<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div><span>Hi rebecca, I assume the inverters are all true 3 phase, to check 20 kW/480/1.73 = 24 amps this is what you expect on each leg. You have 10 of these therefore 240 amps on each leg. Solar is continous so you need x1.25 this is of course 301 amps you need to select a 301 breaker, but I think NEC 240.6 will allow a 300 amp. ((sorry I do not have my code book and I am on the road)) </span></div><div><span>Good Luck</span></div><div><span>Darryl </span></div><div><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt;"><div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"><font size="2" face="Arial"><div style="margin: 5px 0px; padding: 0px; border: 1px solid rgb(204, 204, 204); height: 0px; line-height: 0; font-size: 0px;" class="hr"
contentEditable="false" readonly="true"></div><b><span style="font-weight: bold;">From:</span></b> Mark Frye <markf@berkeleysolar.com><br><b><span style="font-weight: bold;">To:</span></b> 'Rebekah Hren' <bekahhren@yahoo.com>; 'RE-wrenches' <re-wrenches@lists.re-wrenches.org><br><b><span style="font-weight: bold;">Sent:</span></b> Wednesday, November 16, 2011 11:43 AM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [RE-wrenches] Sizing 3 phase OCPD - main<br></font><br>
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<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"><font color="#0000ff" size="2" face="Arial">Rebekah,</font></span></div>
<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"><font color="#0000ff" size="2" face="Arial"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"><font color="#0000ff" size="2" face="Arial">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.</font></span></div>
<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"><font color="#0000ff" size="2" face="Arial"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"><font color="#0000ff" size="2" face="Arial">The second equation would be the correct
one.</font></span></div>
<div dir="ltr" align="left"><span class="yiv1192680486093484017-16112011"></span> <br><span lang="en-us"><font size="2" face="Arial">Mark Frye</font></span> <br><span lang="en-us"><font size="2" face="Arial">Berkeley Solar Electric Systems</font></span>
<br><span lang="en-us"><font size="2" face="Arial">303 Redbud Way</font>
<br><span lang="en-us"><font size="2" face="Arial">Nevada City, CA
95959</font></span></span> <br><span lang="en-us"><font size="2" face="Arial">(530)
401-8024</font></span> <br><span lang="en-us"></span><a href="http://www.berkeleysolar.com/" rel="nofollow" target="_blank"><span lang="en-us"><u><font color="#0000ff" size="2" face="Arial">www.berkeleysolar.com</font></u></span></a><span lang="en-us"><font size="2" face="Arial"> </font></span> </div>
<div> </div><br>
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<font size="2" face="Tahoma"><b>From:</b> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Rebekah
Hren<br><b>Sent:</b> Wednesday, November 16, 2011 9:36 AM<br><b>To:</b>
RE-wrenches@lists.re-wrenches.org<br><b>Subject:</b> [RE-wrenches] Sizing 3
phase OCPD - main<br></font><br></div>
<div></div>
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<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>Hi
wrenches, </span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'><br></span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>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\u2019t
apparently carry any current. </span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'></span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>Recommended
interconnection breaker is 35 Amps. Ok fine, but what should the main breaker
and main panel busbar rating be? </span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'></span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>What I\u2019m not
sure about is if this is the right equation for the main breaker in a panel
combining all ten inverter outputs: </span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>10 x
24.1A x \u221a3 x 1.25 = 521.8 A</span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'></span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>or is this the
right equation:</span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>10 x 24.1A x
1.25 = 301.25 A</span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'></span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>The busbar
rating should be easy, once I get the main disco OCPD figured out.
</span></div>
<div class="yiv1192680486MsoNormal"><span style='font-family: "Times New Roman";'>Main OCPD +
(10 x 35) \u2264 120% busbar
rating</span></div></span></div>
<div><br></div>
<div><br></div>
<div>Thanks for the help!<br>Rebekah Hren</div></div></div>
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