Hello Mike, Single-pole switches are acceptable and typical on plug connected single-phase equipment and sometimes on two-phase equipment. IEC 60950-1 has the somewhat cryptic marking “Double Pole/Neutral Fusing” as indication to service personnel that there may still be live voltage in the equipment even if the switch is off. The symbol is even more cryptic to the average person, but the warning is specified. The intention for plug connected equipment is that the plug serve as the disconnect. Service personnel are to unplug the equipment for servicing to remove all power. You may even have equipment that is rated 208/240 V. In Europe, it would be plugged into line and neutral whereas in North America, it would be plugged into two phases of either a split-phase 120/240 system or two phases of a 120/208 three-phase system. In North America, the switch would never remove voltage from within the equipment but would interrupt current. This is still generally acceptable for plug-connected equipment.
Field-wired/permanently connected equipment would require a main disconnect that opens all phases. The installer should be aware of the polarity of the system and the installer should not reverse phase and neutral during wiring. In North America, this allows an equipment disconnect that opens the phases without opening neutral. As such, even with field-wired equipment, it is permissible to have neutral bypass the main disconnect. It has been a while since I had to delve deeply into the electrical codes, so I may be a little off on the field-wired requirements. I encourage any of our esteemed contributors to correct my errors. Best regards, Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily represent those of my employer. From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Saturday, January 28, 2017 8:32 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Double Pole Mains Switches, Cord Connected Products ALL European 2-pin 6 A plugs are reversible, and 3-contact plugs used on the Continent are reversible (there are two kinds, one with 2 power pins and side-contact for earth (called 'Schuko') and one with a third pin for earth). The standards you cite are written so that the product is safe, whichever way round the plug is inserted. You do not need a double-pole switch; in fact that can be a disadvantage, as it brings the two power conductors close together in an assembly with mechanical movement. A short-circuit at some stage in the life of the device is not improbable. Also, the insulation can fail, usually with smoke and small-scale flame, accompanied by a loud noise. With best wishes DESIGN IT IN! OOO – Own Opinions Only www.jmwa.demon.co.uk<http://www.jmwa.demon.co.uk/> J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. From: Mike Sherman ----- Original Message ----- [mailto:msherma...@comcast.net] Sent: Saturday, January 28, 2017 4:17 PM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: [PSES] Double Pole Mains Switches, Cord Connected Products Because of the lack of polarization on many 2 pin European plugs, I have always recommended double pole mains switches on cord connected products for the EU market. However, I am not finding support for this in standards such as 60335-1, 60601-1 or 62368-1. Your thoughts will be appreciated, oh experienced group, on: --safety issue involved --standards that do require double pole (sometimes referred to as "all-pole") mains switches. Mike Sherman Graco Inc. - ---------------------------------------------------------------- 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 <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>
