Outside power supply

[sparkybird]

Hi there

A friend of mine is wanting to install some outside power sockets in his garden for lights, lawnmower etc. I have suggested that he needs to get this done professionally, but he is is going ahead anyway, so I want to give him some advice so he doesn't kill himself!

Can you just clarify a few things for me?
1. It's quite a long run (30m), so I'll check the voltage drop - but does this 'start' from where the spur will come off the ring or do I have to start it from the CCU?
2. I'm not sure if his ring is on an RCD, but if not, should only the first outside socket be RCD protected or does each one need to be?
3. As it'll be a spur off an existing inside socket, I reckon that the first outside socket (spur) also needs to be a fused one
4. I'm gonna suggest 3 core SWA for the cable

Hope you can help
SB

 

[mapj1]

Well, it should start at the CU as the voltage drops will accumalate, but what is going at the end - does he care if the shed lights flicker a bit as the lawnmower is used.
30m ...Hmm... 4mm, 13A fused spur as a radial, and RCD.
2.5mm might do it too but I think the cost advantage is small, and the digging is the same.
agree on use of three core - and point him at the recent thread on wiring SWA glands - good how (not) to do it pics.

 

[sparkybird]

Thanks mapj1.

Just been looking at suppliers and it's not clear to me if an RCD protected outside socket is also fused. I think not, so would he need to put in a 13A FCU between his inside socket and his first outside socket to protect the radial so to speak? I've also discovered that you can get an RCD Spur combined so this might be even better??

Any advice would be really helpful!

SB

 

[sparkybird]

I'm OK at SWA, so can show him that - but it then just occured to me that the socket boxes will need to be metal - or will they, as he's not using the 'armour' as the earth? Or is it difficult to terminate SWA into a plastic box??

Maybe I shouldn't have offered to help - this is giving me a headache!

SB

 

[mapj1]

SWA into plastic boxes can be done, but the tail tends to wag the dog, and some thin wall boxes are a bit weak for this. Much nicer to use metal boxes - even if its metal conduit type box with plastic box along side.. Even with three core, please do earth the armour, otherwise a large part of the protection against garden forks etc is lost.
If its coming of the ring, he will need to turn it off for holidays and maintainence and leave the ring on indoors- I'd suggest an indoor RCD spur is a good idea, unless his ring is already on an RCD I'd also suggest a double size box and blanking plate to hold the wiring in. if bringing the SWA directly into the back of an indoor box.
Mind you, I'd wait for other responses - I've only given this about 10 seconds.

 

[comms]

Check the cu to see if you could replace existing mcb & use an rcbo to provide rcd & overcurrent protection to the whole circuit.

 

[Spark123]

Don't forget all your outside accessories must be waterproof or mounted as to not allow ingress. All of the outside socket outlets must be RCD protected which makes me think one of the RCD FCU is more viable unless the CU already has an RCD. The first socket does not need to be a fused one as there will be a fuse in the (RCD) FCU.