John, I believe the issue here is that UL won't allow it without testing. If you are looking to avoid testing, then you have no choice but to use design materials specified by the table. If you are willing to have the design tested, then any enclosure's bottom design complies if it passes the Flaming Oil Test. If the flaming oil does not cause the cheese cloth placed below the bottom openings to ignite, then it passes. I'm not sure of where it is located in UL1950, but in IEC 60 950, see clause 4.6.2 and Annex 5.
Anton (Tony) J. Nikolassy Project Engineer, Electrical Section Factory Mutual Research Corp. Ph: 781-255-4819 Fx: 781-762-9375 e-mail: [email protected] -----Original Message----- From: John Juhasz [mailto:[email protected]] Sent: Monday, October 04, 1999 9:39 AM To: '[email protected]' Subject: Screen Dimensions - Fire Enclosures Hi group. With reference to UL 1950 3rd. Ed., Table 15 (size and spacing of holes in metal bottoms of fire enclosures) , I would like some opinions . . . the largest size listed in the table is 1.00mm minimum metal thickness, 2.00mm maxhole dia., and 3.00mm minimum center-center hole spacing. If my metal thickness was greater (1.27mm), and my center-center hole spacing was 4.75mm, could I not go to a larger hole (3.175 - .125")? The reason I pose this question is that the dmensions I was thinking about using are for a 'standard' punch that a sheet metal fabricator would have. UL told me that what's they won't consider it because it's not listed on the chart. I am trying to tell my mechanical designer to use standard perforated stock which falls within the UL guidelines (there is stuff readily available) but he needs more airflow (without fans) . . . Has anyone been there? John Juhasz Fiber Options Bohemia, NY --------- 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).
