Rebekah, If you knew only the power and voltage, then you would use the root of 3 to determine the amps. But since you know the amps, you don't need to use the root. The second equation would be the correct one. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 <http://www.berkeleysolar.com/> www.berkeleysolar.com
_____ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Rebekah Hren Sent: Wednesday, November 16, 2011 9:36 AM To: RE-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] Sizing 3 phase OCPD - main Hi wrenches, I have a question about sizing the main OCP breaker for a panel combining the output of several true three-phase output inverters. To be precise - 10 of the Refusol 20kW, which connect to 480V/277 Y with a max output of 24.1 amps, each inverter has a 3 pole breaker, line a, b, c and a neutral, which doesn't apparently carry any current. Recommended interconnection breaker is 35 Amps. Ok fine, but what should the main breaker and main panel busbar rating be? What I'm not sure about is if this is the right equation for the main breaker in a panel combining all ten inverter outputs: 10 x 24.1A x v3 x 1.25 = 521.8 A or is this the right equation: 10 x 24.1A x 1.25 = 301.25 A The busbar rating should be easy, once I get the main disco OCPD figured out. Main OCPD + (10 x 35) ? 120% busbar rating Thanks for the help! Rebekah Hren
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