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Date:      Thu, 17 Oct 2013 16:16:53 +0200
From:      Ralf Mardorf <ralf.mardorf@alice-dsl.net>
To:        freebsd-questions@freebsd.org
Subject:   Re: OT: UPS buying suggestion
Message-ID:  <1382019413.5852.129.camel@archlinux>
In-Reply-To: <525FE9B7.6080307@fjl.co.uk>
References:  <CACo--msUpY-6r7MkuEvrPDpSVdFZyBotSA-eS7aLGMFDeq_vDQ@mail.gmail.com> <alpine.BSF.2.00.1310150911510.97788@wonkity.com> <CACo--mvUfcAy=0hyun21DZwSmdd=SmP7EeU-FVxJyiT_h4Rxkg@mail.gmail.com> <525F0138.1020304@fjl.co.uk> <20131017093820.6a8428de@X220.ovitrap.com> <alpine.BSF.2.00.1310162309200.14022@wonkity.com> <1381988697.5852.16.camel@archlinux> <20131017142910.61325830@X220.ovitrap.com> <1381992680.5852.45.camel@archlinux> <525FD4C8.1090600@fjl.co.uk> <1382015420.5852.97.camel@archlinux> <525FE9B7.6080307@fjl.co.uk>

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On Thu, 2013-10-17 at 14:44 +0100, Frank Leonhardt wrote:
> On 17/10/2013 14:10, 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 - 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.
> >
> >
> 
> Bemessungsdifferenzströme = residual current rating (i.e. trip
> current). 1A! No good to stop a human being zapped, but might prevent
> a fire in the circuit. It'd be completely illegal in England,
> including in the workplace (I THINK). Certainly no more than 30mA for
> shock protection (or 10mA for low-voltage application like 110V. I
> know it's possible to fit 300mA where only fire prevention is needed;
> I've never seen anything higher than that, but I'm not an electrician.
> 
> As you say, your friend was lucky!

I don't know for what usage 1A is legal in Germany, it's not my job or
hobby. I didn't read the complete wiki and perhaps the wiki doesn't
explain it. The friend and I also only know RCCBs with a residual
current rating of 0.0xA, excepted of the exotic one at this farm.
However, I've seen mains sockets installed, connected by thin speaker
cables, diagonal mounted behind a styrofoam wallpaper in a girlfriends
flat.

This is forbidden in Germany. 1. Ground is needed. 2. Reasonable cables
are needed. 3. An empty conduit for the cable is needed. 4. Diagonal is
a no-go, there are sane rules how to install a cable.

Btw. even for the sockets we have a _law_ in Germany, that ground has to
be longer than the other cables and similar "trifles", but averaged
hobby experts aren't aware about it.

I guess German standards/rules/laws for all kinds of engineering are
still the hardest on this planet, but in reality they are much too often
violated.




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