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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