On 24/04/2019 19:40, ARW wrote:
On 24/04/2019 19:11, wrote:
I've had to connect an external pump controller (for a well) to a
house circuit that's on a 30mA RCD. I'd prefer to have some
discrimination but don't want a delayed RCD on the house circuit, any
ideas?
I wondered whether there is a fast-acting 10mA RCD available that I
could use for the controller but I suspect the 30mA RCD would probably
trip as well. If not, and nobody can suggest another solution, I'll
leave it as it is, or (possibly) use an isolating transformer.

I agree both or either would trip. You are probably not allowed a time
delay RCD on the house.

New dedicated circuit with it's own RCD?

A new circuit would be the "correct" answer but it's not really viable -
a large house with awkward runs and the need to drop down a plastered
wall. Having just looked at the price of 1kVA isolating transformers I
don't think they will be an option either.