Discuss Summerhouse Wiring Debate in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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Morning all,

I've been having a debate with someone I know who wants their summerhouse wiring up. The summer house is approx 25-30M from the CU in the house and they will want 2/3 x double sockets and 2 x lights (internal & external).
The double sockets will power a small wine fridge/cooler, radio or sound bar, a neon sign and maybe one or two more small appliances that they're unsure of at the minute.

The debate is about the csa to feed the summerhouse. He said that there is a length of 2.5mm SWA 4 core that runs from the house to where the summerhouse is now, buried in a duct as it used to feed some sort of pump for a pond that was once there. He would like to reconnect the 2.5mm SWA to the CU in the house and then to the sockets in the summerhouse, and spur from them for the lighting.

I on the other hand believe that the feed should be upgraded to atleast a 4mm SWA from the CU in the house, to a small CU in the summerhouse, and take the final circuits from there. I just think that even if you were to connect the 2.5mm SWA to a CU in the summer house, that the CSA is just too small. Do you agree?

Although the latest edition of BS7671 says that the current carrying capacity of 2.5mm SWA is 29A direct in ground, the 37A for 4mm SWA just gives you that extra room.

I'd appreciate any advice and input on this one.
 
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I'd say why not please the customer and get the job. Although it's not the way you would like to do it, it does seem sensible to keep on good terms with your customers. Just run it on a 20amp mcb with a fused spur for lighting.
 

davesparks

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As long as the 2.5mm is appropriately protected I see no problem.

You don't necessarily need a CU at the summerhouse either, if its a 20A circuit it could feed the sockets directly with a sfcu for the lights. You'll just have to find a way to provide the necessary RCD protection
 

Wilko

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If they need more than 20A then maybe upgrade, but a summer house where the biggest load is the kettle should be fine.
 
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  • #6
Thanks for the replies I appreciate the feedback!

I was just more concerned with future proofing the install, as it's all well and good them saying they'll limit the use of appliances but we all know how things can change. Maybe I was being too over cautious afterall.

As long as the 2.5mm is appropriately protected I see no problem.

You don't necessarily need a CU at the summerhouse either, if its a 20A circuit it could feed the sockets directly with a sfcu for the lights. You'll just have to find a way to provide the necessary RCD protection
The CU in the house already has RCD protection, and some spare ways, so I would be sorted for that one thanks. I forgot to mention that in my original post.
 
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  • #7
Double up the cores?
As in use two cores as the live, one for neutral and one for earth.
Or two cores for live, two for netural and the armouring for the earth.
Would I be right in thinking that you take the value of ccc for 1 three or four cable x 2 x 0.9 as a derating factor?
 

davesparks

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I was just more concerned with future proofing the install, as it's all well and good them saying they'll limit the use of appliances but we all know how things can change. .
How can you 'future proof' it? Do you have the ability to see into the future and know what is going to happen? And how far into the future would you be proofing it for?
 
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  • #15
How can you 'future proof' it? Do you have the ability to see into the future and know what is going to happen? And how far into the future would you be proofing it for?
If I take a larger feed, to a CU with multiple ways, then there's plenty of room for expansion in the future. How many times have you heard of someone wanting to add something later on but there being no room in the CU or the csa is inadequate.
If they want to add some more sockets, add some more sockets. Need some heating in there in the winter? Plug in some heaters. You want to plug in a inflatable hot tub? Plug in that hot tub. Sorry not sure what you didn't get when I said future proofing the install..
 

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