Dave Plowman (News) wrote:

You miss the point. You'd have to bridge line and neutral within the trip
time of the RCD. That's what I was querying.

Not if it's the N you touch first - there'd be naff-all current passing
through you given the negligible potential between N and local earth,
together with the much higher resistance which you present as a path to
earth/transformer-return as compared to the copper path it's got. Then
when you make contact with L (other side of the finger - possible
finger-cooking but little likelihood of death; other hand - definite
risk of fatality, hence the habit inculcated into generations of
sparkies of working with one hand at a time) you become an attractive
path for L-to-N current; and by far the greater part of the flow through
you will be on the L-to-N path, which doesn't do anything to trip the
RCD, rather than the L-to-E-via-shoes/clothes/whatever which the RCD is
sensitive to.

I'm not, of course, saying they are perfect. But perhaps better than
nothing?

Definitely better than nothing, but not a cure-all, and a possible
source of a "risk compensation" effect - "oh, it's OK to work live on
the electrics, I have a whole-house RCD"...

Stefek