Peter, Some experiences I have had in past lives follow each of your questions. My responses are brief due to lack of time. I hope this helps. Anyone else, please feel free to comment. Best regards, Ron Pickard [email protected]
______________________________ Reply Separator _________________________________ Subject: Rack System Safety (UL1950/EN 60950) Questions Author: <[email protected] (Peter Merguerian)> at INTERNET List-Post: [email protected] Date: 3/9/99 6:26 PM Dear All, I would like to know some of your professional advice on some issues reagrding rack systems to be evaluated to UL1950/EN 60 950. 1. For the North America, does a NEMA 125 V, 20 A plug meet the pluggable B definition? R. I must say no. A pluggable type B plug is of the industrial grade (e.g., NEMA twist lock, IEC309, etc.). Anyone correct me if I'm off base here, but an industrial plug (type B) is not normally found in a residential or light commercial (office) environment. 2. What are some plug configurations which will meet the pluggable B equipment requirements for North America and Europe? R. See above. 3. Does anyone have experience with UL and/or CSA and/or TUV when testing a unit employing a Recognized/Certified/Approved computer type "totally enclosed" power supply? I am interested to know if temperatures should be monitored within such a power supply. So far, I have been asked to thermocouple various points within the power supply and as you all know, it could get very crowded in there. I am interested to know if someone out there knows if such a waiver exists for totally enclosed Approved power supplies. R. Its a pain, I know, but I see no way for you to avoid having to theromcouple points in the power supply as part of your system safety tests. How else are you to verify that the power supply is still within the temperature limits required by the safety standard of your product. 4. When conducting stability tests for rack systems, should all the serviceable card cages be extended out or is it enough to do it one at a time. R. 4.1.1 of UL1950 deals with the subject of stability. If the rack system does become unstable with more than 1 cage extended, then a stabilizing means must be employed or a warning must be conspicuously placed to prevent that. 5. For a CSA NRTLC unit employed in the rack system, does anyone know if the CSA NRTLC Mark is automatically accepted by UL or does UL require that the unit must be re-investigated and placed under their Follow-Up Program? R. I have no experience with this, but UL will likely need detailed information in the form of the equipment's CSA certification report to include test data. After all, if UL allows you to put their mark on your product, I would think that they should want make sure all is ok first. I would suggest that you contact your friendly UL engineer for more details. 6. Has the US Robotics Listed "Sporster" card modem been evaluated to UL1950 Third Edition? R. I have no idea. I would suggest contacting US Robotics and/or look into UL's Recognized Component Directory or "yellow book". 7. Can I List/Certify a rack system to UL1950 Third Edition if the units within it have been Listed/Certified to UL1950 First and/or Second Editions? I do not think so, but am interested to hear your opinions. R. In my experience, I would have to say no. UL1950 1st/2nd Editions are significantly different from the 3rd Edition and even the 3/1/98 revision made significant changes to the 3rd Edition. Doing what you suggest may be mixing apples and oranges. UL should be able to tell you what they need. BTW, see page 11 of UL1950 3rd Edition for effectivity dates. 8. How is a CB test report done for a rack system which consists of previously Listed/Certified/Approved units? Does the CB scheme Recognize the Approvals of the various test agencies (UL/CSA/TUV)? R. In my experience, it's most important that the individual components/sub-systems meet the requirements that would be acceptable to the applicable standard of your product as it relates to the CB Scheme. This can be done as a collection of documents from reputable authorities* such as licenses, approval certificates, test reports, etc., each of which connect the respective components/sub-systems to the requirements. These documents should then be made a part of the greater CB test report. * CB Scheme member NCBs preferred. Thanks in advance. PETER S. MERGUERIAN MANAGING DIRECTOR PRODUCT TESTING DIVISION I.T.L. (PRODUCT TESTING) LTD. HACHAROSHET 26, P.O.B. 211 OR YEHUDA 60251, ISRAEL TEL: 972-3-5339022 FAX: 972-3-5339019 E-MAIL: [email protected] Visit our Website: http://www.itl.co.il --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
