spring from an existing SWA cable

[gordon daly]

I have a 10mm existing armoured cable from CU on a 40A MCB going to workshop CU already in place. Also the shed is wired up and max draw estimate is less than 2Kw.

My question is what are the rules for adding a power circuit spur from the armoured cable junction box.
Specifically, The 10mm SWA 3 core terminates at a IP66 junction box outside the house. from there it is internal flat 10mm twin and earth to the main consumer unit on its own way with a 40mm MCB.
I would like to spur from the junction box outside the house to an external socket (x2) over a distance of about 8M from junction to last socket. I was planning to use 2.5mm external 3 core NYY-J Cable Black with appropriate glands, clipped to wall.
Firstly, must this be a 13A fused spur? and what are the other considerations for this setup as I'm having trouble finding specific info in the regs or online.

 

[ericmark]

Your looking at something like this

which is filled with epoxy resin, but it can be done, however not really a DIY job.

 

[JohnW2]

I would like to spur from the junction box outside the house to an external socket (x2) over a distance of about 8M from junction to last socket. I was planning to use 2.5mm external 3 core NYY-J Cable Black with appropriate glands, clipped to wall.
Firstly, must this be a 13A fused spur? and what are the other considerations for this setup as I'm having trouble finding specific info in the regs or online.

That somewhat depends upon what you mean by "an external socket (x2)". If you are talking about two single sockets, or one double socket, then the 2.5mm² cable should be fine without it being a 'fused spur' (since the 2.5mm² cable is able to carry a 2 x 13A load). However, if there were more than two socket outlets (i.e. more than two single, or one double, sockets) then it would either have to be a 'fused spur' with 2.5mm cable (which would limit you to a total of 13A across all the sockets) or else would have to use cable which would be adequately protected by the 40A MCB (which would probably mean 6mm² cable).

Any new sockets are required to be RCD protected. Is the circuit in question already protected by an RCD in your CU?

Kind Regards, John

 

[JohnW2]

Your looking at something like this which is filled with epoxy resin, but it can be done, however not really a DIY job.

As I understand it, he intends to take the feed to the new sockets from the existing JB (where the SWA interfaces with indoor T+E) - so he doesn't need to 'split' the SWA (or any other cable).

Kind Regards, John

 

[gordon daly]

hi john,

Thanks very much for the reply. yes its 2 x double sockets with a possible 3rd double in the future for a terrace lamp. no heavy use intended from any of the sockets. Yes its an RCD protected circuit. Also, as you say, its from the junction box at the SWA / indoor T+E interface

So from what you say it looks like junction box to 13A fused unit and then to the 2 x double sockets all external on the rear of the house?

Thanks,

gordon

 

[AndyPRK]

Cant you just drill out of an existing socket and put a socket on outside wall?

 

[JohnW2]

hi john, Thanks very much for the reply. yes its 2 x double sockets with a possible 3rd double in the future for a terrace lamp. no heavy use intended from any of the sockets. Yes its an RCD protected circuit. Also, as you say, its from the junction box at the SWA / indoor T+E interface. So from what you say it looks like junction box to 13A fused unit and then to the 2 x double sockets all external on the rear of the house?

Yes, that sounds about it - and is fine so long as you will never need more than 13A (in total) from the new sockets. It would be nice to avoid having an exterior FCU (yet another possible source of water ingress), but that may be the most practical/convenient way - unless you could take the feed from the JB back 'indoors' (and then back out again to the new sockets) (or even intercept the current indoor feed to the JB) and so be able to have the FCU indoors.

However, as Andy has suggested, have you considered supplying the new exterior sockets in some other way, such as he suggests? Just because you already have one supply 'going outdoors' does not compel you to use that for the new sockets.

Kind Regards, John

 

[gordon daly]

unfortunately there is no circuit inside the rear extension that is accessible. but no worries, thanks very much to all of you for your help.

kind regards,

gordon