I'm intending to run a power feed out to the garage soon. The route
will be straight through the wall from the under stairs cupboard to the
outside, up the wall approx six feet and then horizontally to the corner
of the house. From there it will go along the top of a short fence/gate
(about 10 feet) and through the garage wall.
The plan is to run a 4mm armoured cable for this, fed from a 32A MCB and
terminating it in a small CU in the garage. I did look at Hituf but
it's about twice the price... The plan is to move the freezer to the
garage so the garage CU will have a 16A MCB for that, a 6A MCB for
lighting and a 16A RCD for general power.
1. Is this arrangement allowed? A google search brought up some post
earlier this year about outbuildings being fed TT and not using the
house earth. This scuppers the freezer plan!
2. How do I make off the ends of the armoured cable? The house CU is
plastic so obviously I need to run some 4mm T&E from there into a metal
box and join it to the armoured cable. Are the gland kits fairly self
explanatory in their use or are them some pointers on how to do it?
Thanks for any info,
In the garage, you say you will use a 16A RCD. This doesn't make sense. An
RCD has only earth leakage protection, but no overcurrent or short circuit.
I would use a B20A/0.03 RCBO for this purpose. This protects against all
Earthing is something that needs to be considered. If you decide to export
your house earth, you'll need to run main equipotential bonding to the
garage if it has any structural metalwork or metallic services. This could
be very difficult to achieve. It is much easier if there is no such services
The alternative is to install a TT system in the garage. This would consist
of an earth rod and a consumer unit with a 100mA Type S RCD incomer, a B16A
MCB for the freezer, a B6A MCB for lighting and the B20A/0.03 RCBO for the
general power. The RCBO is guaranteed to discriminate with the 100mA Type S
for earth leakage on the general power circuit. Although there are a number
of points of failure that could take out the freezer, the most likely is
eliminated (earth leakage on the socket circuit). It doesn't take much work
(or equipment) to install, although the earth rod would need to be tested,
and you would need an extra residual current device (which might cost a
Run PVC T+E in the house. Only go into armoured cable where you go through
the external wall. You should find instructions for installing the glands in
the packaging. Otherwise, a bit of googling (and a hacksaw) may help.
Lazy typing on my part! I'll either fit an RCBO or a cheap split CU
depending on which is cheaper..
There are no services in the garage fortunately so I assume it is
permissible to use the sheath of the cable as the earth in this
I'll continue googling then :) Having never worked with the stuff
before I want to make sure I get it right... Of course it may be
easier/cheaper to run 4mm T&E all the way, protected by conduit on the
Thanks for the reply,
Cheap split may be marginally cheaper, but RCBOs look more better! (and take
1 or 2 less ways in the consumer unit!).
And no structural metalwork? However, if you don't go TT, you really do need
to test the earth loop impedence properly using an earth loop impedence
tester (costs lots to buy). I'd be tempted to go RCBO on the other circuits
too, to be sure. Belt and braces.
I wouldn't use T&E for this. Definitely use SWA.
You can hire them. I hired one a couple of years ago over
a weekend, and there were several of us at work who used
it over that period (I think it was about 6 houses checked)
and shared the cost. It would be expensive to hire it to
check just one house.
A quick tip when connecting up the glands is that there is a small brass
ring as part of the connection. This ring is tapered and will only go on one
way - I spent 2 bloody hours trying to get the bastard thing to do up before
someone pointed this out to me :)
Other than that I found the job pretty straight forward with lots of advice
to be found on this group
Remove BRAIN before replying
The gland assemblies, which are normally brass, usually come with an
earth tag which goes onto the barrel and is held in place with the
nut. An earth wire is attached to that and run to an appropriate
To email, substitute .nospam with .gl
You may find it doesn't work so well there. Most freezers are designed to
work in the ambient temperature of the average kitchen.
For my garage, I ran T&E through conduit into to an external IP68 junction
box and took the armoured cable from there. The box does not need to be
metal. The terminations come with an earthing tag, so just connect that to
earth at one end of the cable.
The last ones I bought came with instructions, but I've always found them
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