I've got an extension which has been dry lined with timber stud work and plasterboard and the gap between the wall has been stuffed with loft insulation. The electrical cable for the sockets is running down from ceiling level and clipped against the solid wall but the insulation is ontop of this. Is this ok?
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Cables in dry lining insulation
- Thread starter tireetim
- Start date
With that method of installation 2.5mm² cable is derated to 21A so not a problem on a Ring circuit - or a Radial circuit protected by a 20A mcb.
The key to this is the word "insulation", cable can get warm near full load and the makers tend to give it a operating temp in open air (which will have a cooling effect).
So a cable not in open air tends to need derating, insulation being one such derating category. Others include in trunking, conduit, in plaster.
There also derating for grouping, so a bundle of cable together will also require a derating factor.
So a cable not in open air tends to need derating, insulation being one such derating category. Others include in trunking, conduit, in plaster.
There also derating for grouping, so a bundle of cable together will also require a derating factor.
@tireetim
I get that as Ref method 103 which would cut it down to 13.5A
I get that as Ref method 103 which would cut it down to 13.5A
I'd have said no. Its the being attached to the boards / stud work that allows it to dissipate the heat. Who's to say that your nicely cleared hole doesn't collapse back in on itself and enclose the bottom 2/3's again?
Ref Method A (enclosed in conduit in an insulated wall) will push the rating back up to 20A (airspace around cable). Whether this can be plastic conduit I'm honestly not sure! But that would keep the insulation away from it.
You don't need to keep the insulation away if, as said, the cable is clipped to the wall.
I'd try the conduit method, if you can get it in!
Otherwise 4mm cable would give you 17.5A and 6mm cable would give you 23.5A
Otherwise 4mm cable would give you 17.5A and 6mm cable would give you 23.5A
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