SWA Size

[New2Game]

What size SWA will be needed to feed a 40A RCD Garage CU?
Should this be fed from DP side of split-load board (as protected once in garage), or RCD side?
It will be run under floor cavity, then buried under concrete when outside. The run under cavity will be 10M and outside 4M.

 

[industryspark]

Personally id feed it from non rcd side of s/l board and rcd the sockets in the garage. more convenient if it trip- can reset in the garage and not have to finf your way back to the house in the dark.

you'l have to do the cable calcs refering to the regs for the cable, what efli do you want at the sub main...etc

off top of head though it seems like a 6mm job although you may get away with 4, you'l have to check. id also go higher to give future proofing.

 

[New2Game]

What reference method will it be if buried under concrete? If only buried for less than 1/4 of run and clipped in floor space for the rest, would i still be best taking buried into calc? Would it make much diff?

 

[industryspark]

my regs book is at work and i cant remember the reference off hand, have a look in bs7671-they're pretty self explanatory.

i would take cable being buried into the calc yes. as for whether it'l make a difference , probably not but do it anyway. stick to the regs and your covering your back

 

[New2Game]

How deep does the SWA need to be buried, is it 600mm?

 

[industryspark]

its 500mm i believe, you should also put some warning tape above the cable so people digging know what to expect if the situation ever arises.

you could also consider using ducting or tubing set in the concrete to allow for drawing the cable in- could come in handy if it ever needs replacing (unlikely i know)

 

[ricicle]

450mm deep
Method 1 (cables buried directly in building materials)

4mm² = 49A single phase, 12mV/A/m drop (XLPE)

Hope this helps