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Main CB

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Hello everyone, I came across conflicting answers to my question. In my panel there are three breakers 6A for the power supply(it is writing in manual) and 5A for drive1 and 5A for drive 2.(writing in manual) The panel must meet the requirements of UL508. I think the main breaker should be  not less than 16A. or 16 A Exactly. The rating plate should also show 16A. Am I correct in my calculations?  Thank you!

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According to  Reference to UL 508A Section 32.3.1a found in this presentation https://www.eaton.com/ecm/groups/public/@pub/@europe/@electrical/documents/content/pct_2930585.pdf  you need to use 6A (the largest breaker} plus the FLA of Drive 1 and the FLA of drive 2.  And then go to the closest size above that. so in your case assuming the breakers are at drive FLA you would use 20.  But if the drive FLA ar say 3.5A and 6 + 3.5+3.5 gives you 13A then a 15A breaker would be called for as the main.  

This is at least how I would interpret UL508. 

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