Volker: Thanks for the explanation. I am left with 2 questions:
1. You wrote "The new decision is not part of the upcoming safety standard for IT products, IEC 60950 3rd edition, which is likely to be available beginning of next year". What does that omission tell us? If the 3rd edition has been written by people aware of the OSM/EE decisions, who consciously did not include the decisions in the new edition, then do they mean that varistors to ground are acceptable and not subject to the "requirements" in the 2 decisions you quoted? 2. It isn't clear whether the recent decision allows a varistor approved to IEC 601051-1 without a spark gap and fuse or whether the new decision overrules the old decision in this respect. Thanks again for any clarification anyone can offer. Regards, Jim Eichner Statpower Technologies Corporation jeich...@statpower.com http://www.statpower.com Any opinions expressed are those of my invisible friend, who really exists. Honest. > -----Original Message----- > From: Volker Gasse [SMTP:ga...@de.ibm.com] > Sent: Tuesday, December 15, 1998 2:34 AM > To: emc-p...@majordomo.ieee.org > Subject: RE: Varistors to ground > > > The mentioned Cenelec decision is taken from the 'List of decisions > from > CENELEC Operational Staff Meeting for Electronic Equipment (OSM/EE)'. > Here representatives from EU Testhouses meet to discuss > interpretations of > clauses in safety > standards such as EN 60950 for IT products. These decisions are to be > followed > by all European > testhouses. However, those decisions should be > interpretations/clarifications > to the existing > standards, but not addition of new requirements. > > For EN 60950, Clause 1.5.1, Decision 98/2 states: > > 'A combination of a varistor in series with a spark gap (Gas-Tube) > [between the mains and the protective earth] > complying with Basic Insulation, and with a fuse will be accepted for > > a. Pluggable equipment Type B and permanently connected equipment: by > all > countries > b. Pluggable equipment Type A: by all countries except DK, UK and SE. > For pluggable equipment Type A two fuses are required.' > (To be sure that even by non-polarized plugs a fuse is provided) > > This interpretation is an extension to a decision which was already > issued in > 1/94: > > 'If a Varistor is separately approved according to Publications IEC > 601051-1 > and IEC 601051-2, it can be accepted without a protective device. If a > Varistor is not separately approved, a protective device against the > short-circuit is required. > Varistors tested according to CECC 42200 are considered as acceptable > in the > same way as tested to IEC 601051. > Varistors between the mains and the protective earth cannot be > accepted by the > following countries: > Pluggable equipment, type A: > Austria, Belgium, Denmark, Finland, Norway, Sweden, United Kingdom.' > The new decision is not part of the upcoming safety standard for > IT products, IEC 60950 3rd edition, which is likely to be available > beginning > of next year. > One of the reasons for requiring the spark gap in series with the > varistor is a > possible increase > in leakage current if the varistor has been exposed to several mains > transients. > > It should be noted, that IEC/EN 60950 does not require the use of > transient > suppressing > components. > > Concerning the > > mit freundlichen Gruessen/ best regards > Volker Gasse > > IBM Germany, Technical Relations/Product Safety, > Tel: +49 7031-16-6796, Fax: -6916, e-mail: ga...@de.ibm.com > Mail: 3114/7103-91, D-70548 Stuttgart, Germany > > ---------------------- Forwarded by Volker Gasse/Germany/IBM on > 15.12.98 11:20 > --------------------------- > > > owner-emc-p...@majordomo.ieee.org on 15.12.98 02:11:00 > Please respond to jeich...@statpower.com > To: j...@bighorn.dr.lucent.com > cc: emc-p...@majordomo.ieee.org > Subject: RE: Varistors to ground > > > John: Sorry I can't help, but I am interested in what replies you > get. > > > I also wonder what force the Decision carries. Is it a mandatory part > of the Low Voltage Directive? How does it relate to the LVD or to the > various EN's in force under the LVD? > > Thanks in advance for any light you can shed on these murky waters! > > Regards, > > Jim Eichner > Statpower Technologies Corporation > jeich...@statpower.com > http://www.statpower.com > Any opinions expressed are those of my invisible friend, who really > exists. Honest. > > > > > -----Original Message----- > > From: Boucher, John [SMTP:j...@bighorn.dr.lucent.com] > > Sent: Monday, December 14, 1998 9:07 AM > > To: 'emc-p...@ieee.org' > > Subject: Varistors to ground > > > > All: > > > > I have received a copy of a CENELEC Decision (dated 6/98) regarding > > the use > > of varistors between mains conductors and ground. This particular > > Decision > > is written in a rather unclear fashion (at least its unclear to > me...I > > tend > > to be rather literal in my interpretations of written requirements), > > and I > > am struggling with defining the actual requirements. > > > > If anyone out there has received this Decision, and believes they > are > > clear > > about what the actual bottom line requirements are, please let me > > know. I > > have muddled through some of the issues, but need some confirmation > on > > a > > couple of points (see the questions below). It may seem to some that > > the > > answers to these questions are straight-forward in the Decision, but > I > > have > > studied this Decision (maybe too much) and find these points > unclear. > > > > 1) Is this Decision only for pluggable equipment type A, or is the > > spark-gap > > / fuse requirement in effect for pluggable equipment type B as well? > > > > 2) Will Denmark, UK, and Sweden accept varistors to ground if the > > circuit > > contains a spark-gap and two fuses? > > > > 3) The installation instructions for our PABX systems include the > > requirement for a permanently connected ground wire between the > > equipment > > ground and an approved building ground (this ground wire is in > > addition to > > the "green wire" lead in the AC mains). This wire is required for > all > > our > > PABX systems (AC and DC powered systems, pluggable type A, type B, > and > > permanently connected systems). Does this permanent ground > connection > > provide an exemption to this Decision? > > > > If this Decision means DK, UK, SE will simply not accept varistors > to > > ground, then a lot of small pluggable type A equipment intended for > > sale in > > DK, UK, SE will have to either: 1) discontinue using varistors, or > 2) > > become > > pluggable equipment type B (which would be onerous, given the IEC > 309 > > plugs > > I've seen). > > > > > > Thanks for the help. > > > > John Boucher > > jpbouc...@lucent.com > > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
