NFPA 70, the National Electrical Code, did not require tamper resistant receptacles until the 2008 edition. Many of the versions designed before 2008 were produced to provide an option to home owners who wanted to "baby proof" their homes. The U.S. market was largely made up of people who didn't care if they were hard to use as long as they made it hard for children to stick objects in the receptacles. Since 2008, I've seen more of the major receptacle manufacturers come up with more elegant designs for NEMA receptacles that are easy to use yet prevent inappropriate access to live parts. The best designs open the shutters when force is applied to both the line and neutral openings simultaneously and lock the shutters when a force is applied to only one opening. If you push a plug in straight, it goes into the outlet without hassle. However, a child with a paperclip can't get the shutters open. (However, a determined child with two paperclips might find a way.)
The early GFCI devices introduced into the United States suffered from nuisance tripping issues. It took a few years, but reliability went up and cost came down. I expect the same improvements to occur with tamper resistant receptacles. Let me add one safety note regarding the original question. Although UL 498 requires only a limited number of insertion cycles for testing, it does require the receptacle design to behave acceptably safely under fault conditions. Arcing from loose connections and disconnections must be contained within the receptacle body such that it cannot reach flammable materials outside of the receptacle. The receptacles must also be able to withstand higher temperatures that may be reached either due to arcing or current overloads. My understanding is that within the United States, structure fires are rarely started by arcing within the receptacle. The risk of fire is greater from arcing due to loose connections on the wires connecting to the back of the receptacle, damaged wire insulation near the receptacle or damaged equipment cords and plugs. Ted Eckert Compliance Engineer Microsoft Corporation [email protected]<mailto:[email protected]> The opinions expressed are my own and do not necessarily reflect those of my employer. From: Nyffenegger, Dave [mailto:[email protected]] Sent: Tuesday, May 27, 2014 9:03 PM To: [email protected] Subject: Re: [PSES] "exercising" connections for health? And how many hotels have we been to where the plugs fall out of the wall receptacles, especially in the bathroom? Maybe higher ratings should be a requirement in some cases. But the tamper resistant receptacles I've run into are junk, more like user resistant. -Dave From: Ted Eckert [mailto:[email protected]] Sent: Tuesday, May 27, 2014 9:30 PM To: [email protected]<mailto:[email protected]> Subject: Re: [PSES] "exercising" connections for health? UL 498, the U.S. standard for plugs and receptacles, requires testing for 1000 insertion and removal cycles at the rated load. There is an additional test of 100 cycles at 150% of the rated load. Tamper resistant receptacles, the type now required by the National Electrical Code for many residential purposes, must pass 5000 insertion and removal cycles. IEC 60320 requires 1000 insertion cycles at the rated current and 3000 cycles with no current flowing for the connectors rated more than 0.2 A. These are the minimum ratings. It is likely that some manufacturers have designed their products to perform to specification for a far greater number of cycles. I can conceive of applications that would easily exceed 1000 insertion cycles. One example I can think of would be receptacles in a bathroom. I've known a number of people who plug and unplug a hair dryer daily. Ted Eckert Compliance Engineer Microsoft Corporation [email protected]<mailto:[email protected]> The opinions expressed are my own and do not necessarily reflect those of my employer. From: Ed Price [mailto:[email protected]] Sent: Tuesday, May 27, 2014 5:17 PM To: [email protected]<mailto:[email protected]> Subject: Re: [PSES] "exercising" connections for health? Without sending anyone off on a long search, does anyone have an idea about the number of mating cycles that the common consumer AC power connectors (like the USA NEMA-15 and Euro equivalents) are rated for? Ed Price WB6WSN Chula Vista, CA USA -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: Tuesday, May 27, 2014 9:59 AM To: [email protected]<mailto:[email protected]> Subject: Re: [PSES] "exercising" connections for health? In message <ff616e8a3fc0497bab5fcbb17aaa6...@blupr02mb116.namprd02.prod.outlook.com<mailto:ff616e8a3fc0497bab5fcbb17aaa6...@blupr02mb116.namprd02.prod.outlook.com>> , dated Tue, 27 May 2014, Brian Oconnell <[email protected]<mailto:[email protected]>> writes: > >The immoral of these stories is that a connector, unless specifically >rated for a certain insertion duty cycle, should not be subject to >multiple re-insertion cycles. Components intended to interrupt load >current and/or are rated for multiple insertion cycles should be ok and >will serve the Empire well if used per the mfr's conditions of >acceptability. This is true, but for some widely-used connectors the manufacturers either don't give a clear specification or, for insertions, quote an incredibly low figure, which, if respected, would cause the connector to be rejected. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk<http://www.jmwa.demon.co.uk> Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- 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]<mailto:[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://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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[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]<mailto:[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://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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[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]<mailto:[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://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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[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://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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
