Current rules regarding fireproof cable mounting

[Chris Green]

Following on from discussion in a recent thread here can anyone fully clarify the latest rules about fireproof mounting of cables.

My understanding of the new rules was that just about all cables in a domestic installation must now be fixed in a way that won't fail in a fire (at least not until silly temperatures are reached).

Thus the only cables which don't need fireproof fixings are:-

Cables resting on plasterboard (or above rafters over plasterboard) in a ceiling void.

Cables running across a floor

Cables embedded in a wall

Have I got this (basically) right? It means that all cables clipped to walls as well as cables across thresholds and clipped to ceilings from below must have fire resistant fixings. This includes cables in conduit as well as clipped direct.

Are cables within a stud wall OK without fire resistant fixings, i.e. are they a version of "cables embedded in a wall"

[Andy Burns]

BS7671 18th says

"521.10.202 Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire."

The internet seems full of sparkies spouting their personal (over?) interpretation of that section, I don't have access to the current regs to see what else they have to say ...

[Robin]

Not much. It's a typically brief requirement* that leaves a lot to case law...oh, sorry, mere punters have no practicable way to contest the sages.

*it's quoted almost verbatim in e.g.

[Tim Lamb]

Remarkably clean and well kept hands (pictured) for a working electrician!

[Andy Burns]

Metal clips, held by plastic rawl plugs? That seems to be one of the bees various commentators have in their bonnets ...

[Robin]

Your eyes are better than mine as I'd thought it could be into one of their cavity wall fittings

[John Rumm]

Even those tend to be Ali, so arguably less than ideal.

[Chris Green]

OP here, yes, exactly. It's all so ill-defined at the moment that one wonders whether to bother at all until we know what's *actually* required.

[Robin]

I generally reckon on doing what Adam or John say - and not just 'cos they a lot bigger and younger than me :)

[charles]

As I understood the requirement, from a seminar a few years ago, it was to prevent a reoccurance of the time a firefighter got trapped im dangling mains cables - and was killed. So, really over doorways is the crucial pont.

[Harry Bloomfield, Esq.]

Chris Green expressed precisely :

The only places where any special care needs to be taken, is where surface mounted cables, as a result of a fire, can drape down across an escape route - any escape route, any dorr way.

[Andy Burns]

I think that was what led to 17th ed

"521.11.201 Wiring systems in escape routes shall be supported such that they will not be liable to premature collapse in the event of fire."

but then 18th ed widened it to all cables

"521.10.202 Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire."

[Chris Green]

Yes, that's why the requirement was added but the wording in the regs means that one has to do a lot more than just 'over doorways' to conform.

If the requirement actually said 'over doorways' it would make things a whole lot easier!

[Andy Burns]

17th ed. did say "in escape routes " but now 18th ed. effectively says "everywhere"

[Robin]

Prompted by that I asked them if the fixings were fire rated. In reply they simply sent me a data sheet which doesn't specify the material but does state they "offer excellent fire performance". I guess that's probably fair compared with a plastic plug; and that a chunk of aluminium or zinc alloy or whatever inside plasterboard or concrete will last a lot longer than a thin cable clip fully exposed. But it'd be nice if the BS 7671 gurus had given some thought to the point.

[Fredxx]

Recently I've used these. Easy to fit and stronger retention than I might otherwise expect in plasterboard.

I note masonry screws are recommended instead of plastic or aluminium rawplugs in solid walls.

[Andrew]

even if hidden inside voids protected by 30-min plasterboard ?, or "everywhere where cables are surface mounted on ceilings and/or across doorways" ?.

[ARW]

Hi Chris

Any of these links any good?

Cheers

[Fredxx]

It would help if I added the link: