Text 9987, 107 rader
Skriven 2010-08-17 15:39:54 av Michiel van der Vlist (2:280/5555)
     Kommentar till en text av Robert Bashe (2:2448/44)
Ärende: Just Curious
====================
Hello Robert,

On Monday August 16 2010 08:37, you wrote to me:

 MV>> Both are allowed, although in new installations yoy will mostly
 MV>> find circuit breakers. I prefer the one that we cal "smeltzekering".

 RB> The Germans call that a "Schmelzsicherung" (melting fuse).

Figures...

 MV>> The one time fuse where a wire melts when it is overloaded. Unless
 MV>> you make shorts very often they are cheaper. But that is not the
 MV>> main reason for my preference. I judge them to be more reliable. A
 MV>> circuit breaker (Stotz) is a fairly complicated electromechanical
 MV>> device. It can fail, especially after having been activated many
 MV>> times. The old fuse with the melting wire is almost infallible.

 RB> As for the economics, you're of course right (although I don't know if
 RB> fuses are allowed on in-house 16A circuits in the newest building
 RB> codes in Germany, the regulations are pretty complex and not always
 RB> understandable for a layperson).

Same here, plus that they often change. What is ok today may not nbe ok bnext
year and vice versa. On the bright side, is that here regulations are not
*binding*. They are guidelines. The basic rule is that the installation must be
safe. Following the regulations makes it safe - or so they say - but if one
wishes to do it in another way that gives the same level of safety, that is
allowed in priciple. Of course one may have a hard time convincing the
insurance company if something goes wrong...

 RB> However, if you've ever had a fuse blow on a Sunday night, when you
 RB> can't buy a replacement and just by chance have no spares at hand,

That has never happened to me and will never happen. I always have plenty of
spares. If I blow 20 fuses in a row on a Sunday night, it is time fro more
drastic measures then just blindly replacing fuses.

 RB> you start to appreciate the breakers more. And of course the breakers
 RB> have the advantage that people can't abuse them like they sometimes do
 RB> fuses - wrapping a burnt-out fuse with aluminum foil, or shorting the
 RB> socket with a (US) penny are famous ways people have used to restore
 RB> power - and often tu burn down their house.

It is hard to make things idiot proof.

But what is stopping an idiot from replacing a 16A breaker with a 50A one if it
keeps triggering?

Another reason I prefer the classic fused is that they do not so easly trip
when switching on heavy equipment with inductive loads. Welding transformers
are notorious for tripping circuit breakers. I have a welding transformer...

 RB>>> - the ones from the power lines in the street to the internal
 RB>>> lines in the house - and they're higher capacity)

 MV>> Some power companies use circuit breakers for those too in new
 MV>> installations. (resetteable by the customer) Others take my POV...
 MV>> (In a sealed box, not replaceable by the customer).

 RB> Our main line fuses can be replaced by the customer -

How does the power company stop people from stealing electricity if they can
simple tap in before the meter by removing the main fuses and plugging in
something else?

 RB>  replacements in the building supply markets - but as I say, we've
 RB> never had the need to do this. Only the breakers have ever tripped
 RB> here.

I never had a main fuse blown either. But I do have some 35A fuses for a
replacement. Yes, I am not supposed to do that myself, but if it happens on a
Sunday night, I will break the seal and replace the fuse myself. Then next
morning I will call the power company and ask them to replace the seal. They do
not like that, but if they can not prove fraud, there is not much they can do
about it.

 RB> We also have what they call FI switches here, which trip and interrupt
 RB> the power when a certain small amperage (I believe 50-100 mA) drains
 RB> to ground, as when a grounded person touches a live line or the
 RB> insulation in an appliance is no longer completely adequate (but still
 RB> doesn't short out).

Those are a circuit breaker and an earth differential switch in one package.
They trip at 16 A overload or 30 mA differential. Here they are called
"alamat".

I prefer the circuit breaker and the earth differential switch to not be
combined in one package. An "alamat" compromises the "three faults rule". Some
parts are shared by the 16A and 30mA function and so one fault could make both
the overload and earth leakage function fail.

Also it is an even more complicated electromagnetical device, so more can fail.

 RB> They are required for all new buildings (and were required in 1985,
 RB> when we remodeled our house, so this is nothing new). The original
 RB> purpose was to keep cows who licked electric lines from being
 RB> electrocuted on farms, but they are now ubiquitous in private homes as
 RB> well, the purpose being to prevent accidental electrocution.

As I explained in my message to Scott, the earth differential switch replaced
the "two faults rule" by the "three faults rule".

Cheers, Michiel

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