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Insulation and thermal bridging and an EV charger

JohnE

The situation is a garage being converted into a TV room

External wall with batten attached which is to be insulated with 75mm PIR insulation and plaster boarded
Stud is only 70mm!!

Picture attached...

The house CU is high up on the wall. the tails ran down the internal garage wall to the outside meter box
A second CU was mid way down the wall feeding  an external EV charger, the tails of which also went to the external meter box

The tails were in plastic conduit surface mounded.

Since the tails (no RCD protection)to both boards are to be hidden by the plasterboard, I though best to put in two lengths of earthed metal conduit (50x50)
The 10mm feed to the 7kW charger is clipped to the batten.

The owner is doing the batten and insulation.
I am concerned about insulation being near my cables and trunking


I presume the trunking it self will be a break in the insulation so could be a thermal bridge?

Could you run the insulation up to the trunking or should they be a gap.

cables clipped along the batten how far should they be from the insulation,
I would like to leave about a 50mm gap? but this will cause this thermal bridge issue I believe?

Also say if  a 2.5mm  socket radial (fused to 16A) was ran through the batten and against the concrete block 
with insulation over it. What installation method would you consider that. I presume these soft concrete blocks have some insulation factor.
Will they be much of a heat sink?

I am concerned about the EV cable really as a continuous load in this stud work. Its has a bit of extra capacity as 10mm2 for a 7kW charger.

How can the wall be adequately insulated, without bridging and the cables be safe?

Thanks

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  • 0

    I dont thnk metal trunking has enough mechanical protection to allow the cables contained within it to be non RCD protected. the usual answer is 2mm of metal for mechanical protection, though I dont think 20mm conduit has a wall thickness of 2mm, but it is certainly a lot thicker than metal trunking.

    I reckon earthed  steel trunking is OK in that respect - it doesn't, as you correctly say, provide adequate mechanical protection, but it does provide protection by guaranteeing ADS should anything metallic pierce through to a line conductor (in much the same way as for BS 8436 cables, or indeed SWA - as it's dead easy to force something sharp between the strands of the armour).

    Regs wise, it meets 522.6.204 (iii), rather than (iv).

       - Andy. 

  • 0 in reply to AJJewsbury

    and, if it is more than 50mm below the celotex, cable is out of zones anyway. 

    It would be better in terms of cable rating if the tails could use the blockwork as heatsinking. It is probably not so good from a room thermal and condensation damage perspective.

    Mike. 

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  • 0 in reply to AJJewsbury

    and, if it is more than 50mm below the celotex, cable is out of zones anyway. 

    It would be better in terms of cable rating if the tails could use the blockwork as heatsinking. It is probably not so good from a room thermal and condensation damage perspective.

    Mike. 

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