On 02/08/2019 18:19, Chris Green wrote:
I sort of understand how cables going into round holes in a CU can have
the gaps filled so that the non-inflammability requirement is
fulfilled. ...or in the case of round cables they will fit snugly in
the right sized gland.

However I really can't see how one is meant to use the relatively
large rectangular 'mini trunking' holes while retaining fire
protection. The holes in my new CU are something like 5cm x 3cm, is
one meant to run cables in trunking that size up to the holes with the
trunking butted up against the CU case? Or is the trunking meant to
run along the CU with holes in the trunking to route cables into the
CU?

Either way, where does the trunking stop? Does one have to gunge up
the other end where the cables come out of the trunking with
intumescent gunge? Since my CU is flush mounting the trunking isn't
going anywhere in particular and there's not another end where the
cables disappear into a wall or something.

Mini-trunking is PVC which is somewhat fire resistant.