Will is correct. I have gotten around this type of fan issue in the past by simply running the normal heating test with the fan disconnected. If you can pass normal temperature rise limits without the fan then your argument becomes easier as the fan is no longer "critical", it is simply a design robustness feature at that point.
For the device to operate normally and to operate within the limits are not always the same. Josh -----Original Message----- From: Brown,William [mailto:[email protected]] Sent: Friday, December 13, 2013 8:52 AM To: [email protected] Subject: [External] Re: [PSES] Cooling fan safety query A locked rotor test is considered an abnormal and measured temperatures are allowed to exceed the limits for normal operation. If that happens, then it proves a minimal amount of airflow is required to maintain safe temperatures and minimal CFMs become required. That said, I've never seen a CPU fan be the make or break for safe temperatures (except maybe a laptop). It is likely you have a (written or unwritten) standard operating procedure that states what must be called out for fans and an engineer that is either unwilling or unable to justify removing the requirement. After all, it is hard to find a regulatory engineer that can do both. -Will William L Brown Jr. / Engineering Manager - Regulatory and Compliance / Tyco Security Products Tel: +1 978 577 4205 / Mobile: +1 978 727 7069 6 Technology Park Drive / Westford, MA 01886 / USA [email protected] / www.tycosecurityproducts.com/SocialMedia.aspx / www.tycosecurityproducts.com Access Control, Video, Location-Based Tracking and Intrusion. UNIFIED. CONFIDENTIALITY NOTICE: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information or information otherwise protected by law. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. Any applicable rights to privilege have not been waived. . -----Original Message----- From: McBurney, Ian [mailto:[email protected]] Sent: Friday, December 13, 2013 8:55 AM To: [email protected] Subject: Re: [PSES] Cooling fan safety query John; I agree the airflow rates will vary with applied voltage and blade profile but if the product continues to function "safely" with a stalled rotor why does it have to be listed in the critical component list. Regards; Ian McBurney Design & Compliance Engineer. Allen & Heath Ltd. Kernick Industrial Estate, Penryn, Cornwall. TR10 9LU. UK T: 01326 372070 E: [email protected] -----Original Message----- From: John Allen [mailto:[email protected]] Sent: 13 December 2013 13:31 To: McBurney, Ian; [email protected] Subject: RE: [PSES] Cooling fan safety query Ian I think the critical factor may be the airflow rates at the reduced voltages as this may well vary between various ostensibly similar fans of the same nominal voltage. The actual airflow patterns from the outputs of the various fans may also differ due to differing blade profiles, etc. Regards John Allen Compliance with Experience W.London. UK -----Original Message----- From: McBurney, Ian [mailto:[email protected]] Sent: 13 December 2013 11:05 To: [email protected] Subject: Re: [PSES] Cooling fan safety query John; I believe the fans are listed for the flammability of the plastic body but I may be wrong. Ian McBurney Design & Compliance Engineer. Allen & Heath Ltd. Kernick Industrial Estate, Penryn, Cornwall. TR10 9LU. UK T: 01326 372070 E: [email protected] -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: 13 December 2013 10:34 To: [email protected] Subject: Re: [PSES] Cooling fan safety query In message <80f690de07894e049b221728b4a99...@dbxpr07mb206.eurprd07.prod.outlook.com> , dated Fri, 13 Dec 2013, "McBurney, Ian" <[email protected]> writes: >We have to use alternative fans due to supply issues and this incurs >considerable test agency costs as the agency won?t accept a >manufacturers range of fans without testing each one. On what grounds are they re-testing when the fans are UL-listed? -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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