Kris, If you have an electronic copy of the standard, do a search on "IT" and determine if the clause is applicable. For instance, if you do so with IEC 60950-1, 2nd Edition, you will hit on 1.5.8, concerning components connected between line and earth. Not applicable. Next is a installation manual note in 1.7 as to whether your equipment has been evaluated for IT systems--hold the thought there. Then you go to 2.7.4, or overcurrent protection. The clause says that you don't have to be concerned about protection against earth faults if you do not have an earth connection, and you only need one protective device against overcurrent. Next is 3.4.6 concerning disconnects. The wall plug-in unit is your disconnect. Next, and possible most significantly, if your Class II unit had a heater, 4.3.7 would require a temperature-sensing device to disconnect both the line and neutral conductor. I suspect your plug-in unit contains no heaters, but if it did, and you only had only one cutout, you can still draw current through the unprotected supply lead to earth even after the line conductor cutout opens if your impedance to earth is not infinite in the IT circuit. Lastly, you go to 5.1.3, or touch current, and since this section does not exempt Class II products, you have to consider touch current and the applicable circuits in IEC 60990.
Going through the above, I would say yes, you can consider IT supplies for Class II wall-plug in units under IEC 60950-1, but there is probably no impact. Regards, Don Gies, N.C.E Senior Product Compliance Engineer Alcatel-Lucent Murray Hill, NJ 07974-0636 USA From: Carpentier Kristiaan [mailto:kristiaan.carpent...@thomson.net] Sent: Friday, October 05, 2007 9:59 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: Class II PSU for IT power systems Brian, I am referring to IT power distribution system and a class II wall plug, thus w/o a PE pin. My assumption is that this wall plug does not have to comply with additional requirements related to IT power distribution system because there is no connection to PE. Nevertheless, some CB reports state that tests have been done on the wall plug for IT power distribution system and some other don't. Best regards, Kris Carpentier Regulatory & Approvals From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Brian O'Connell Sent: vrijdag 5 oktober 2007 15:50 To: emc-p...@ieee.org Subject: RE: Class II PSU for IT power systems If I am not missing something obvious, the construction answers the question. Class II construction does not have to depend on a protective earth for protection against shock, so there is no need for the ground pin. Perhaps we have a 'terminology disconnect' - are you referring to an "IT power distribution system", or perhaps a "Class 2 output" ? Note that for connection to an IT power distribution system (which could be either isolated or separated by some impendence from any 'system' earthing), it may not be possible to clearly indicate the earthed conductor to mains, so there are additional requirements for mains disconnect. I have advised designers, for equipment designed to be connected to an IT power distribution system, to not rely on any ground bonding for protection against shock. Additional note - UL listings will sometimes indicate "IT Power Source"; this is NOT referring to an IT power distribution system. luck, Brian > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf Of > Carpentier Kristiaan > Sent: Friday, October 05, 2007 2:18 AM > To: emc-p...@ieee.org > Subject: Class II PSU for IT power systems > > Hi Group, > > Does it make sense to test a Class II wall plug PSU for IT > power systems > as there is no PE pin on such a PSU? > Some CB reports mention that testing for IT power systems is done and > some don't. > > Best regards, > > Kris Carpentier > Regulatory & Approvals - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This e-mail has been scanned by MCI Managed Email Content Service, using Skeptic(tm) technology powered by MessageLabs. For more information on MCI's Managed Email Content Service, visit http://www.mci.com. ______________________________________________________________________
