[chbot] OT: Low profile RCB

[Charles Manning]

On Mon, Jul 14, 2014 at 10:36 AM, Volker Kuhlmann
<list0570 at paradise.net.nz> wrote:
> On Sun 13 Jul 2014 23:11:03 NZST +1200, Marshland Engineering wrote:
>
>> Coming from South Africa - every (we legal) house had an RCD in line
>> the incoming mains. Ie every circuit was protected. I've did this in
>> our house we built 14 years ago an never had a problem. Would do the
>> same again.
>
> Not legal in New Zealand. It's also a really bad idea to have a single
> RCD for your whole house!

Why?

Sure it is better to have multiple RCDs and reduced "fan-out", but
surely having one RCD is supremely better than having none.

>The limit here may be 3 breakers per RCD now.
> I bet it's partially to stop unscrupulous tradespeople from increasing
> profits by creating substandard installations (a single RCD for a house
> is substandard as far as I am concerned, no matter the law).
>
>> If fridges and freezers start to trip it - get rid of them and get
>> new.
>
> Yes. Because in a house meeting current requirements they must have an
> RCD and therefore would no longer work.
>
> But that system fails with heaters, because heating elements have a
> natural earth leakage when hot. I last noticed this when I tried to get
> a heater an RCD, but each of the 1.5kW elements alone would trip the
> 30mA RCD within 45s when cold. All elements were out of the box and
> unused. That's why large heaters with fixed installation (kitchen
> stoves, hot water elements, etc) don't need an RCD. It wouldn't work
> anyway. All of these appliances must still be earthed, shouldn't be
> opened and have fixed wiring, so an RCD would give little extra
> protection anyway.

Seems to work in South Africa when I lived there, but maybe the laws
of physics were different under apartheid.

I clearly remember having hot water (though we called hot water
cylinders "geysers"), bar heaters, refrigeration and washing machines.

As an experimental kid I also "tested" the RCD on occasions and it worked.