There may be a “disconnect” between SDO (standards development) and code writing panels at the NFPA. For example, the 125% rule in Article 690 is there because the NFPA thinks that the standard test conditions for solar panels aren’t realistic. They think 1,000W/sq-m irradiance is too low, and short circuit PV currents need a 1.25 multiplier.
Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric From: Ted Eckert [mailto:000007cf6ebeab9d-dmarc-requ...@ieee.org] Sent: Tuesday, October 10, 2017 1:58 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] NEMA 5-20P with IEC 60320 C13 The various clauses of NFPA 70 are reviewed, challenged, debated, argued and rewritten. I don’t think the clause in question remains because nobody has challenged it. Part of the issue is that the electrical infrastructure in the U.S. has been developed around this rule. If affects circuit breaker trip curves, conduit fill, wire sizes and rating and many other aspects of a building’s electrical system. If the rule were changed, would there be problems switching over? Would you have overheating in older structures where circuit breakers were replaced without updating wiring? Wold there be other effects of mixing 80% and 100% rated components? How many U.S. national standards would need to be updated? It is a poor analogy, but think about switching sides that you drive on the road. Sweden switched on September 3, 1967. Street signs, traffic signals and road markings all had to be changed. Headlights had to be adjusted or re-aimed. For quite a while, there was a mix of left-hand and right-hand drive cars. It was a massive undertaking for a country with fewer people than either London or New York City. Changing the way branch circuits are rated in the U.S. could be done, but it would be an extremely complicated undertaking. The risks of a mismatch of circuits, circuit protection and loads would be significant for a long time. I suspect that by the time the technology evolved to the point where the requirement could be eliminated, it was too late and eliminating it would result in too much expense and rework. Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer. From: John Woodgate [mailto:j...@woodjohn.uk] Sent: Tuesday, October 10, 2017 12:49 PM To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] NEMA 5-20P with IEC 60320 C13 Well, yes, because the IEC tends to believe that rated values are realistic and do not need to be adjusted downwards. I suspect that at some point in the distant past (maybe even nearly 100 years ago), some connectors in wide use were found to overheat at rated current, so the 'derating rule' was brought in, and no-one has challenged it since. John Woodgate OOO-Own Opinions Only J M Woodgate and Associates https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.woodjohn.uk&data=02%7C01%7Cted.eckert%40microsoft.com%7Cb9a5abba70d24e2f093e08d51018031b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636432617679408094&sdata=jNpj%2FFhCHx9ir37o7Xf5GxovOe2h0nU9FIZnbo5mItE%3D&reserved=0 Rayleigh, Essex UK On 2017-10-10 20:12, Ralph McDiarmid wrote: The NEC (NFPA 70) talks about “continuous currents” and when to apply the all-too-familiar 125% rule. Canadian Electric Code (CSA part I) has same requirement. The IEC seems to have avoided it. Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric D 604-422-2622 From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Monday, October 09, 2017 8:31 AM To: mailto:EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] NEMA 5-20P with IEC 60320 C13 It is my understanding that according to the US National Electric Code, 15 amp receptacle are derated to 12 amps max., and 20 amp receptacles are derated to 16 amps. IEC 60320 C13 connectors are rated 15 amps in North America. Do I derate them as well or can I draw 15 amps continuous from the C13 connector? So here is the big question: If I have a power cord with a NEMA-5-20P at one end, IEC 60320 C13 at the other end, and 14awg cordage (rated 18A), can I use/ship this power cord with a product rated 15 amps? Thanks to all. The Other Brian ________________________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. 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