Main Breaker Based on 3Ph or 1Ph

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Anonymous Poster	Main Breaker Based on 3Ph or 1Ph 01/03/2011 12:35 AM
	As we know that 1Ph draw more current and 3Ph draw less current to balance the VA rating.I have some confusion during load calculation. In 3 phase panel load center, some load as a single phase(2P breaker,Ph&N) and some load as a 3Ph(R,Y,B),so our final load calculation based on 3ph(square root 3) or 1Ph for main breaker,. So could any one tell me the answer
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pnaban Guru Join Date: Jun 2010 Location: srilanka Posts: 2725 Good Answers: 5	#1 Re: Main breaker based on 3Ph or 1Ph 01/03/2011 1:04 AM
	Connect a power analyser and record Amp drwan in each phase during working hours and decide the rating of CB.If load is unbalanced you should balance it. __________________ pnaban
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#2 Re: Main breaker based on 3Ph or 1Ph 01/03/2011 4:09 AM
	The breaker must be sized so as to prevent the cables taking too much current. British Standard 7671 tells all. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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rhkramer Guru Join Date: Oct 2010 Posts: 1294 Good Answers: 35	#3 In reply to #2 Re: Main breaker based on 3Ph or 1Ph 01/03/2011 2:25 PM
	PWSlack is correct, but I'd amplify his answer a little (I did give him a GA): The NEC also "tells all". The outgoing breakers from this panel are sized to protect the conductors going to the loads. If you also want more precise protection (like for a motor), you need to use supplementary protection (like a motor starter with overload protection).
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pnaban (1); PWSlack (1); rhkramer (1)

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