running power to a summer house.

[ZETEC153]

hi

i want to run power to my parents summer house. There is an enclosure on the frame work at the end of the pergola which is fed by 2.5mm SWA which was installed when his workshop was built. First question is is 2.5mm man enough to run workshop?? He runs saws, drills, planers etc but never all at once plus lighting!!

With regard to the cable supplying the enclosure, is it ok to fit an RCD at the junction and carry on the run (approx 20m) under ground and up into the summer house in 2.5?? i wanted to use 4mm and know that you need protection where the cable size changes.

It will be supplying a small Hager CU with 63A main switch, 63ARCD, 6amp MCB for lights, and 16 or 20amp MCB for sockets.

many thanks

 

[Steve]

You only need ONE RCD. You are gaining nothing by having 5 RCDs protecting the same outlets.

What is the length of run to this enclosure? Are you saying this enclosure acts as a junction box where another cable exits and supplies the workshop? And you want to tee off this?

What will be the total length to both workshop and summer house?

 

[ZETEC153]

You only need ONE RCD. You are gaining nothing by having 5 RCDs protecting the same outlets.

What is the length of run to this enclosure? Are you saying this enclosure acts as a junction box where another cable exits and supplies the workshop? And you want to tee off this?

What will be the total length to both workshop and summer house?

the enclosure is fed from the main CU in the house. The workshop is fed from the CU in the house. The workshop is all wired up on its own cable.

The enclosure is basically where the original electrician ran the cable underground and up the pillar and terminated it 'for future use'. I want to carry on this cable into the summer house. Am i right in thinking i need some sort of protection at this junction?? hence the RCD at the junction. So i can just have one RCD in the CU in the summer house, and the 2 MCB for the lights and sockets. Do i need the main switch or can i run the supply through the RCD?? The Hager unit i want to get comes with a 63A main switch.

The total length to the summer house from this enclosure is approx 20m. I would say from this to the CU in the house 30m, so say approx 50m in total from original supply point.

was also unsure about how to earth it properly, as its a bloody good run for the earth canle back to the CU in the house!!!

cheers

 

[Steve]

You will be ok with the earth from the house, as long as the summer house has no ECPs (metal structure or water, gas or drain service).

You dont need any protection at the junction box. As long as its the same cable. You would be best fitting the RCD in the house. In fact, is the cable run already RCD protected? If it is, you dont need another.

You can replace the Hager's mainswitch for an RCD if you needed to, by the way.

50 metres is a long way, and according to TLC's calculator that 2.5mm² will only be good for about 10 amps. But then again its only a summer house, maybe a light and a tv, dont go running any heaters in there, unless its only 1kw.

 

[flameport]

2.5mm cable over 50m will be virtually useless. The voltage drop over that distance will limit you to a tiny load.
4mm or probably 6mm would be more likely, for the whole 50m length.

2.5mm for the workshop is probably undersized already.

 

[spark1]

--------------------------------------------------------------------------------

hi

i want to run power to my parents summer house.

You have notified your local Building control about your intentions then ?

 

[ban-all-sheds]

Steve, flameport - do you honestly believes that someone who thinks you need "protection" where a cable increases in size, and that an RCD would provide that protection is OK to install a CU?

Zetec - you really don't know or understand enough to be tackling a job of this magnitude. It's all very well coming onto a DIY advice site and asking questions to help you do some jobs, but there is too much involved in this one for that to be a workable idea - what if you don't ask about something important because you have no idea it exists? And it's clear from your muddled "knowledge" about "protection" that there are big holes in your understanding.

If the job can wait until next summer then you'll find plenty of information, and pointers to information, on this site which will enable you to learn what you need to learn, but if not then please get a registered electrician. Not only will this be safer, there's a good chance that it will be cheaper, given the Building Regulations requirements.