Brian, I will concentrate on replying in connection to EN 60950-1 and let others confirm, or otherwise, applicability to EN 601010-1. I would suggest first of all that you look at the first edition of EN 60950-1 rather than the third edition of EN 60950, unless you have a good reason to use to older standard. If you're starting out on a new product development then using the latest standard will provide you with the longest time period before you need to re-evaluate your product against the superseded standard. Temperature limits are now given in section 4.5 and you will see that the standard has changed from specifying temperatures rises to absolute maximum temperature. IEC/EN 60950 have never assumed a normal ambient of 40 degC, previously it was 25 degC (see 1.4.12 in the 3rd edition) [the 40 degC requirement comes from 1.4 of 1010-1]. Getting back to the first edition of EN 60950-1 and you will see (1.4.12.1) that temperature measurements are made (or converted) to the manufacturer's maximum operating temperature - with a minimum operating temperature of 25 degC (i.e. if you say that your equipment is designed only for use outside in the Artic then the tests will still be run at + 25 degC and not -.40 degC/F, even if your spec does specify a max ambient of -40 degC). EN 60950-1 addresses itself primarily to faults within the equipment rather than to external faults. It is therefore my view that it would be incorrect to apply any fault condition limits the instant that the ambient temperature exceeds the specified maximum. Following such an approach in the extreme would mean that the moment your ambient temperature rose from 30 degC to 30.001 degC that you would apply the fault condition limits (I did say the example was in the extreme, to make the point). Of course this is ridiculous, but I use it to illustrate the point that standards should be an aid to common sense, not a replacement. Irrespective of the foregoing, there are no temperature limits for accessible parts under fault conditions specified in EN 60950-1, there are only temperature limits applicable for windings: this is an omission presently being looked at for future amendments to this standard. Compliance with standards should also only be a first (and generally very necessary) step. There is also potential customer satisfaction to consider. I suggest to you that many, and probably the vast majority, of people would expect equipment to run warmer in the event that the air conditioning fails but they would not expect equipment to get so hot that it became a burn hazard. Although not a safety matter, many/most customers would probably expect your equipment to turn itself off in such obviously foreseeable conditions rather than burn itself out (even if it did so without becoming overly hot). By pointing to the spec. and saying 'there, it says that the max temp must not exceed 30 degC and your room got to 30.1 degC so the warrantee is no longer valid' may get you off the contractual hook, but it isn't likely to get you repeat orders! Hope the above helps. Richard Hughes Safety Answers Ltd (but expressing own views only)
From: [email protected] [mailto:[email protected]] Sent: 24 April 2003 15:16 To: [email protected] Subject: Surface Temperature Limits Greetings to all, In EN61010-1 section 10 and EN60950 safety standards, there are surface temperature limits specification for Normal Condition based on an Ambient Temperature of 40C. Our company makes analytical instrumentation and a new product we are working on is functionally very susceptible to room temperatures. So, the operational specification in our manual says it must be in a room no warmer than 30C. Question is, is it proper to consider surface temperatures for safety based on a 30C ambient which would give us 10 more range to work with? Someone told me you could do this but it doesn't seem right to me. You are relying on the building's air conditioning as a level of protection. Then I was told that if the AC broke down it would be considered a Fault and then the 105C limit would be applied. Is this correct thinking? Knowing the correct way to apply these requirements effect the design of our instruments so it is important for me to know. Thanks to all in advance. Brian Kunde LECO Corp. 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
