Extend 16A Radial with 1mm T&E?

[endecotp]

The cable does pass through the cavity wall between the garage and the house. The cavity is around 70mm so the cable will be surrounded by insulation for that distance - I'm not sure if any derating needs to be applying for that distance?

Yes, you should derate for that.
My 17th ed OSG table 6B gives a derating factor of 0.78 for 100mm of insulation with thermal conductivity greater than 0.04 W/mK. But most modern insulation materials are at least a bit better insulators than that. 50mm is 0.88.

 

[JohnW2]

Thanks. I stripped a short length of 1.0mm² and 1.5mm² to check my caliper and they measured at 1.14mm and 1.36mm respectively - not quite perfect but certainly within the realms of an uncalibrated "domestic" caliper!

Those measured diameters are very close to what 1.0 mm² and 1.5 mm² cable should be.

Kind Regards, John

 

[imroberts]

Yes, you should derate for that.
My 17th ed OSG table 6B gives a derating factor of 0.78 for 100mm of insulation with thermal conductivity greater than 0.04 W/mK. But most modern insulation materials are at least a bit better insulators than that. 50mm is 0.88.

Ah yes, thanks. So sounds like I ought to fuse down - if we assume a derating factor of 0.78 that only gives me 12.48A so I'd need to fuse down to 10A.

In the spirit of being over-cautious I think I might just connect the new socket to the load side of the existing 3A FCU until such a time as I can replace the 1.0mm with 2.5mm then I can simply move the socket to the supply side as I'd like. 3A is more than enough for what I plan to use it for in the meantime.