I understand their reluctance, since it is easy to plug both cords into a single 15A/20A outlet. However...
I own a product with such a dual cord system. Albeit, not electronic, but a commercial grade wet 'n' dry carpet shampooer. One cord is for the vacuum system, the other for the heater system. The cords MUST be plugged into different phase outlets. There is a built in LED indicator to let you know when you've found an outlet with opposite phase. The cords are long enough I've never had a problem finding appropriate outlets in my home. This product has all the appropriate safety approvals and is a fairly high volume product. Robert On Sat, 05 May 2007 00:51:00 -0400 Scott Douglas <sdoug...@ptcnh.net> wrote: > Hi All, > > There is a product being safety tested to UL 60065 for > NRTL approval for US and Canada. The "normal operating" > current is 19.88 amps at 132 VAC. The safety agency says > we cannot use a 20 A line cord to power the product > because 15.1.1 says the attachment plug shall be rated no > lower than 125% of the "normal operating" current. I use > the quotes because "normal operating" is a set of > conditions specified by the standard. It is not where the > product will normally operate; the specified conditions > are somewhat artificial to make all products of the type > have the same test conditions. > > The first choice to address the limitation imposed by > 15.1.1 would be to go to a 30 A power cord. > Unfortunately, marketing types say that will not sell. > What they really want is a 15 A cord instead. So a > solution is proposed. Divide the product's electronics in > two parts and use two power cords to supply the product. > The design is such that this is actually a minor change > as most of the parts needed are already there. Just add a > second inlet, circuit breaker, and control PCB. This then > will basically cut the current drawn in half (or actually > 57% and 43%). In this condition, one power cord will > supply about 11.4 A and the other about 8.6 A. Both of > those numbers are less than the 12 A allowed for a 15 A > attachment plug thus satisfying 15.1.1. > > In discussion with our safety lab (one of the big three), > this seems like a viable option. But a sister company's > safety engineer discussed this with his safety lab > (second of the big three) and he was told that they will > not do approvals on a product with dual power cords. When > pressed he was told this was a decision reached between > this agency and another agency (the third of the big > three). One of those unofficially official rules. > > My reading of UL 6500, UL 60065, and EN 60065 does not > turn up any prohibitions against two power cords on a > single product. I am also not aware of any restriction > placed by the US or Canadian National Electrical Codes. > So the question is, are there any rules preventing dual > power cords on a single product? Both would use NEMA > 5-15P 15 A plugs. Are there any gotcha's we need to be > aware of? What am I missing? > > As always, thank you in advance for sharing your > expertise. > > Scott Douglas > sdoug...@ptcnh.net - 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 emc-p...@ieee.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...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com 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 ______________________________________________________________________
