Cable size for summer house

[thomp1983]

Hi, a neighbour has ordered a new summerhouse, he's built a nice base ready for it and is now thinking about power for it.

He plans to have a couple of sockets and some lighting in there, socket may power a small heater occasionally but will generally be a radio or TV.

To supply the power the plan is to bury an armoured cable the question is what size does it need to be and does it need to be rcd protected? The cable run will be about 18 metres will 2.5mm be ok over this distance or would 6mm be better.

His consumer unit is an older wylex unit with no rcd protection, he had a hot tub at one point and this was supplied by fitting an rcd in an external enclosure supplied from the consumer unit and then from the rcd to the hot tub, should a similar arrangement be used for the summerhouse or will the fact the cable is armoured be suitable protection, if the armour is suitable to use without rcd then it will be will be terminated into a small consumer unit with rcd in the summerhouse to protect those circuits.

Thanks
Chris

 

[Aragorn84]

When i did the summerhouse in the old place i ran 10mm SWA from a 40A switchfuse. Overkill, but it means no future worries about capacity. I used it as a workshop so wanted plenty of power for compressor/welder etc.

No RCD on the armour for me, saves a possible trip in the garage tripping the house end as well.

I wouldnt fit anything smaller than 6mm personally.

 

[RF Lighting]

2.5mm² on a 20A circuit breaker should be sufficient, but it’s only 39p per meter extra to go up a cable size. Much cheaper than replacing the cable when demand increases in the future. Maybe even go two sizes too big.

Supply the SWA from the house without RCD and then provide local RCD protection to the sockets and lights in the outbuilding.