Doug, A long long time ago, and not with the present company, I was submitting a new product very similar to one that was already UL Listed (using the same chassis, enclosure, and power supply) but with different cards installed, when......
.....during UL testing and evaluation at our facility we first smelled something burning, then we saw a wisp of smoke, then, immediately the smoke turned to a dark 3-inch column, at which point I literally pulled the plug! The UL inspector stood up, looked at me and said there was nothing left for him to do, and to call him when we were ready to perform some serious tests. After swallowing my embarrassment and doing some research I noticed that the power supply specifications stated that it required x-amount of clearance on at least three sides. In the first Listed model, that was the case, and the product had no problem going through all the UL tests. In the second instance, the cards in the card cage were right against the power supply and shut off that required clearance. Thus, we literally choked the supply so that it overheated. The moral: don't get cocky just because you have passed UL tests with one version and therefore neglect to perform preliminary test with a new configuration. I know,-- time was of the essence and the schedule was pushing us rather than us pulling the schedule. Well, we quickly found another power supply, since the cards could not be moved because they were in a dedicated location, I performed preliminary tests to make sure everything was O.K., and called the UL engineer back. A lot of hard work, but it was worth it. (Do it right the first time!) This is just one graphic example why a "Recognized" component needs to be further evaluated in each and every application. Tania Grant, [email protected] Lucent Technologies, Switching Solutions Group Intelligent Network and Messaging Solutions -----Original Message----- From: Doug [ mailto:[email protected] <mailto:[email protected]> ] Sent: Friday, October 20, 2000 9:11 PM To: [email protected] Subject: Re: Got a beef with an NRTL ... The cert house which approved the power supply is the -> exact same one <- to which we took our product. I do not want to get any more specific about which NRTL it is for some obvious legal reasons. Apologize for the vagueness. I'm getting some good replies from people. But I can't for the life of me figure out why when a component is approved for a certain application and that component is used in that certain application, the approval for the component is rejected. The grounds for rejection is based on the fact that an AC fuse is being used for input protection inside the power supply. That point I can understand. But, the use of an AC fuse in the input should have been rejected when the power supply first was tested. - Doug ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
