My attempt to put aside the access rules got in the way of the question. Another way of putting it is, if you have a solid top which overhangs the bottom by the 5 degrees, there is no limit to the size of the side opening. It appears the opening can be the size of the side. In other words, is there some undeclared maximum to dimension L in Figure 4D?
Bob [email protected] wrote: Hi Bob: Been there, done that. Regardless whether the requirements for side and top openings APPEAR from the text to be for prevention of electric shock, they also apply to fire enclosures. The way the standard is written, the text appears to not require a fire enclosure for the sides and top. Clearly, this is an oversight in the writing of the standard. If you submit the construction for certification, you will find that the cert house will impose the side and top opening requirements. Or... you can perform the fault-all-components test and qualify the construction as not needing a fire enclosure. This was my solution. Best regards, Rich From: [email protected] [mailto:[email protected]] On Behalf Of Robert Johnson Sent: Friday, June 01, 2007 6:18 PM To: ieee Subject: IEC 60950 fire enclosure openings I have come up with a question and will try to strip it to its essentials. Consider a part which requires a fire enclosure, as a hypothetical example a primary rectifier bridge with reinforced insulation. It is safe to touch, with no live parts, so top openings or side access is not restricted. A bottom enclosure is provided out beyond the 5ยบ projection. The question is what is the fire enclosure? Clause 4.6.1 places no limits on side or top openings since access is not an issue. In fact it appears the opening can extend from the bottom up the sides and over the top and down the other side to the bottom. Is it necessary for a fire enclosure to envelope the part? The next difficult question is what is a part placed in this opening? If parts are placed in the opening (anywhere beside or above the part requiring the fire enclosure), they must be V-1 (etc. see 4.7.3.2), but if outside the opening they may be HB (etc. see 4.7.3.3). No distance is specified, so in my case it appears a plastic window 12 inches away appears to be occupying an opening in an enclosure. I can apply 4.7.1 method 2, but do the enclosure requirements of method 1 fail to be usable in this situation? Any opinions? Robert Johnson ITE Safety - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
