Text 9992, 130 rader
Skriven 2010-08-18 11:18:13 av Michiel van der Vlist (2:280/5555)
     Kommentar till en text av Robert Bashe (2:2448/44)
Ärende: Just Curious
====================
Hello Robert,

On Wednesday August 18 2010 08:03, you wrote to me:

 MV>> Sure they do, no problem. These dircuit breakers are pretty
 MV>> standarad and available up to 63A in the same housing.

 MV>> http://tinyurl.com/27ywxzu

 RB> Our circuit breakers look different - about half the thicknesss of the
 RB> ones you show.

The ones I showed you are the classic full width, dual pole variety. They
interrupt both the live and the neutral, but they sense only the live wire.
They are 36 mm wide.

There is a single pole half width variety (18 mm wide) that only interrupts the
live. These are allowed in some countries.

A newer variety is two pole, half width.

So you either have the single pole, or the newer half width, dual pole variety.

There are also 3 and 4 pole varieties. Most are double width (72 mm).

I assure you that all of these are available up to 63 A.

 MV>> And if you can not find one... what is stopping an idiot from
 MV>> bridging it with a piece of wire?

 RB> ;-) Or a penny... OK, if you are absolutely determined to do
 RB> something, there's not much to prevent you doing it. I was assuming
 RB> some modicum of responsibility.

A responsible person would not "rewire" a classic fuse either.

 RB>>> And of couse, that would be more work than shorting a fuse. Have
 RB>>> to think of the laziness of people ;-)

 MV>> Not if they are of the new "just insert, no screws type"...

 RB> Maybe. The ones I have are attached by screws and you have to remove a
 RB> piece of metal to get at them. It's not a huge job, but it is work.

It all depends how deperate and determined the idiot is. Some idots can be
prettty determined. ;-)

 RB>>> The fuses are _after_ the meter, not before.

 MV>> Ah, I see.

 RB>>> No way you can get at the lines going into the meter unless you
 RB>>> actually work with the live wires - and something like that would
 RB>>> be evident the next time the meter is read or the electricity
 RB>>> company wanted to check anything.

 MV>> I would not be too sure of that. Things like that HAVE been done
 MV>> you know.

 RB> I know. What is possible will be done. But it's not something somebody
 RB> with two left hands does in 15 minutes - and of course, such work is
 RB> very dangerous.

I have worked with live circuits several times in my life. I am not looking for
it, but I can do it if I must.

And of course professionals do it al the time. How do you think they connect a
new house? They do not blank out the whole street for that. No, they make a hot
tap into the main cable in the street.

 MV>> Here the main fuses are befort the meter.

 RB> None afterward except for the breakers for the various internal
 RB> circuits in the house?

No, what would be the point?

The main fuse is 35A. The fuses for the individual circuits are 16A.

A second main fuse of 35A is pointless. In case of an overload it would be a
matter of change which one blows. The one before or the one after the meter.

Cascaded fuses must always go in a descending with a minimum of a factor 1.5
between steps in order to maintain selectivity. So the intermediate fuse would
have to be 25A.

But that would limit the load capacity. I could not have the full 16 A on two
circuits on the same intermediate fuse.

 RB> Your description of the electric setup is interesting, but for me
 RB> pretty confusing. I've never gone into the subject seriously, and a
 RB> lot of this is the "great unknown" for me.

I have studied it....

 RB>>> There are circuit breakers for the various circuits in the house,
 RB>>> and a line of FI switches at the top of the electric cabinet for
 RB>>> the various circuits in the house.

 MV>> So each circuit has its own FI switch?

 RB> To be honest, I don't know. However, I think that several circuits are
 RB> on one FI switch, as there are more circuit breakers than FI switches.

You said they were above the circuit interrupters. If there are less than the
number of circuits they must be electrically before the circuit breakers. Just
like they do here...

 RB>>> I might add that 30 mA seems a little low to me. I think we have
 RB>>> 50 mA here,

 MV>> Doubt it. 30 mA is a EU standard. Heve a close look at the thing,
 MV>> the rating wil be on it. In small print....

 RB> Have to check that later.

 MV>> There exists a 10 mA variety. Maybe you had one of those. One can
 MV>> indeed overdo things.

 RB> You may be right. I'll check and get back to you.

Actually I am stiil looking for a 10 mA FI switch. i want it in the caravan, so
that in case of a ground fault, I only trip my own FI switch and not the one in
the connection box that is shared with others campers.


Cheers, Michiel

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