"sean mckinney" wrote in message
...

With regard to fitting an RCD to the supply to a pond,
I would fit the RCD in the house as has been suggested so that it
protects everything outside the house.

HOWEVER,

I believe the standard RCD's available in the UK as rated at 30 and 50
mA trips, I assume you are UK based since you use the term RCD and the
email address. After seeing, and being involved in, some interesting
debates on electrical safety on some of the american boards, where
earthing of the pond water directly to the ground and unearthed devices
are not uncommon, I performed a series of experiments to check the
effectivness of a 30mA RCD

http://tinyurl.com/7ez7k

http://tinyurl.com/96twm

You may have to register with either or both of those boards to see the
threads, sorry.

DO NOT attempt the experiment yourself, I had a reasonable idea of what
I was doing

The conclusion of the experiment is, that if a submerged 'break' in the
insulation of the live etc occurs some distance away from a good earth a
30mA RCD may not 'see' enough leakage current to trip and thus the water
will still be live. BTW my 30 mA RCD was and is working perfectly well,
in fact I measured the current required to trip it and that current
was, from memory, in the low to mid 20 mA range, ie below 30mA.
An american, Johns, repeated the experiment with a US spec 5mA tripping
RCD/GFI and that did trip, see the 2nd of the links above. I would
therefore suggest that you try to get a 5mA trip RCD, unfortunately I
dont know if they are available.


--
sean mckinney
Thanks for everyones replies. I am in the UK, if I understood Sean correctly
I think you are saying if I cannot get hold of a 5mA RCD, it would be better
to have an RCD with an earth as near as possible in cable length terms to
the pond as well as an RCD inside which would trip the circuit if a spade
went through the outdoor cable?

Thanks,

Will