Armoured cable junction box

[Farmer Giles]

I could do with a bit of advice/help from any of the electricians on the group (Adam, are you about?).

I have a shed at the rear of my garage that is fed by an armoured cable from the house CU. The cable runs along the wall of the garage, and I want to tap into it to give me a supply to the garage. Obviously I needed a junction box, which I got from Screwfix:

The problem is that I'm not sure that this is actually what I need. The box seems a little heavy duty, to say the least, and inside it is just an empty box - no terminals or anything (apart from an earth ring) - what are you supposed to connect the conductors to? Having spent £23.50 for a junction box - which is what Screwfix call it - I expected to just cut the cable, fit the glands, and have a three-way junction giving me a garage supply. Anyone used these things, or can advise me on the best way to connect the conductors?

Thanks.

[Andrew Gabriel]

You can use chocolate block connectors inside the box. Unless you can pull a tiny bit of slack, it's going to be tight though.

However, it doesn't look from the picture that the glands are SWA glands (although it's difficult to see, and if they aren't, then I don't understand why there's an earth ring supplied). The glands you want for SWA outside are usually called CW20S, which is Screwfix part

There may also be provision for a small condensate drain hole in the bottom of the junction box, which might need drilling out (unless the box is going underground or might get submerged).

[Palindr☻me]

IANA domestic wiring electrician...

IIUC:

Part P means that all external mains wiring alterations need to be done by either a Part P self-certifying electrical installation company or in liaison with the building control dept of your council. It will need to be inspected and certified.

Shame you hadn't done this a year or so ago, when it was quite legal to do your own wiring. Back then, you might have used normal terminal blocks rated for the current. You would have needed to make very sure of strain relief of all the cables and been very, very careful about earth continuity.

Of course, if the house end of the armoured cable is simply plugged in a wall socket, Part P doesn't apply as it is a temporary circuit and not an installation..

Bear in mind that the new seller's pack does, IIUC, have to include an electrical installation certificate. So any wiring alterations done after Part P became effective would have to have their own certificates and the electrician doing the seller's pack inspection would expect to see them. Of course it would be quite hard to tell when a particular wiring alteration was done, especially if old colour code cable was used. With new colour code, there was a small window when it was available before Part P took effect.

[Farmer Giles]

Thanks for that, I would have preferred something better than chocolate block connectors though. I put this armoured cable in myself a couple of years ago, and made provision then for this junction, so the cable length is ok.

I think the glands are SWA glands - but I do have the other type anyway.

The box is to be fitted on the wall - about 6 feet off the ground - so I will check out the drainage hole.

Many thanks.

[Farmer Giles]

I appreciate your very sound advice about Part P - which I am very aware of, but not too concerned about. Like you IANA electrician, but I have many years experience in working on industrial control systems and the like, so I am used to dealing with electrical/electronic systems. This armoured cable was installed by me a while back, with provision to connect to the garage at a later date. The garage did have a supply from the house, which I am not happy with (installed by the previous owner), so now that I have rewired it - with its own separate CU - I just need to tap into the 4.0mm SWA going to the other outbuilding (hence my question).

No it is connected to the house CU.

You are correct, but I don't intend to move in the near future. Even if I do I don't think it could easily be proved that any of this wasn't done before Part P came into force.

[Mackem]

Well at least you were right about the World Cup !!