Tim Downie wrote:

A friend of mine has a pond with pump & lights wired into a fused spur from
the house ring-main (which is RCD protected). After some recent heavy rain
(which probably managed to penetrate a supposedly "water-tight" outside
junction-box, the RCD tripped, which wouldn't have been a problem if he
hadn't been away on holiday at the time and the fact that the freezer was on
same circuit.

Yup, you don't want to start from there! ;-)

I wondered about changing the existing fused spur for another RCD (like this
one
http://www.screwfix.com/app/sfd/cat/...00509&id=83049)
but I see that it has the same 30mA trip current as the existing one in the
main fusebox

Would I be right in thinking that this wouldn't necessarily stop the main
fusebox RCD tripping?

You would.

Would one with a lower (20mA say) trip current work (and do such things
exist)?

alas no.

Read the sections on discrimination, mitigating the effects of nuisance
trips, and system design using RCDs he

http://wiki.diyfaq.org.uk/index.php?title=RCD

to get a feel for the available options.

There is also a fair bit or relevant info in this one:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside



--
Cheers,

John.

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