Sparks wrote:

Okay, the origanal question was why shouldt I connect the house earth to the
garage TT earthing arangement - why must they be kept seperate?
(The cable run up to the garage is about 50m in 4mm SWA)

Well if you connected them together it would no longer be TT, but nobody
should have said that isn't allowed. It depends what you're intending
to do in the shed and whether the equipotential zone concept can be
properly applied there. If you search Google groups for "shed
electrics" you'll find plenty of previous threads to muse over.

NB 2. Reg. 551-02-03 requires automatic load shedding arrangements if the
generator is not rated to supply the whole installation.

So it has to be impossible to switch on too much?
or can there just be some instructions to turn off some MCB's?

What it says is "Means shall be provided to automatically disconnect
such parts of the installation as may be necessary if the capacity of
the generating set is exceeded."

--
Andy