In an earlier contribution to this discussion,
Christian McArdle wrote:


Don't be so sure. You want the house end to blow as slowly as
possible to get maximum possible discrimination with the garage CU. I
would consider a Type C MCB, or even an HRC fuse. If 40A is allowed
as well, then use that, too. I haven't done the calculations so can't
tell you what you will get away with. This way, any fault is more
likely to be picked up at the local MCB in the garage.


Is there an idiot's guide somewhere, defining the calculations which I need
to do?

As mentioned in my post in answer to Andy Wade, I had previously been
advised (back in June) to use a Type B MCB, and to go for 32A rather than
40A in the light of my rather weedy 2.5mm^2 earth wire - so I'm getting a
bit confused!

* Use 3-core SWA cable, and use one core (6 mm^2) as the earth - and
join it onto the end of the T&E's 2.5mm^2 protective earth conductor
- thus exporting the earth from the domestic CU

I'd just do this given you are only 1.1m from the house. This is only
possible if the garage has no main equipotential bonding
requirements, or the main equipotential bonding can actually be
achieved.
It's 1.1 metres as the crow flies - but about 6 metres of SWA down the wall,
across the gap, and into the garage. Does this make any difference - or are
we only looking at the likely difference in earth potential between 2
adjacent buildings?
There will be no 'services' (water, gas, etc) in the garage, and no
equipotential bonding is required AIUI.

--
Cheers,
Roger
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