I've had experience with this in a few types of products, using both with IEC-based standards and old school UL standards. When dealing with various electric codes such as NFPA 70, there are needs that must be met and the design of a product must be compatible.
As you have stated, there is very little mentioned in product safety standards. Sometime you will see a "pull out test" or some such thing and clearance and creepage requirements still apply. But we seldom find requirements or guidance to the level of detail you are asking about. This tends to foster some rather bad habits by design engineers. For example, I had to put the kibosh on a "star ground" where the engineer had placed a metallic standoff in a circuit board and proceeded to screw down at least eight ring lugs all fanned out around the circle, making a perfect star burst of wires. The whole assembly was unwieldy and very slippery under the fastener. It simply would not hold to a simple finger torque out test. So then the engineer attempted to put all eight wires in a single oversized ring lug. Doing a wire pull out test resulted in one or two of the wires immediately pulling free and subsequently all fell out. While it was possible to get specific crimps to pass these simple tests, it was not manufacturable in an ongoing basis. Our solution was to leverage IPC-WHMA-A-620A Requirements and Acceptance for Cable and Wire Harness Assemblies. This is not specifically mentioned in many safety standards and therefore does not have a lot of force behind it, but it is very familiar to wire and cable houses who are in the business of making cable harnesses. Also, most company reliability engineers will agree with this document. It has very specific inspection criteria based on the "acceptance class" you need. I find Acceptance Class 2 is sufficient for most products and also very cost effective. For the situation you brought up, I have always required no more than one or two conductors in a single crimp terminal of any kind and no more than two ring lugs per fastener. IPC 620 has requirements that require inspection of the wire strands on the far side of the wire crimp portion and for the wire insulation under the insulation crimp portion. For example, IPC 620 makes statements like this, "*When attaching multiple wires to a single terminal, each wire shall meet the same acceptability criteria as a single wire termination. When attaching single or multiple wires to a terminal the combined circular mil area of the wires shall comply with the circular mil area range for the terminal*" and "*If multiple wires are used insulation from all wires extend past the insulation crimp ...*". In one place, "*Two wires into a single contact ..." *is listed as a defect, "*unless the contact or connector specifications indicate that this is acceptable.*" Hope this helps, Doug Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 On Tue, Feb 21, 2017 at 7:12 AM, John Woodgate <jmw1...@btinternet.com> wrote: > It only helps to show that this is a 'grey area', suggesting that for a > quiet life, do not use more than one wire. > > > > In practice, two solid wires are very troublesome, but two stranded wires > are nowhere near as difficult. The more strands the better, within the > capacity of the crimp. > > > > With best wishes DESIGN IT IN! OOO – Own Opinions Only > > www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England > > > > Sylvae in aeternum manent. > > > > *From:* Adam Dixon [mailto:lanterna.viri...@gmail.com] > *Sent:* Tuesday, February 21, 2017 1:48 PM > *To:* John Woodgate <jmw1...@btinternet.com> > *Cc:* EMC-PSTC@listserv.ieee.org > *Subject:* Re: [PSES] crimp hardware for multiple conductors? > > > > Thanks, John. > > IEC 60352-2 Section 10.2 "Crimped connections made with more than one wire > in a crimp barrel" briefly addresses general considerations and closes with > the requirement for full testing to Section 5.3.3. There is an additional > comment "in some industries, the use of more than one wire is deprecated." > which doesn't help. All of the illustrations in the standard are single > wire, too. ;-) > > > Cheers, > > Adam > > > > > On Tue, Feb 21, 2017 at 8:02 AM, John Woodgate <jmw1...@btinternet.com> > wrote: > > IEC 60352-2 may help. Or not. > > > > With best wishes DESIGN IT IN! OOO – Own Opinions Only > > www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England > > > > Sylvae in aeternum manent. > > > > *From:* Adam Dixon [mailto:lanterna.viri...@gmail.com] > *Sent:* Tuesday, February 21, 2017 12:45 PM > *To:* EMC-PSTC@LISTSERV.IEEE.ORG > *Subject:* [PSES] crimp hardware for multiple conductors? > > > > I would appreciate pointers for locating ring and quick disconnect crimp > hardware which are approved for multiple conductor use. > > I've had conversations with two major manufacturers so far. One confirmed > a quick disconnect terminal family that supports multiple conductors > provided that the summed cross sectional area (CMA) is within spec. The > other said that they don't have any such hardware. The conversations > occurred after sorting through datasheets, tracking down crimp guides, > looking at qualification data, etc. My search method may be sub-optimal > and I am open to suggestions. > > I am more interested in ring terminals at this point. Feel free to reply > off-line if there are an issues with mentioning supplier names. > > I also read these archive threads where it appears that crimping has been > discussed to some extent, but I didn't catch any "multiple conductor per > crimp" commentary. > > 2015 "Shrink-wrap on soldered connections" > 2004 "EN 60950 earth terminal requirements" > 2001 "Double Crimp - History Request" > 2000 "Double Retention" > 1999 "Ground lugs" > > Thanks! > > -Adam > > - > ---------------------------------------------------------------- > > 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 < > 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://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > > > - > ---------------------------------------------------------------- > > 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 < > 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://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > -- Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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 <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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
