Wall insulation

[markadams]

Just first fixed a house where I was initially told that the external walls were going to be battened then boarded, I used metal capping over the 2.5mm T&E ring final circuits on the external walls and chased the internal ones into the wall with 20mm oval conduit.

I have now been told that the external walls are going to have 65mm wall insulation dot and dabbed on the inside.

Would you up-rate the cables, de-rate the protective device or just leave it as is? about 1/4 of the sockets are affected.

 

[littlespark]

Rerun all the affected cables as you would have done if you had known, then charge them as an extra.

 

[Vortigern]

So if you re-run your calcs, especial attention to Ci what is your result. I think you get for 100mm derate to .89 (.81 for 50mm) which on a ring is acceptable at 32a personally. But that is based on the idea you have two 2.5. If it was a radial at 20a again I think good to go.

 

[markadams]

Its 0.88 for 50mm and 0.78 for 100mm

523.9 specifies that if the cable totally surrounded by thermally insulating material over a length of 0.5m or more then a rating factor of 0.5 is used.

My problem with this is that the cable is not totally surrounded by thermal insulation so this doesn't apply.

 

[Pretty Mouth]

My problem with this is that the cable is not totally surrounded by thermal insulation so this doesn't apply.

I'd say this sort of fits ref method 102 - in a stud wall with thermal insulation with cable touching the inner wall surface. True, the cable is touching the outer wall surface rather than inner, but the outer wall is generally going to be a lot cooler than the inner wall anyway.

 

[markadams]

I'd say this sort of fits ref method 102 - in a stud wall with thermal insulation with cable touching the inner wall surface. True, the cable is touching the outer wall surface rather than inner, but the outer wall is generally going to be a lot cooler than the inner wall anyway.

Reference method 102 is not a perfect match but the closest to the situation, if this this correct then given that a 32A must have a capacity of at least 20A per leg this would comply as Ref method 102 gives 21A for 2.5mm csa T&E.