In an earlier contribution to this discussion,
John Rumm wrote:


There is already a live cross connection between the output of the
main switch and the input of the RCD. I assume that the part of the
busbar serving the non-RCD-protected ways needs to connect into the
same output from the main switch?

Yup, check the wiring carefully though, making sure it is correct and
tight! (I had a contactum CU where the wiring as supplied was
seriously wrong!)

Yes, the way it's pre-wired corresponds with the leaflet which came with it.

[Next bit I am doing this from memory - so if it does not make sense
when you look at your one, ignore me!]

Assuming you are going with the main switch on the right, and the RCD
in the centre, then the phase and neutral from your SWA run into the
top terminals of the main switch (phase on left). The bottom right of
the main switch ought to have a neutral connection to the non RCD
neutral busbar - there may also be a connection to the top neutral on
the RCD (or that will more likely come from a wire on the end of the
first nutral bus bar). The phase (bottom left) of the main switch
ought to connect to the main phase busbar AND the flylead to the (top
left) phase input of the RCD. The phase output of the RCD (bottom
left) should then feed the other bit of phase busbar, while the
bottom right of the RCD should have a lead to the second neutral
busbar.
Any of that seem plausable?

Yes, that's exactly right.

As supplied, neither the main switch nor the RCD will turn on. Is
this because they need a mains supply before they will operate, or
are they duff?

It is normal for a RCD, but not a switch (assuming it is just a bog
standard two module wide switch). The Switch should snap from one side
to the other, with a bias toward "off".

On trying again, they *do* in fact turn on. It's just that they take more
force than I was expecting - and I didn't want to break anything!


Finally, bearing in mind that this is an insulated rather than
metalclad CU, what's the best way of terminating the incoming 6mm
SWA cable? There's no obvious place on the casing to fit an SWA
gland. Do I need a junction box next to the CU for this purpose?

Personally I would drill a suitable sized hole to take the SWA gland
to make it neat and tidy. Then use a ring terminal on the gland to
pick up the earth from the shield, and take that to the earth busbar
(along with the third core if you have one!).


There isn't really anywhere suitable in the body of the thing to drill
holes - apart from some knockouts in the back. But I'm not planning in
coming straight through the wall into the back for several reasons. My
current thoughts are that I will drill a 20mm hole in a piece of aluminium
angle to take the gland, and screw the angle to the wall near the top RH
corner of the CU, and just take the conductors in through a cutout in the
cover. If I fix the angle and gland *first*, and then position the CU next
to it, there won't be any exposed cables.

Thanks again for your help and support.
--
Cheers,
Roger
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