Hello Brian, I've worked on products with this type of power input and it isn't a difficult issue for certification. You have the basic idea of what is needed. One suggestion is to search UL 60950-1 for "multiple power sources". (There are U.S. national differences, so you will need the UL standard, not the IEC standard.) You do not necessarily need to tie the handles of breakers together; you can have separate disconnects as long as the marking and instructions are clear. You can also use the plugs as disconnects. However, I foresee possible problems as you describe the product.
This configuration is most common where the two inputs are different voltages. You will have one significant problem if you have two NEMA 5-15P cords; the installer will try to plug both into the same circuit through a duplex outlet. If the continuous current draw of each is over 6 A, and if the equipment isn't considered movable, an AHJ may want each plugged into a single-outlet dedicated circuit. Now you are back to new facility wiring. The instructions and marking will need to clearly indicate that the plugs need to go to separate circuits. NRTLs may give you a hard time on this and certification may not be easy. In many facilities, all of the outlets along one wall will be off of the same circuit, and the installer would be forced to use an extension cord to get to another circuit. In my opinion, the correctly sized plug for a single circuit is better. I know it's a hassle to require customers to wire a new circuit, but it reduces the risk of improper installation and tripping breakers. Ted Eckert Compliance Engineer Microsoft Corporation [email protected] The opinions expressed are my own and do not necessarily reflect those of my employer. -----Original Message----- From: Kunde, Brian [mailto:[email protected]] Sent: Thursday, June 02, 2011 5:40 AM To: [email protected] Subject: Dual Power Cords We have received a request by our customers to change our product (about half the size of a household refrigerator) from one high current power cord (plug/receptacle/branch circuit) to two power cords using standard 15 amp receptacles (on separate circuits) to avoid having to do special facility wiring for the high current receptical. What safety considerations are there in doing this? Internally, one circuit would power a heater, the other would power our electronics. The circuits are not separated in any way in the enclosure so both AC Mains circuits or power cords will have to be disconnected to make it safe to service. Your input would be appreciated. Here is what we are thinking: 1. Input rating labels by each power entry location. 2. Warning label to remove BOTH power cords before servicing. 3. Using two dual pole circuit breaker/switches (disconnect device) mechanical linked together so when you turn off the switch all circuits are powered down. Is this doable? Thanks, The Other Brian ________________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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]>
