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<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial>Jason:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial>SB 5000 = 21A @ 240V, 21A x 1.25 = 26.3A needs 30A
breaker</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial>M215 = 0.9 A @ 240V, 0.9A x 9 = 8.1 A, 8.1 x 1.25 = 10.1A
needs 15A breaker. (Or that rounded to 10A and use a 10A
breaker)?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial>26.3A + 10.1A = 36.4 A needs 40A breaker</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=843081120-29092011><FONT color=#0000ff
size=2 face=Arial>So, get a new 100A main lug subpanel. Connect it to a 40A
breaker in the existing main panel. Move the existing 30A breaker into the new
subpanel and install the new 15A breaker into the same.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><FONT color=#0000ff size=2 face=Arial></FONT><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></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> Thursday, September 29, 2011 12:55 PM<BR><B>To:</B>
RE-wrenches<BR><B>Subject:</B> Re: [RE-wrenches] Adding on to existing PV
System<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV class=WordSection1>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">That’s not a bad idea, except
that 690.64(B)(2) requires that the breaker directly connected to each
inverter(s) must be used for the calculation.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">I have an existing SB5000 with a
30A breaker and a new string of nine Enphase M215’s requiring a 15A breaker. If
you combine these in a 100A or higher rated subpanel with a 40A main breaker,
you still calculate the total current supplying the busbar in the main
distribution panel based on 200A + 30A + 15A = 245A (with 30A and 15A being the
overcurrent protection directly connected to the inverters). This exceeds the
120% rule by 5A. It also requires that the ampacity of the conductors between
the two panels be 85A / 1.2 = 70.83A (assuming a 40A backfeed breaker in the
main distribution panel). If your interpretation is different, please let me
know!<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">If my interpretation is correct,
I like the idea of just adding a fusible disconnect and using #10 conductors all
the way to the tap. That would be the most cost effective solution I believe,
and since there is no foreseeable further system rating increases, the advantage
of a subpanel is reduced.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">Thanks for all the other
suggestions provided. Unfortunately I can’t put in smaller main breaker, and the
busbar in the main panel is definitely rated 200A.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<DIV>
<P class=MsoNormal><SPAN style="COLOR: #1f497d; FONT-SIZE: 12pt">Jason
Szumlanski<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">Fafco Solar</SPAN><SPAN
style="COLOR: #1f497d"><o:p></o:p></SPAN></P></DIV>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<DIV>
<DIV
style="BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt">
<P 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>Glenn
Burt<BR><B>Sent:</B> Thursday, September 29, 2011 2:40 PM<BR><B>To:</B>
'RE-wrenches'<BR><B>Subject:</B> Re: [RE-wrenches] Adding on to existing PV
System<o:p></o:p></SPAN></P></DIV></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">How about feeding both systems
into an AC combining subpanel before feeding the main load
center?<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">Often the calculations required
will allow you to do more backfeeding than the simple backfeeding a load center
with individual breakers.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d">-Glenn<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<DIV>
<DIV
style="BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt">
<P 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>Jason
Szumlanski<BR><B>Sent:</B> Thursday, September 29, 2011 11:49 AM<BR><B>To:</B>
RE-wrenches<BR><B>Subject:</B> [RE-wrenches] Adding on to existing PV
System<o:p></o:p></SPAN></P></DIV></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>We’ve been contracted to add on to an existing PV system in a
residence. The existing system has a 30A 2P Breaker on a 200A rated panel with a
200A main breaker. The new system would require a 15A breaker, which would
exceed the limit in NEC 690.64(B)(2).<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>The existing system has a fusible AC disconnect mounted next
to the meter. This was originally intended as the utility external disconnect.
The utility no longer requires a disconnect, but if we do a supply side
connection, we would need a fusible AC disconnect anyway for the new system. I
would collocate the new disconnect with the old.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Does anyone see any problem with doing a supply size
connection for the new system? Any labeling snags that I might need to
consider?<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><SPAN style="FONT-SIZE: 12pt">Jason
Szumlanski<o:p></o:p></SPAN></P>
<P class=MsoNormal>Fafco Solar<o:p></o:p></P></DIV></BODY></HTML>