Some wiring can get more complicated. J. R. R. Tolkien's house had 9 rings for the humans, 7 for the dwarves and 3 for the elves. I presume that there was a fairly large circuit breaker for the one ring-main to rule them all. I heard that the electrician kept muttering something about his "precious" being missing when that main breaker tripped.
Ted Eckert Microsoft The opinions expressed are my own and do not necessarily reflect those of my employer or Sauron. -----Original Message----- From: John Allen [mailto:john_e_al...@blueyonder.co.uk] Sent: Thursday, December 15, 2016 11:06 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] British question, about a BS1363 plug-in power supply Ralph Following on from John W's post, some larger properties will have more than 2 ring-mains, plus a number of dedicated branches/spurs/radials for larger loads such as cookers, fixed water heaters and so on. In additional branches/spurs/radials can be used for areas where the ring approach might not be appropriate for physical reasons - such as adjacent sheds, garages and so on - and these would be over-current limited to the cable ratings because the diversity principle obviously cannot be applied. Thus, normal domestic ring main circuits would be required in 2.5mm "twin and earth" cable (another fairly unique UK concept where the grounding conductor is reduced in size) and be protected by a 32A breaker, whereas branch/spur/radial using the same cable must be protected by 16A breakers. BTW: UK fuses and breakers generally follow the IEC standards approach and are rated for continuous running at the stated rating, in contrast to the N.American convention where the fuses/breakers are rated their blow-ratings - thus a 16A UK/IEC breaker can be run at 16A continuous whereas a N.American 15A breaker cannot be run continuously run at 15A. John E Allen W.London, UK. -----Original Message----- From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] Sent: 15 December 2016 18:30 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] British question, about a BS1363 plug-in power supply An interesting design philosophy which has benefits, but it seems to rely on pluggable appliances having an appropriate size fuse in their cordage. You could for example wire an entire house with 3 or 4 of these circuits, rather than a panel full of circuit breakers so common in N.Am Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric *Please consider the environment before printing this e-mail -----Original Message----- From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Monday, December 12, 2016 1:50 PM To: Ralph McDiarmid <ralph.mcdiar...@schneider-electric.com>; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] British question, about a BS1363 plug-in power supply A 32 A breaker connects to a loop of 2.5 mm^2 3-core cable (line, neutral and protective). A large number (there is a limit but it's complicated) of 13 A wall outlets can be connected to this ring, relying on diversity to keep the total current below 32 A. 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. -----Original Message----- From: Ralph McDiarmid [mailto:ralph.mcdiar...@schneider-electric.com] Sent: Monday, December 12, 2016 7:34 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] British question, about a BS1363 plug-in power supply What's a "ring circuit" ? Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric From: Richard Nute [mailto:ri...@ieee.org] Sent: Saturday, December 03, 2016 12:01 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] British question, about a BS1363 plug-in power supply I understood the fuse in the U.K. plug was to protect the power cordage. In the U.K., outlets are supplied by a ring circuit rather than a branch circuit, therefore the power cord could exceed its ampacity (a U.S.A. term). So, if no power cord, no need for a fuse in the plug. I wonder if the power supply has a fuse to protect the power supply. If so, would this count as the plug fuse? Rich From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Saturday, December 03, 2016 5:01 AM To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] British question, about a BS1363 plug-in power supply I received a 5 W SMPS plug-in power supply as part of a multi-unit product. It has interchangeable pins for EU, US, Australian and UK sockets, but it has no fuse. I think this is illegal and intend to notify Trading Standards, as the overall product is marketed by a prominent European company and is widely offered on the Internet. Is there any exemption at all for the requirement that a BS 1363 plug in any form must have a fuse? - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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