[chbot] OT: Low profile RCB architecturally

[Mike Barnes]

Hi Charles 

I have to agree with Volker, all is good in your house until you have a
fault. In your case nothing in your house will work and then you have to
isolate 40 sub circuits to find that fault. 
This will normally happen in bad weather when it's cold and wet.
Under the new regulations having more RCDs in the switchboard is better,
when there is an issue only 3 outlets and some lights are affected.
The oven, hobs and heat-pump are not on an RCD which is normal in modern NZ
wiring.  

I have seen this very issue in my in-laws house. Their nice architecturally
designed outdoor lights seem to fill up with water, causing a fault to
earth.

At least their fridge /freezer and heaters still work until they drain the
offending light(s).....................again! 

Regards
Mike


-----Original Message-----
From: chchrobotics-bounces at lists.linuxnut.co.nz
[mailto:chchrobotics-bounces at lists.linuxnut.co.nz] On Behalf Of Charles
Manning
Sent: Tuesday, 15 July 2014 11:01 a.m.
To: Christchurch Robotics
Subject: Re: [chbot] OT: Low profile RCB

Volker

Sorry if you thought the questions I posed were trolling you or anything
like that. I was genuinely interested in why you would think a single RCD is
a defective design.

I do understand that killing all the electricity when just one appliance is
faulty is overkill, but in reality RCD faults should hardly ever - perhaps
never - be triggered so the difference between a good design and overkill is
small. You're far more likely to need to keep a flashlight/torch on hand for
the normal power loss events that hit us a few times a year.

Still it is probably wrong to dismiss as "stupid" a single RCD design that
is used successfully in tens of millions of houses in South Africa over the
last 50 years.

I never saw a radiant heater or a water heater trip an RCD in South Africa,
but then I never tried using a 6kW heater. I was envisaging an appliance
style heater (~2kW maybe).

Some years back I was talking to an NZ electrician and he said they didn't
wire laundries through RCDs because there's so often leakage in wet areas.
That stunned me. Surely if there is chance of leakage, that is exactly where
you want an RCD!




On Tue, Jul 15, 2014 at 10:03 AM, Volker Kuhlmann <list0570 at paradise.net.nz>
wrote:
> On Tue 15 Jul 2014 08:54:24 NZST +1200, Marshland Engineering wrote:
>
>> 30 ma is 30 ma regardless of how many breakers you have. We have one 
>> 3 phase RCD of 30 ma one feeding about 40 CB. We have a 'big' house 
>> many flouresecnt tubes, 1 fridge, 3 freezers, 1 large mill, 2 large
lathes, 3 hot water cylinders, 2 heat pumps, dozens of computers, one 4 kw
oil heater, washing machine, tumble drier, and still, I've never had to find
and reset the RCD in the dark (or even the light for that matter).
>
> And all those loads were connected downstream of theRCD? Are you sure?
>
>> >Seems to work in South Africa when I lived there, but maybe the laws 
>> >of physics were different under apartheid.
>>
>> Oh yes. Made me laugh.
>
> Keep laughing, I don't care. You two smartalecs are welcome to come 
> over and do your own measurements on the 6kW heater I have here. Your 
> suggestion of replacing a brand-new heater here in New Zealand just 
> because it doesn't fit your South African wiring made *me* laugh...
>
> Volker
>
> --
> Volker Kuhlmann
> http://volker.top.geek.nz/      Please do not CC list postings to me.
>
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