Bungalow board change

[Pretty Mouth]

Have had an estimate accepted for a CU change in a 1980s bungalow. I based the estimate mainly on an EICR which was carried out on the property by another spark last summer, plus I had a quick look at the existing board, meter, and bonding.

The EICR has all circuits listed as ref method C, but I suspect there's a good chance it'll actually be method 101 - I expect cables for all circuits to be under insulation in the loft. Ok, no problem for the lighting circuits on 6A breakers, but the CCC of the 3 ring finals (2.5mm = 17A) and 2 cooker circuits (6mm = 27A) would be too low for 32A breakers.

Assuming that the cables are in good condition, no signs of thermal damage, what do you guys and girls do in this situation? Derating the breakers is one option, but could lead to nuisance tripping, at least for the kitchen circuits. Putting the cables in conduit is another, but it's a lot of itchy work up there that I'd like to avoid if possible, and will add a lot to the price.

 

[pc1966]

Any option for 25A RCBO for your chosen board? Would safely do both circuits.

But try to check the loft cables first, as if method 100 then should be fine on the usual 32A.

 

[Pretty Mouth]

Any option for 25A RCBO for your chosen board? Would safely do both circuits.

But try to check the loft cables first, as if method 100 then should be fine on the usual 32A.

Thanks @pc1966 . Yes, it'll be a Hager RCBO board so 25A are available.

I had considered 25A for the rings, based on the old ratio of cable rating => 2/3rds of the breaker rating. Anecdotally, this was changed to cable rating => 20A, to allow 32A breakers to protect rings installed to the same installation methods as those protected by 30A fuses.

 

[littlespark]

Apart from the kitchen, the sockets won’t take anything near 25A never mind 32....
Although they might have a lot of plug in heaters, hot tub etc