OT: UPS buying suggestion

Ralf Mardorf ralf.mardorf at alice-dsl.net
Thu Oct 17 13:15:46 UTC 2013

On Thu, 2013-10-17 at 15:10 +0200, Ralf Mardorf wrote:
> On Thu, 2013-10-17 at 13:15 +0100, Frank Leonhardt wrote:
> > On 17/10/2013 07:51, Ralf Mardorf wrote:
> > > On Thu, 2013-10-17 at 14:29 +0800, Erich Dollansky wrote:
> > >> Industry is much worse. Their machines made early computers fail when
> > >> the bigger machines started work.
> > > I worked for an audio company. The audio workshops were rented rooms on
> > > a farm, and the boss missed to check the values of the RCCB, which
> > > nearly killed a friend. Bigger machines are a PITA ;). The RCCB had a
> > > value that high, that it was dangerous to life for an audio workshop. A
> > > big machine not only pollutes the mains, if you turn it on, it also will
> > > "eat" the complete power and lots of it going in, doesn't come out. A
> > > "normal" RCCB would turn off immediately.
> > >
> > >
> > Most RCCB (aka ELCB, RCD) work (hereabouts anyway) work with 
> > counter-wound coils on the input and output of the supply such that he 
> > magnetic field is neutral if the current is the same. If it goes out of 
> > balance, it trips the switch. Normally 30mA difference is the rule. They 
> > don't have a value, as such. I heard that only 10mA is needed to 
> > interrupt your heart, but I've also heard 100mA. They're all potentially 
> > dangerous. It depends on the route taken by the current passes through 
> > your body

Correct, I've got professional literature about this issue, but I'm to
lazy top take a look now. Don't trust a RCCB!

>  - you'd have to try quite hard to get even 10mA in the wrong 
> > place, but I guess you could do it with rubber shoes and grasping the 
> > mains one your one hand and an earth spike with the other. I was taught 
> > to keep my left hand in my pocket when poking around stuff that might be 
> > live, and do it quite subconsciously.
> The one at home, in Germany called FI, has got a value of 0.03A for my
> flat, the one at the farm had a value of 1A.
> "Handelsüblich sind Fehlerstromschutz-Schutzschalter in der Bauart A für
> Bemessungsdifferenzströme von IΔN=10 mA, 30 mA, 100 mA, 300 mA, 500 mA
> und 1 A." -
> https://de.wikipedia.org/wiki/Fehlerstromschutzschalter#Kennwerte
> The keyword is "Bemessungsdifferenzströme", sorry I can't translate it.
> 30mA is save, 1A will kill you, since it won't turn off the power if
> your body should become the resistor.
> As mentioned before, a workshop in addition must use an isolating
> transformer, by this galvanic isolation you can't get an electric shock
> if you only have contact to the phase and ground. You need to have
> contact to phase and neutral conductor to get a shock.

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