In article ,
"Robert" writes:
I have 2 differential switches (ELCB's) in my electrical system.
One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp switch,
my new 1600 Watt electric grass verticutter causes the switch to trip at the
slightest (physical) resistance.
When plugged into a circuit using the 0.30 Amp switch, after a short test, I
have had no problems.

This does not sound normal to me; should I be worried?
The fuse does not go, so does this mean there is a short to earth somewhere?

Sounds like the verticutter(?) has an earth fault.
(Never heard of one before, but I would have expected it to
be double insulated, so must be leak to the ground under it).
There are other possibilities such as incorrect wiring of the
20A circuit. Try a different high current load on it like a
kettle or 2kW heater, and see if the same happens. Since we
are suspecting there could be a wiring fault, it would be a
good precaution during such a test to assume the earthing
could be faulty, so avoid touching the test appliance(s)
when they are switched on.

--
Andrew Gabriel