Tails in cavity wall

[catdog1121]

So I have a consumer unit to change, the consumer unit was in the garage but it has been converted to living accommodation years ago. The utility cupboard is on the outside wall, the consumer unit is obviously on the inside wall but near the ceiling.

The issue is when they changed the garage to living accommodation they created a second skin using breeze blocks. The tails from the utility cupboard were run in the cavity wall between the meter cupboard and the consumer unit, these tails need upgrading to 25mm plus 16mm earth.

I know just running new tails in the cavity will not provide enough protection, the cables would be less than 3m so from a DNO point of view thats fine. Its going to be hard enough to run the 25mm cables through and up the cavity wall let alone put any sort of copex to protect it, the alternative is 25mm 3 core SWA however then would need a fused isolator box in the meter box to terminate. (Can't find any sort of wiska box that would be able to make connection from tails to 25mm 3 core SWA).

Im sure I am not the first to come up against this issue so thought I would see what others thoughts were.

 

[loz2754]

Hi - agree it’s possible to drill through. I’m thinking that 522.6.204 (iv) doesn’t require the protection be drill proof, just prevent penetration by nails and screws. I’m relying on the British manufacturer who recommends it for this job. Maybe I’m too trusting?

In the end it would be better if the tails were not there in the first place.

View attachment 49504

Electrical safety first recommends minimum 3mm steel for this application

 

[Bobster]

If the cut out is 100A then 25mm tails are mandatory irrespective of load (taking into account diversity).

Care to share the regulation that states this?

 

[DPG]

No cables are allowed in a cavity other than meter tails 'which must pass directly through i.e. perpendicular to the wall'
So the choices are you either run up the outside then go straight through the wall,

Not sure what you mean here - any cable can pass directly through a wall.

 

[dksanders]

Care to share the regulation that states this?

OSG 2.2.3.1 Consumer's Tails, 2nd paragraph. '...and the minimum cable size should be 25mm"

 

[dksanders]

Not sure what you mean here - any cable can pass directly through a wall.

Yes, but not run in a cavity. You're right, any cable can pass perpendicularly through the cavity, it's preferred that meter tails do so also, however they are the only cables that may deviate e.g. enter the cavity then go up slightly, then exit, recognising that we don't live in an ideal world.

 

[Ian1981]

OSG 2.2.3.1 Consumer's Tails, 2nd paragraph. '...and the minimum cable size should be 25mm"

That is not a regulation, mearly guidance going to a default csa for fuses that are rated at 100 amps.
There’s no such regulation preventing you using say 16 mm tails as the fuse could be rated lower than 100 amps

 

[Bobster]

OSG 2.2.3.1 Consumer's Tails, 2nd paragraph. '...and the minimum cable size should be 25mm"

The OSG is a guide, nothing more. It is not regulation.