Switch Board/Panel Board — Short Circuit Specification

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Anonymous Poster #1	Switch Board/Panel Board — Short Circuit Specification 03/13/2019 1:41 AM
	The Incoming breaker model is Terasaki - S250-PE, 250 Ampere Frame rated for which Ics is 70kA, Category A breaker The outgoing breakers model is Terasaki - H125 NJ, 125 Ampere Frame rated for which Ics is 85kA,Category A breakers The bus bar rating is 65kA for 1s. How should this panel board be specified, 65kA for 1s??. Since both the Incoming & outgoing breakers are of category A breakers, Is it correct to mention the time rating along with the short circuit? Generally, How is the panel board short circuit is mentioned in the name plate of the board for which the Incoming & Outgoing breakers have different breaking capacity?
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rogerggbr Commentator Join Date: Feb 2010 Location: West Yorkshire, UK Posts: 96 Good Answers: 11	#1 Re: Switch Board/Panel Board — Short Circuit Specification 03/13/2019 10:17 AM
	The way you worded your question suggests this is something you are trying to build. If so you should be referring to IEC61439-2:2011 including all the verifications (comparisons to tests) you will need to do. It would be unusual to see fault levels that high on a board with only a 250A supply, but if that is correct (assuming someone has done a protection study etc) then so be it. In general a board is rated to the lowest rating, either according to the devices, the busbars or the connections. Again all of this is defined in the standard above, assuming it is appropriate for your location. __________________ rogerggbr
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rwilliams Guru Join Date: Jul 2016 Posts: 1367 Good Answers: 105	#2 In reply to #1 Re: Switch Board/Panel Board — Short Circuit Specification 03/13/2019 11:21 PM
	BTW, the 1 second rating would apply to the panel board mechanical structure only, neither of the breakers will survive 1 second at or near interrupting rating
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jmueller Guru Join Date: Jul 2006 Location: Eastern Kansas USA Posts: 1503 Good Answers: 128	#3 Re: Switch Board/Panel Board — Short Circuit Specification 03/15/2019 7:47 PM
	Regarding the time portion, in my experience that is not part of the specification of the panel board's rating. You should have access to the time/current curves for these breakers. I am sure that they will have a much shorter clearing time under the fault condition you mention. Probably in the range of 1-4 cycles or less. Therefore, the 1 second time you mention is not applicable. --JMM
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HiTekRedNek Guru Join Date: Oct 2006 Location: 44.56024"N 15.307971E Posts: 8277 Good Answers: 270	#4 Re: Switch Board/Panel Board — Short Circuit Specification 03/16/2019 9:13 AM
	This guy reminds me of a dialog from a humorous tv show: "Ok, just disarm the bomb." "But I don't know anything about bombs" "That's ok,we will talk your through it: "First,get your 5120-00-596-0864 anti-magnetic screwdriver,and open the cover plate" "I don't have a 5120-00-596-0864 anti-magnetic screwdriver." "What do you have?" "I have two dimes and a penny and a fingernail clipper" "Try the penny" "It's too thick" "Try the dime" "Its too thick too" "Well use the fingernail clipper file." "It's a Phillips screw" "How much time on the countdown timer" "Ten seconds." "Run" If this guy is seeking advice from a forum,I don't want to be nearby. __________________ "A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "To create an apple pie from scratch, first you must create a universe"
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rogerggbr Commentator Join Date: Feb 2010 Location: West Yorkshire, UK Posts: 96 Good Answers: 11	#7 In reply to #4 Re: Switch Board/Panel Board — Short Circuit Specification 03/18/2019 7:09 AM
	That in turn reminds me of the time we delivered a switchboard to a new build project - a large office block/data centre. It had devices in rated 800A and 1000A I think, 50kA anyway, fed from it's own HV/LV transformer. On a site visit (whilst the job was still under construction) one of the engineers there asked if we could test the breakers for him, to demonstrate that they would operate. He actually wanted us to short out the breakers. Our disbelief was off the scale. He was probably one of the civil/mechanical team but even so . . . . We eventually convinced him to drop the idea but they walk among us. __________________ rogerggbr
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Anonymous Poster #1	#5 Re: Switch Board/Panel Board — Short Circuit Specification 03/18/2019 5:47 AM

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Anonymous Poster #1	#6 Re: Switch Board/Panel Board — Short Circuit Specification 03/18/2019 6:53 AM
	https://www.dropbox.com/s/jsinfv0yfanqoex/Panel%20Board%20SC%20rating.PNG?dl=0 For clear picture, check the above link. In the Name plate, the mentioned short circuit rating is, 1) Prospective short circuit current at the location? or 2) Short circuit current withstand capacity of metal enclosure of the panel or 3) Short circuit breaking capacity of the Incomer Main breaker? or short time withstand capacity of Main breaker or 4) Short time current withstand capacity of bus bars?
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Anonymous Poster (2); HiTekRedNek (1); jmueller (1); rogerggbr (2); rwilliams (1)

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