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<DIV dir=ltr align=left><SPAN class=984140215-30032011><FONT color=#0000ff
size=2 face=Arial>Jason,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=984140215-30032011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=984140215-30032011><FONT color=#0000ff
size=2 face=Arial>I think, going back to the diagram in the article, the feeder
breaker is rated at 80A, the feeder conductors are rated at 80A, and the
subpanel is rated at 80A, assuming that there are no loads connected in the
subpanel. Even if there were up to 100A of loads in the subpanel, you would
not exceed the allowance for the feeder or the sub-panel. Still,
if you do have loads in the subpanel, you have to up sizes the sub-panel,
but not the feeder conductor.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=984140215-30032011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><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></SPAN> <BR><SPAN lang=en-us><FONT size=2 face=Arial>Nevada
City, CA 95959</FONT></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/"><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>
<DIV dir=ltr lang=en-us class=OutlookMessageHeader align=left>
<HR tabIndex=-1>
<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>Jason
Szumlanski<BR><B>Sent:</B> Wednesday, March 30, 2011 5:18 AM<BR><B>To:</B>
RE-wrenches<BR><B>Subject:</B> Re: [RE-wrenches] sizing a sub-panel used
tocombinemultipleinverter outputs<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=WordSection1>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Another
key is to remember that this discussion also applies to the conductor between
the main panel and subpanel. In a large PV system, this could result in a pretty
large wire between the two panels, and a significant cost that is often
overlooked. In some cases it makes sense to locate the subpanel close to the
main panel and run multiple sets of smaller wires from the inverters to the
subpanel.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">And
because the calculation is based on the first OC protection connected to the
inverters, adding a main breaker (theoretically 80A in this example) in the
subpanel doesn’t change things. Even though this wire would be theoretically
protected by an 80A breaker at each end, you can’t size the wire for 160A / 1.2
= 133.3A. You have to size for 180A/1.2 = 150A. (not that it makes much of a
difference in this example, but it still must be
considered)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">At
least that’s how I understand it…<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d">Jason
Szumlanski<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Fafco
Solar</SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 4pt">
<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<DIV>
<DIV
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<P class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; COLOR: windowtext; FONT-SIZE: 10pt">From:</SPAN></B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; COLOR: windowtext; FONT-SIZE: 10pt">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B>On Behalf Of </B>Mark
Frye<BR><B>Sent:</B> Wednesday, March 30, 2011 1:33 AM<BR><B>To:</B>
'RE-wrenches'<BR><B>Subject:</B> Re: [RE-wrenches] sizing a sub-panel used to
combinemultipleinverter outputs<o:p></o:p></SPAN></P></DIV></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: blue; FONT-SIZE: 10pt">Opps!</SPAN><o:p></o:p></P>
<P class=MsoNormal> <o:p></o:p></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: blue; FONT-SIZE: 10pt">My bad,
I was thinking of a single phase system, not the three phase system
shown in the article.</SPAN><o:p></o:p></P>
<P class=MsoNormal> <o:p></o:p></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: blue; FONT-SIZE: 10pt">For the
three phase system Kent is correct in counting 180A of supply per
bar.</SPAN><o:p></o:p></P>
<P class=MsoNormal> <o:p></o:p></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Mark Frye</SPAN>
<BR><SPAN style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Berkeley
Solar Electric Systems</SPAN> <BR><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">303 Redbud Way</SPAN>
<BR><SPAN style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Nevada
City, CA 95959</SPAN> <BR><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">(530) 401-8024</SPAN>
<BR><A href="http://www.berkeleysolar.com/"><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">www.berkeleysolar.com</SPAN></A><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt"> </SPAN>
<o:p></o:p></P>
<DIV>
<P class=MsoNormal> <o:p></o:p></P></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<DIV style="TEXT-ALIGN: center" class=MsoNormal align=center>
<HR align=center SIZE=2 width="100%">
</DIV>
<P style="MARGIN-BOTTOM: 12pt" class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: 10pt">From:</SPAN></B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: 10pt">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B>On Behalf Of </B>Mark
Frye<BR><B>Sent:</B> Tuesday, March 29, 2011 10:17 PM<BR><B>To:</B>
'RE-wrenches'<BR><B>Subject:</B> Re: [RE-wrenches] sizing a sub-panel used to
combine multipleinverter outputs</SPAN><o:p></o:p></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: blue; FONT-SIZE: 10pt">I think
Kent and I agree. For the case where the subpanel is not dedicated a PV
sub-panel he is calculating for 2 - 50A breakers and I calculated for 3 - 50A
breakers.</SPAN><o:p></o:p></P>
<P class=MsoNormal><BR><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Mark Frye</SPAN>
<BR><SPAN style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Berkeley
Solar Electric Systems</SPAN> <BR><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">303 Redbud Way</SPAN>
<BR><SPAN style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">Nevada
City, CA 95959</SPAN> <BR><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">(530) 401-8024</SPAN>
<BR><A href="http://www.berkeleysolar.com/"><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt">www.berkeleysolar.com</SPAN></A><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; FONT-SIZE: 10pt"> </SPAN>
<o:p></o:p></P>
<DIV>
<P class=MsoNormal> <o:p></o:p></P></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<DIV style="TEXT-ALIGN: center" class=MsoNormal align=center>
<HR align=center SIZE=2 width="100%">
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<P style="MARGIN-BOTTOM: 12pt" class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: 10pt">From:</SPAN></B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: 10pt">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B>On Behalf Of </B>Kent
Osterberg<BR><B>Sent:</B> Tuesday, March 29, 2011 9:26 PM<BR><B>To:</B>
RE-wrenches<BR><B>Subject:</B> Re: [RE-wrenches] sizing a sub-panel used to
combine multiple inverter outputs</SPAN><o:p></o:p></P>
<P class=MsoNormal>Per 705.12(D) the sub-panel could be any distribution
equipment on the premises. So the question becomes: is the sub-panel capable of
supplying branch circuits or feeder loads? If yes, then the sum of the breakers
(potentially) feeding the bus is 180 amps so a 150-amp rating is required and
the inverters would have to feed the opposite end of the bus bars. If no, the
code is not clear on the requirement, but obviously the 80-amp breaker in the
main panel limits the maximum current flowing through the sub-panel.
<BR><BR>Kent Osterberg<BR>Blue Mountain
Solar<BR><BR><o:p></o:p></P></DIV></BODY></HTML>