Peter, I presume that you replying here for product use in North America only? If the power supply is powered from the ac mains supply and it is intended for use in Europe (and many other parts of the world) then no amount of testing (e.g. to UL 1310) will be able to prove compliance with IEC/EN 60950-1. Of course, it may be that the equipment is Class 1 and relies for separation from mains on Method 2 (Separation by earthed screen) or Method 3 (Protection by earthing of the SELV circuit): note that the old Method 4 - which seemed to me to be what the question from Alexandru Guidea was about - never was permitted in EN 60950, even if it was in earlier editions of IEC 60950. The original question was about meeting LPS requirements in UL 60950 and Angus McGill asked if having such a supply would help in obtaining UL approval for the IT equipment (i.e. ITE). Of course, this is a difficult question to answer without seeing the ITE in question, but given that compliance with the LPS requirements (i.e. Clause 2.5 in IEC/EN/UL 60950-1) means that certain other requirements, such as flammability and openings in transportable equipment, are reduced then the answer must be YES, overall. Angus also asked if it would be just a matter of covering another edge in terms of my company's liability? Again, not a question that anyone could answer with any degree of confidence without knowing the products in question. For one thing it depends on the amount of design and manufacturing control that your company exercises over the products you supply. For instance, it may be that the ITE, at the time of its type-test, did need and was provided with a fire enclosure. We all know that things can go wrong in production sometimes and let us say for the sake of argument that the original design for the ITE was marginal and that subsequently slack manufacturing tolerances or a change in supplier converted a marginal pass into a fail. Of course, these things can always be sorted our by lawyers looking at the fine print of contracts, but that is not much help in supplying goods to important customers and keeping (or establishing) your company's good name. If we look now at 4.7.2.1 (Parts requiring a fire enclosure) second dash we see that, had the supply been a LPS type, then a fire enclosure was not actually required for compliance and so the consequence of the presumed manufacturing defect would be much less severe because the ITE + LPS PSU would still be compliant. Just some additional thoughts for people to ponder and comment upon, no liability accepted for free advice, etc etc... Richard Hughes Safety Answers Ltd
From: [email protected] [mailto:[email protected]] Sent: Monday, May 12, 2003 2:40 PM To: [email protected] Subject: RE: Power Adapter LPS Angus & Doug - Even though 1310 power supplies may only comply with Basic Insulation (per UL60950), they have the bejeebers tested out of them. UL1310 emphasizes testing over construction, whereas UL60950 emphasizes the contrary. Since a UL1310 power supply must meet the requirements for NEC Class 2 power sources, there is no need for any additional testing to demonstrate compliance with LPS requirements in UL60950. The LPS requirements are derived >from (though somewhat less stringent than) NEC Class 2 requirements. Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA [email protected] > -----Original Message----- > From: [email protected] > Sent: Thursday, May 08, 2003 11:24 AM > > One > thing to remember though > is that a Class 2 power supply only requires > basic insulation between > primary and secondary, and most class 2 wall wart > units are built this way. > Depending on what your equipment you should > assess whether this is a > problem for your overall safety strategy. The > class 2 power supply is a > different animal from a Class II power supply as > defined in 60950. > > Regards > > Doug > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc <http://www.ieeecommunities.org/emc-pstc> This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
