From owner-freebsd-questions@FreeBSD.ORG Thu Oct 17 13:44:26 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 68E0025E for ; Thu, 17 Oct 2013 13:44:26 +0000 (UTC) (envelope-from frank2@fjl.co.uk) Received: from bs1.fjl.org.uk (bs1.fjl.org.uk [84.45.41.196]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id D60BE20DC for ; Thu, 17 Oct 2013 13:44:25 +0000 (UTC) Received: from [192.168.1.35] (host86-163-34-162.range86-163.btcentralplus.com [86.163.34.162]) (authenticated bits=0) by bs1.fjl.org.uk (8.14.4/8.14.4) with ESMTP id r9HDiN3o083811 (version=TLSv1/SSLv3 cipher=DHE-DSS-CAMELLIA256-SHA bits=256 verify=NO) for ; Thu, 17 Oct 2013 14:44:23 +0100 (BST) (envelope-from frank2@fjl.co.uk) Message-ID: <525FE9B7.6080307@fjl.co.uk> Date: Thu, 17 Oct 2013 14:44:23 +0100 From: Frank Leonhardt User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: freebsd-questions@freebsd.org Subject: Re: OT: UPS buying suggestion References: <525F0138.1020304@fjl.co.uk> <20131017093820.6a8428de@X220.ovitrap.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> In-Reply-To: <1382015420.5852.97.camel@archlinux> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Content-Filtered-By: Mailman/MimeDel 2.1.14 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 17 Oct 2013 13:44:26 -0000 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!