In article ,
The Natural Philosopher writes:

In reality you need a 20A plus triac to control e.g. a 2A load So the

This will also increase the minimum load the dimmer can dim
correctly. However, it won't increase the maximum load, which
is governed by heat dissipation, not size of triac (you will
find all dimmers are fitted with triacs which can handle much
more current than the rating written on the dimmer).

MCB trip goes before the triac, not the oher way about.

An MCB takes half a mains cycle to trip. It depends what the
prospective short circuit current is at that point in the
circuit, and if the triac can take that for half a mains
cycle. A larger one is more likely to, but it's not a dead
cert. For an (expensive) X10 DIN rail mounting dimmer, I have
put a (cheap) 3A (B3) MCB next to it. The dimmer has had no
problems, but then I don't know if it would have without the
MCB. The MCB trips in preference to the dimmers 3A fuse.
The MCB protects only the light on that dimmer -- you don't
want a B3 MCB protecting a whole lighting circuit.

--
Andrew Gabriel