UK Power to shed

Sam2001 · Nov 14, 2020

There is a fuse spur switch from the ring main, this spur feeds a two double sockets as a radial to the shed, is on 2.5mm flex in conduit underground. (Installed by Council Electrician)

What I want to know is; can I use the fused spur to power a CU and run a lighting circuit as well as a ring main/radial from this in the shed?

Wasn't sure if I could change the 2.5mm flex to a 4mm or 6mm as main power to CU (40A main breaker?) And run a 32A ring main/20or16A radial circuit and a 6A lighting circuit.

But then was wondering if I can do i need to up the fuse size in the spur? Its physically impossible to run a new cable from the existing CU in the house...

Long story short; I would like lights included in the shed, and want to know if I can use the fuse spur to power a CU to run my circuits from.

westward10 · Nov 14, 2020

You are limited to the 13A fuse at the spur so installing a CU is pointless. Fit a spur from one of the shed sockets with a 5A fuse for the lighting.

Sam2001 · Nov 14, 2020

westward10 said:
You are limited to the 13A fuse at the spur so installing a CU is pointless. Fit a spur from one of the shed sockets with a 5A fuse for the lighting.

I thought spurring from a spur was bad practice? Regardless of them both being fused? Didn't think to mention it due to this?

Burtones · Nov 14, 2020

Sam2001 said:
I thought spurring from a spur was bad practice? Regardless of them both being fused? Didn't think to mention it due to this?

A spur only applies to a ring final circuit and yes you cannot spur from an unfused spur- but in this case, the spur is a fused connection unit and you can branch off as many times as you like without overloading the cable due to the 13A fuse.

If it was a radial circuit, then the concept of a spur doesn't really exist and you can branch off in any direction from any point.