External sockets

[matthew.larkin]

Before I start, please feel free to point out that I should not be doing this if I don't know what I'm doing, and it is sound advice which I may follow. However, I might be tempted....

I've currently got a taped off live mains cable in the hall (well out of the way, insulated, terminated in a junction box) which was previously used as the supply for a burglar alarm (no longer required). This is fed from one of the mains circuits in the house (presume it is a spur).

Wife would like a couple of external sockets just outside the front door, and reusing this spur would seem the obvious answer. I presume I would need some sort of isolating switch inside the house, and (obviously) properly approved sockets on the outside.

Is there anything else which I would need to take account of?

Matt

[Lobster]

You ought to confirm that for definite. In particular, is it definitely appropriate cable for a socket, and it's not either too small and/or is derived from a lighting circuit or something horrible?

If it's indeed a bona-fide spur, then you can only fit one socket to it (but including one double socket), so you need to check there's not already one wired to it. AFAIK there's no regulatory need to specifically have an isolating switch other than the need to prevent others from 'stealing' your electricity, if that's a perceived risk.

David

[Dave Liquorice]

Agreed.

You also need an RCD on any external circuits. This could be one of the (expensive) weather proof jobbies or one inside mounted on the existing wall box, if that is what the OP has. What does the OP really mean by "junction box"? A round flat thing with termianl inside or a surface or flush wall box that a standard fitting would mount onto. I'd go for the inside option as you can then isolate the external sockets when not in use and they are cheaper. You would still require exterior/weather proof socket for outside though.

[dom]

External sockets should be RCD protected.

Burglar alarms supplies shouldn't be.

A good burglar alarm install would have been on it's own non-rcd circuit, and not spurred off the ring main - double check whether your is or isn't.

Also look at weatherproof sockets.

This would be a good solution to an outdoor spur from a non-rcd protected ring main:

[The Natural Philosopher]

No. but it should be on an RCD protected ring. May need RCBO on that ring. Check it isn't on a LIGHTING circuit.

and

Pay great attention to keeping the socket in a dryish place, and use mastic to seal all holes through which cables pass.

[Lobster]

And drill the hole through the wall so it slopes slightly in the outward direction so if the worst comes to the worst, any ingress of water won't track into the house.

David

[The Natural Philosopher]

VERY good point..

[<me9]

It also needs RCD protection, preferably independent of other circuits. If an RCD is fitted internally then it can be used to switch off the supply to the socket.

Then there's Prat P.

[matthew.larkin]

Thanks one and all, good advice I'm sure.

I'm certain its not on a lighting circuit (switched off the lighting circuits at the CU to test), though I do need to trace it back to the CU to find out what it is actually on.

Water ingress won't be an issue as the external socket will be in a covered area behind some plant pots, so shouldn't even get wet on a windy / raingy day either. But drill downhill from inside does sound like common sense at least!

Is there a *requirement* for RCD protection, or is that just best practice (being in mind that wife and I always use a plug in RCD when working with external stuff such as hedge trimmers or lawnmowers).

I would put a fused switch inside there because for part of the year it would power the external Christmas lights (!) so being able to switch them off at night easily would be desireable.

Cheers!

Matt

[The Natural Philosopher]

Yes.I've tripped mine twice already with extensi cables left in the rain.. DO IT.

As someone else mentioned, may be able to integrate this with the isolator switch.

Good point.

[dom]

Yes, RCD protection is a requirement of the 16th wiring regs for any socket that *may be* used for external appliances.

You have also checked the conductor size on the wiring up to the junction box is correct for a spur?

BTW if it is a dedicated alarm circuit, rather than a spur off the ring, it may only be fused at 6A.

[Dave Plowman (News)]

Yes - unless already RCD protected in the CU. Applies to any outdoor socket or any likely to be used for outdoor electrics. Which is rather a broad canvass.;-)

You can get 1 gang flush mounting RCD spur units which also provide a convenient way of isolating the outdoor socket if sited in a reasonable way.

[Andy Wade]

There is a very _definite_requirement_ in the wiring regulations for

30mA RCD protection for all sockets that can be expected to be used to supply portable equipment outdoors [regulation 471-16-01]. This is very firmly established and you would be seriously negligent if you ignored it, IMHO.

[Lobster]

Check your Xmas lights don't have a transformer between the plug and the lights which is not rated for external use though - plenty are intended to be plugged in inside, with only a low-voltage cable going outside.

David

[matthew.larkin]

(Don't tell the H&S reps but) they have wall-wart transformers on, which I will quite happily allow outside as the proposed socket site is well protected from the elements. A temporary installation of a plastic bag will also tranditionally be applied over the transformers (as used in previous Christmases at the rear of the house).

Correct me if I'm wrong here, but the likelihood of a wall-wart transformer being "attacked" by the weather and turning itself into a

240v death trap is unlikely?

Matt

[Huge]

I've bought fused spurs with RCDs built in for the sockets outside the front and back doors, and keep them tripped when not in use.

(Anther reason to keep them switched off - you don't really want Joe Burglar using your electricity to cut a big hole in your front door, do you?)

[John Rumm]

Once you have established that the spur is off a non rcd protected power circuit[1], you could fit a RCD spur inside:

a suitable external socket outside:

You don't want an external socket sharing a RCD with internal circuits since there is increased risk of it causing nuisance tripping.

more detail on outdoor electrics in general try here:

[Andy Dingley]

CU should be a 100mA RCD

The requirement for outdoors is a 30mA

[Andrew Gabriel]

or a proper outdoor cable system with waterproof glands.

Don't forget to drill a condensate drain hole in the base.

[Andrew Gabriel]

Another reason to fit the RCD indoors is that it's an expensive part of the installation, and it's easily destroyed by moisture (even from condensation due to temperature changes) outdoors.