Be careful Joe, There is a UL PAG that says that PoE must be treated as a TNV1, but overvoltage tests can be waived from Annex NAC. It is a botched PAG that needs to be fixed for other reasons. Also if it crosses the boundary between buildings it needs to be treated as TNV-1 even for international safety standards which may impose creepage and Clearance distances.
Also people forget there can be a lot of current coming from a shared PoE DC supply and eventhough safety requirement creepage and clearances do not apply between the high and low voltage rails it is good to impose separation so you don't have a fire. Jim Jim Wiese Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) [email protected]<mailto:[email protected]> ________________________________ From: Joe Randolph [mailto:[email protected]] Sent: Monday, November 26, 2012 1:43 PM To: [email protected] Subject: Re: [PSES] POE creepage & clearances Hi Ian: I think the short answer to your question is that under 60950 there are no requirements for creepage and clearance distance between the Ethernet circuit and ordinary SELV circuits that are user-contactable. This is because under 60950, Ethernet is classified as an SELV circuit. There are no requirements to separate one SELV circuit from another. Where this issue becomes confusing is that under the Ethernet 802.3 standard, an Ethernet port must provide a 1500 VRMS isolation barrier between the Ethernet conductors and earth. This is a legacy requirement whose origins seem to have been lost in the sands of time. However, I believe the consensus view is that the original intent of this requirement was to protect against ground loops and was not related to user safety. Nevertheless, the 802.3 isolation requirement has sometimes been treated as though it is a safety requirement. Note that the 802.3 requirement is for a simple dielectric test, with no reference to creepage, clearance, or distance through solid insulation. So, in principle, there are no safety isolation requirements for your application, since both of the proposed power supplies have a SELV output. This makes the entire device a SELV circuit (unless there are other ports on the device that are not SELV). Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com<http://www.randolph-telecom.com/> Dear colleagues We are developing a hand held product that is powered from +48V DC over Ethernet or from an external +12V DC wall wart PSU. The maximum internal voltage will be the +48V POE. Can anyone let me know what the creepage and clearance requirements between the ?primary? Ethernet circuit and the ?secondary? circuit. The product will be tested to IEC 60950 or possibly IEC 60065 so I am assuming a safety isolation creepage & clearance is required. Many thanks in advance; Ian McBurney Design Engineer Allen & Heath Ltd Kernick Industrial Estate Penryn, Cornwall TR10 9LU United Kingdom +44 (0)1326 370121 [email protected]<mailto:[email protected]> www.allen-heath.com<http://www.allen-heath.com/> A DMH Pro Company<http://www.dmh-global.com/>. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
