Doug, Here is my personal opinion on your product. View the product as a box within a box. The smaller box is the limited power source (per 2.11). This box must have a fire enclosure. If the small foam spacer is within this box, it must be of HF-2 or better, or exempted per 4.4.3.3 as a "small part which would contribute negligible fuel to a fire".
The larger box contains the fire enclosed limited power source, and the rest of the electronics. Per 4.4.5.2 it does not require a fire enclosure. If the small foam spacer is outside of the power source, but within the larger box, there is no required flammability rating, because it is "outside" the voilume requiring a fire enclosure. My opinion..... George massey_d%[email protected] on 09/29/2000 12:37:00 PM Please respond to massey_d%[email protected] To: emc-pstc%[email protected] cc: (bcc: George Alspaugh/Lex/Lexmark) Subject: Desperate for help on a UL1950 interpretation Hello All - I desperately need some opinions on an interpretation of a particular clause in UL1950. The background: I have an investigation underway to UL1950 of a portable handheld computer, powered by battery and other power options, all of which meet the requirements for inherently LPS. Clause 4.4.3.1 states, "Components inside a FIRE ENCLOSURE........", and continues into flammability requirements of materials and components. Clause 4.4.5.2 addresses components not requiring a fire enclosure, and states, "....-components in a SECONDARY CIRCUIT supplied by a limited power source complying with 2.11, provided that...." The product in question absolutely meets the requirements of clause 4.4.5.2, which I interpret to mean that a fire enclosure is not required. However, the test house performing the evaluation is applying all of the criteria of clause 4.4.3.2. Unfortunately, I have a relatively small foam spacer inside that does not meet the flammability class HF-2 or better as specified in 4.4.3.2. The test house tells me that yes, the product meets the requirements for the exemption allowed in 4.4.5.2, but that I cannot literally interpret the statement in 4.4.3.1 to mean that the substance of clause 4.4.3 regards only component and material flammability ratings inside a fire enclosure. I guess I'm a literal type guy - I can't see any other way to interpret the standard. Can anyone shed some light on this interpretation so that I can read between the lines and understand the real requirements? I'm not trying to make an enclosure of gasoline-impregnated paper, and with the exception of a small (but critical) piece of foam, everything else meets the requirements without the exclusion allowed by 4.4.5.2. HELP !?!? Doug Massey Safety Approvals Engineer LXE, Inc. Norcross, GA., USA Ph. (770) 447-4224 x3607 FAX (770) 447-6928 e-mail: [email protected] Cruise our website at: http:\\www.lxe.com ------------------------------------------- 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]
