Running cables inside a cavity wall

[phil d]

In the wholesalers today and this guy comes in from a well known solar firm looking to buy a set of cable rods, he hadn't got any because he'd ripped the ends off his trying to drag a cable in, "we're trying to get a 6mm t&e from the mains downstairs to the inverter in the loft" he informed me, "we're not supposed to do it this way, but the guy won't let us run a conduit up the wall outside".

You have to wonder,if the guy knows it shouldn't be done like that, why is he doing it, and more importantly what else are they doing that they shouldn't?

 

[Lurch]

Meh, could be worse. I think I spent most of the latter half of the 90's putting 6mm T&E up cavity walls.

I think though with cavity wall insulation being more prevalent these days I'd make it 10mm² just to be sure, most inverters are on a 16A anyway though, 6mm² is just for the tighter volt drop, should be lower running it vertically anyway.

 

[steptoe]

But its a simple fact that you are not allowed to run any cable up a cavity wall.

 

[Evans Electric]

Difficult to find the Reg  that actualy says that .   I just looked .

Like Lurch I've dropped shower cables down cavitys before now , and wired sockets in conservatories with fair faced brickwork.     

Is it because of the insulation  or the fact that it can't be clipped ./ supported properly . 

Bearing in mind it is more than 50mm deep 

And I admit to being told that it shouldn't be done but never really knew why.   Was told it bridged the cavity but so does insulation  and anything passing through .  Never come across a problem TBH. 

 

[Lurch]

Is it because of the insulation  or the fact that it can't be clipped ./ supported properly .

No support I think was the main issue to start with. Insulation can be accounted for and de-rated to suit as per any other type of insulation.

 

[Evans Electric]

Hmmmm   !  Would it be deemed "supported " if pushed down conduit I wonder? 

I also wonder if there is a regulation that stops us from doing anything at all . 

I heard a guy in the wholesalers recently say he'd told the customer he couldn't connect the shower in the board because it was plastic and was buying a steel board.

I asked if there were no spare ways , he says yes plenty but you can't use them can you ?

I didn't reply TBH because I'd have connected it .   In fact I did one last week . 

 

[Lurch]

I heard a guy in the wholesalers recently say he'd told the customer he couldn't connect the shower in the board because it was plastic and was buying a steel board.

I'd tell you what I would have said to him but then it would just look like I was reading off of a fruit and veg stall.

 

[Revved Up Sparky]

It still seems to be a frequent practice on new builds to feed the meter tails from the exterior meter box up through the cavity and into the back of the consumer unit on the opposite side of the wall.

 

[Adrian]

Yes but a dpc should be laid down the back of the cavity

 

[Evans Electric]

It still seems to be a frequent practice on new builds to feed the meter tails from the exterior meter box up through the cavity and into the back of the consumer unit on the opposite side of the wall.

Yes  I've done that on a couple of new builds.

 

[apprentice87]

Western power at least take a dim view of that mind....

john...

 

[OnOff]

I was always told it was to do with potential damp bridging issues but as above figured support more critical. I've dropped 20mm plastic conduit down the cavity before for outside lights and the odd socket. Figure the ribbing would offer some support. Also better that than channeling out inside.

 

[apprentice87]

WPD's main objection seems to be that; "it derates the cable" They state that it is not normally permitted...

Forgot to say; They are on about service cables though, not the tails. Perhaps they do not care about them!!

john..

 

[Lurch]

They are on about service cables though, not the tails. Perhaps they do not care about them!!

Not to that extent. If they are wrong it is your fault, that's what they care about, liability..

 

[apprentice87]

Hi Lurch,

I would definitely agree with that!!

john..