Hi, Camille. > From: Camille Good > Sent: Wednesday, September 14, 2005 1:07 PM > > Actually, I think you are outside of Class 2 limits > with 24 Vac 5 A, as the limits of Class 2 are maximum > 30 Vac / 42.4 Vdc
Although you are correct about Reginald's needs exceeding Class 2 limits for wet locations (his original post indicates as much), I would like to point out that Class 2 limits are not quite as described. For wet environments, the voltage limits are 21.2 Vpk and 30 Vdc. Reginald - While your assessment is generally correct, you're likely to have a *very* difficult time finding a Class 3 supply or transformer with the ratings you mention, since Class 3 current limits are at 150/Voc, and assuming a near 30 Voc >from a 24 Vac transformer/supply, the maximum output current is required to be 5 A or less. That's a tough nut to crack. Please pardon my relating a memory: I have met one character, who in about 1987 worked for Honeywell (and I at UL, testing, among other things, Class 2 transformers), that designed a transformer beautifully at the hairy edge of Class 2 (dry location) limits, using a core size more closely matched to 1 kVA and wire sizes typically used for much larger current output transformers. I told him it couldn't possibly pass muster, but in the end had to eat crow. All this by manipulating a core air gap; the large core and wire sizes had the thing barely over ambient under short-circuit conditions for eight hours (part of my customers design intent). Impressive bit of trickery ... er ... I mean engineering. Wish I could remember his name. Regards, Peter L. Tarver, PE [email protected] - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium 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/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
