I agree with Joe's comments as well. It is typically very difficult if not impossible to demonstrate the 2 items that Joe mentions below, the only exception being if you can find a material that has a third party (UL) certification that covers the application process as well. Personally, I've never found any such certification. I've run into a desire to use electrical grade paint/powder coat for insulation on bus bars multiple times and have yet to find a good way to make it work such that I can rely on it for compliance to safety standards. Maybe someone else on this forum will have some ideas.
Scott Aldous Compliance Engineer AE Solar Energy +1.970.492.2065 Direct +1.970.407.5872 Fax +1.541.312.3832 Main scott.ald...@aei.com 1625 Sharp Point Drive Fort Collins, CO 80525 www.advanced-energy.com/solarenergy<http://www.advanced-energy.com/solarenergy> From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of IBM Ken Sent: Wednesday, July 18, 2012 6:32 AM To: Joe Randolph Cc: Brian Ceresney; EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: Insulative barriers deposited on metal surfaces I echo everything Joe says. In a recent design we wanted to maintain basic insulation to the inside of a metal chassis. I investigated suppliers who can do conformal coating, etc but in the end it was cheaper/faster to put a die-cut, folded sheet of plastic in the box. On Tue, Jul 17, 2012 at 8:38 PM, Joe Randolph <j...@randolph-telecom.com<mailto:j...@randolph-telecom.com>> wrote: Hi Brian: I work mostly with UL 60950, so I can only offer a few general comments about the use of solid insulation to reduce clearance distances. I have seen several cases where a manufacturer wanted to use a coating of some sort to provide a layer of solid insulation. In UL 60950, the minimum thickness of solid insulation can be as small as 0.4 mm (even less if multiple layers are used), so it seems tempting to propose using an insulating coating of some sort. However, such proposals typically have trouble with one or both of the following limitations: 1) Showing that the required minimum thickness is maintained everywhere, even on corners and sharp edges. 2) Showing that the proposed material will properly adhere to the surface and not crack or flake off. As an alternative approach, you might consider making an insulating cover that sits between the high voltage circuits and the cast aluminum enclosure. The cover would not have to be in contact with either the high voltage circuits or the aluminum enclosure. The only requirement is that it must be interposed into what would otherwise be a troublesome clearance distance. The cover would also have to provide the required minimum creepage distance for paths around the solid insulation, but that is usually not hard to accomplish. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848<tel:781-721-2848> (USA) j...@randolph-telecom.com<mailto:j...@randolph-telecom.com> http://www.randolph-telecom.com<http://www.randolph-telecom.com/> The standards we are typically working with are UL1564, CSA 107.2, and UL2202, however many of the older North American standards have comparatively large distances between live parts and enclosure. These locations are specifically not allowed the easements found in UL840, and instead, the distances must be met, or barriers may be used. Regards, Brian C. From: IBM Ken [mailto:ibm...@gmail.com] Sent: Tuesday, July 17, 2012 4:50 PM To: Brian Ceresney Cc: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: Insulative barriers deposited on metal surfaces It might be helpful for the discussion to know the Standard that applies to the component you are certifying. -Ken On Tue, Jul 17, 2012 at 6:03 PM, Brian Ceresney <bceres...@delta-q.com<mailto:bceres...@delta-q.com>> wrote: Hello Compliance Experts, I'm interested in the use of a high temperature insulator, possibly a ceramic, which would be deposited inside a cast aluminum electrical enclosure. The aim would be to be able to have the product pass safety approvals using this layer as a barrier against electric shock. This layer would help to reduce the large distances required from live parts to conductive enclosure, especially in North America. I'm aware of a variety of processes which can provide electrical isolation, but I haven't seen them used in products having safety approvals. The people who own these processes don't seem to be interested in using them as insulation in products. Has anyone seen this type of approach used successfully, or had success in a similar situation? Any pros or cons you can pass along? Thanks in advance for your consideration. Best Regards, Brian C. Brian Ceresney, CTech. 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To post a message to the list, send your e-mail to emc-p...@ieee.org<mailto:emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ 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 emcp...@radiusnorth.net<mailto:emcp...@radiusnorth.net> Mike Cantwell mcantw...@ieee.org<mailto:mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher j.bac...@ieee.org<mailto:j.bac...@ieee.org> David Heald dhe...@gmail.com<mailto:dhe...@gmail.com> Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848<tel:781-721-2848> (USA) j...@randolph-telecom.com<mailto:j...@randolph-telecom.com> http://www.randolph-telecom.com<http://www.randolph-telecom.com/> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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