Thread: House to shed power cable size/type

6mm may do, but I would use 10mm myself. The maximum current rating of the cable isn't enough to go on. Derate factors due to length of run, what sort of cable, single or 3 phase all need to be in the calculations, as does the calculation for fault loop impedance. If your calc says 6 is close then 10 would work fine.

You won't find 6 or 10mm in a solid conductor, it will be of 7 strand construction.

6mm

I doubt you'll even find solid, stranded is good, will be good for an easy 32A

6mm will be ample. Get it AMPle.
It will carry 32a a lot further than that

Originally Posted by Vern

6mm will be ample. Get it AMPle.
It will carry 32a a lot further than that

Thanks for your qualified answer. (Also, thanks to the other sparkies replying!)

Sounds like 6mm it is.

Gav, I appreciate there are other factors, which is why I asked the question. Factors like 3-phase don't seem very relevant to me, and since I'll unlikely be going over about 10-20A most of the time, I'm pretty happy with 6mm. In fact I may just start with a 20A RCD in the shed anyway....

..which brings me to the next technical issue! My switchboard is full!

Main switchboard in the house has 4x40A RCD's, which split the switchboard in half, each side filled with CB's. One 16A CB in the house feeds 1xBR, a few power-points in the kitchen, the dishwasher and the shed 10A RCD. The house 16A CB has never tripped. The shed one does and it's because we are definitely going over 10A trying to dry clothes and weld at the same time.

Assuming that I'm loading the 2x40A RCD's evenly in the main switchboard, is an appropriate solution to replace the 16A CB with a 32A CB still feeding the 1xBR, a few power-points in the kitchen, the dishwasher and the shed 20A RCD via my new cable run? I.E. Effectively 2 cables/circuits being fed out of the 1 CB in the house.

Doesn't your electrician know ?

If you are planning on installing machine tools, get three phase 415 v. power installed. Used 240 v. machine tools sell at a considerable premium over three phase machines.

Originally Posted by Brian Hjelm

If you are planning on installing machine tools, get three phase 415 v. power installed. Used 240 v. machine tools sell at a considerable premium over three phase machines.

Scope creep!

Really the main requirement at the moment is to be able to run both the drier and washing machine at the same time! But instead of just changing the shed RCD from 10A to 16A - which would probably work - I'm looking a little past that and allowing for maybe a 15A outlet in the shed or just generally allowing for a bit more power if needed. But nothing really major.

Originally Posted by Judo

Main switchboard in the house has 4x40A RCD's, which split the switchboard in half, each side filled with CB's. One 16A CB in the house feeds 1xBR, a few power-points in the kitchen, the dishwasher and the shed 10A RCD. The house 16A CB has never tripped. The shed one does and it's because we are definitely going over 10A trying to dry clothes and weld at the same time.

A suggestion would be to replace all circuit breakers where possible with single gang RCDs which would free up a couple of spaces by removing the older style RCDs which feed multiple breakers.