New Circuit required

[Lextoy]

We are currently constructing a loft conversion in the roof of a detached house. We have installed a new ring main because of the number of new socket outlets. We have also installed a new lighting circuit due to the number of downlighters. There would be too much loading to connect onto the existing upstairs circuits. As there is no access inside the house to run new feed cables from the cu on the ground floor up to the loft. Does anybody know the regulation concerning running one 6mm three core armoured cable from the cu out through the wall, up the outside of the house, back into the loft via the eaves and connected onto a separate cu in the loft space and fused 20amp ring and 6amp lighting with mcb's.

 

[dingbat]

Does anybody know the regulation concerning running one 6mm three core armoured cable from the cu out through the wall, up the outside of the house, back into the loft via the eaves and connected onto a separate cu in the loft space and fused 20amp ring and 6amp lighting with mcb's.

IEE Wiring Regulations Parts 1, 3, 4, 5 & 7 apply, plus all relevant parts of the Building Regulations 2000 (as amended)

 

[Taylortwocities]

And why a 20A ring?

TTC

 

[securespark]

Whether it was considered good practice or not, I'm not sure, but in the good old days, sparks used to fuse upper ring finals at 20A because they were little-loaded by comparison to the ground floor circuit.

 

[Taylortwocities]

Cor, how about that. Nothing to do with cable sizing then?

TTC

 

[securespark]

Nope. All the 20A rings I have seen have been in 2,5. I have also seen some 16/20A radials for upstairs circuits as well, but not as many as I have 20A rings.