RE: Outside stuff and RCD

[Nigel Orr <Nigel.Orr@xxxxxxx>]

At 10:16 11/05/00 +0100, you wrote:
>I did consider this; but not knowing the technicalities of the X10
module, I
>am unsure :
>
>1/ If any short or leakage would pass-through the X10 module to the RCD
>correctly to allow it to trip,

The RCD should only trip when there is a difference between the current in
the live wire and the current in the neutral wire.  That should only happen
when the current is flowing through the earth wire, or through an
unfortunate person or animal to earth.

It's OK (IME) to use an RCD with speed-controlled drills etc which are
fairly unfriendly loads, so it shouldn't be a problem.  It's possible that
an RCD might false-trigger, but IME that only happens when you switch it on
with a biggish load attached and switched on (eg vacuum cleaner, power
tool).  It's easy to check it, and shouldn't do any harm at all to the
breaker.

>2/ That I would not fry the X10 module in the event of a short.

It's no more likely than damaging an X10 module inside- RCDs are really
just people-protectors, and should, if anything, help an X-10 module
plugged into them.  If you're concerned about it, I'd be happy to try an
appliance module in an RCD tonight to see if it works and if the RCD still
trips with the test button.

It won't make any difference whether the RCD is before or after the module
in that case anyway, once it stops the current flowing, it stops both
before and after the RCD.

Only potential problem would be if  X-10 modules lead to reduced RCD
sensitivity- and I can't see any way that could happen

> >_Don't_ just 'not use an RCD', water/outside/electricity is too
risky a
> >combination really... unless it's a low voltage pump and the
transformer is
>inside.
>
>This is interesting; I was actually putting two devices in; (mains
voltage)
>pump, and low voltage lights (with power supply in the house). Do I not
need
>the RCD for the lights then?

Not if they are marked SELV (safe extra low voltage).  The instructions
that come with them should advise if you need an RCD, but there's no reason
_not_ to fit an RCD, except initial purchase cost, and the possibility of
problems if it triggers falsely.  The first might be an issue, the second
probably isn't (unless the lights go out and you fall in the water
feature).  If you don't mind them both being on the same RCD, just leave it
like that.  It is good practice to have any external equipment which might
come into contact with people to be RCD-protected (in other words,
everything but security lights), if only because you might replace them
with mains-powered lights at a later date.

Nigel


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