Cable rising 35mm to sockets / insulated plasterboard - derating required?

[SJRSJR]

Hello

I was planning on putting insulated plasterboard on an external bedroom wall, but I came across a reference to derating the electrical circuit if cables are encased in insulation, so I thought I'd check to see how this might affect things.

The external wall is plastered brick cavity and there are two double sockets on the wall. It's a ring circuit which includes two bedrooms, the landing and a bathroom. The sockets are 35cm above the floor, the rest of the cable is below the floorboards lying loose on the back of the lath and plaster ceiling below, with approx 9 inch joists, no insulation. Where it runs down the walls it'll either be behind lath and plaster or plastered in, I'm not sure. I checked an EICR report from when it had a new CU in 2022 and it says it's a 32A circuit with 30A RCD protection, (the invoice refers to RCBO).

Does derating apply to small runs or does it average across the length of the run? (A generous estimate of the circuit would be 30m). And if no/ minimal derating is required, is there a way to fit the socket to avoid the potential for overheating? Thanks

 

[EFLImpudence]

Insulation derating applies to just the length of cable affected by it.

How thick is the insulation through which the cable will run?

 

[EFLImpudence]

 

[EFLImpudence]

You already have 0.75 derating covered by the standard ring circuit arrangements.

 

[Taylortwocities]

It will be fine. Crack on.

 

[SJRSJR]

Thank you both. That's a relief.

I hadn't got so far as to the thickness of the insulation but it's a smallish room so probably not more that 60mm