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?
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 http://www.screwfix.com/app/sfd/cat/pro.jsp?id 877&ts 838
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).
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.
IANA domestic wiring electrician...
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
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
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.
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
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.
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