a (steel) wall thickness of around 2 mm.

Kind Regards, John
Edit: typo corrected ("3" --> "2")

 

[ban-all-sheds]

The more I read of this, the more I realised that there's a significant amount of building work going on, and a significant amount of associated electrical work which is being done by an insignificantly competent person, and that the whole project is receiving an insignificant amount of proper planning and project management.

The OP seems to think that if he keeps ignoring the question of "who put those cables there" then he will also be able to ignore the fact that the electrical work is non-compliant.

When he applied for Building Regulations approval, IHNI what he said, or allowed to be said on his behalf, or what LABC assumptions he by default tacitly accepted, about who would be doing the electrical work, but I don't have any great expectation that he would tell us if he was asked.

I'm pretty sure, though, that they did not agree to it being done by whichever clown is actually doing it, nor did they agree to it being done to this standard.

Unless the OP wakes up, smells the coffee, and accepts that glued and fixed down floors or not, if he does not get the electrics done properly, and done in the way that is in his approval[/b], he is heading for an almighty crash and burn when it comes to completion certificate time.

 

[ban-all-sheds]

Standard galvanised steel conduit is certainly normally regarded as adequate for cable protection and, IIRC, that has a (steel) wall thickness of around 3 mm.

But it's earthed, which, as you drew to our attention, plain mechanical protection as per 522.6.101(iv) is not.

And galvanised trunking is not 3mm thick, nor does it have any compliant means of earthing when it's concealed.

 

[frank999]

3mm ?? - I used to work in an electrical wholesalers - we never sold any conduit with a 3mm wall ...

Ok, thanks, good to know your opinion, ok so in view that the floor is down, and not coming up - it might be better to run the cables in several pieces of metal conduit rather than one 50x50 trunking - I can run it straight up from under the floor (50mm below) through the noggin, the trunking would take too big a hole out of the wood.

I can use a 80x160x50mm metal enclosure with a blanking plate for the Wagobox cable join, tap and fix the conduit in and out of that on the way up.

I assume the regs will require me to fix the conduit using saddles or similar.

So a 3mm wall is seen as the acceptable standard - blimey !

 

[ban-all-sheds]

I assume the regs will require me to fix the conduit using saddles or similar.

Why don't you read them?

Surely you aren't being so foolish as to be doing electrical design and installation work without having a copy of the regulations?

So a 3mm wall is seen as the acceptable standard

Seen by whom as acceptable for what?

 

[JohnW2]

But it's earthed, which, as you drew to our attention, plain mechanical protection as per 522.6.101(iv) is not.

True - but, as we have agreed, the wording of that reg is so flawed as to be almost meaningless.

And galvanised trunking is not 3mm thick ....

Apologies - that was a slip of the typing finger (now corrected) - I intended to type "around 2mm", which I think is about right (1.6mm seems quite common, but IIRC, so is 2mm).

... nor does it have any compliant means of earthing when it's concealed.

An interesting thought. Are you therefore suggesting that there is no way of complying with 522.6.101(ii)?

Kind Regards, John