Assuming the RCD is working correctly it would trip between 10 and 20
milliseconds while carrying 30mA (depending on type). To quick for you to
feel it I would think but as they say 'Don't try this at home folks'.



Thanks. Quite a useful thing to have then. Why don't they build one into
the
electricity meter and then all homes would automatically have one? An even
better design would be to have a small light on the meter that came on
when
the RCD trips, then you would be able to see to turn it back on again.

This isn't done because a whole house RCD is not a good idea...

Say you were working in your workshop at night and you tripped it, what
would happen?
(All the lights would go out too!)

Sparks...