wrote:
You also need to decide where you will site the RCD. In this
circumstance at the head end of the supply would probably be acceptable.
Depending on the earthing system in user you may or may not have a choice.

Thanks for you comments,

I was going to site the RCD where I change from TC&E to the Armoured
Cable is this not suitable. Do I need to run a separate earth cable
will the one in the TC&E nor suffice?

You can have the RCD here if you want so long as you have a TN-S or
TN-C-S earthing system in use at the head end. With a TT system at the
head you would need some form of RCD protection at the head end to
protect the T&E from the consumer unit to the point of changeover to SWA.

With RCD protection on the SWA there is no real worry about the size of
the earth. This only becomes an issue when you have a long run that is
not protected by a RCD at the head end, and you need to make sure that
disconnection times can be met in the event of a fault to earth on the
SWA. The RCD makes this issue go away.

--
Cheers,

John.

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