To echo the wording in Kent's response, John Wiles has always advised that it doesn't matter if there are currently loads connected to the panel/conductors; if the panel/conductors are capable of having additional loads connected to it, you need to apply 609.64(B)(2). I have had luck with AHJ approval by adding signage indicating that no loads can be added to this panel/fpr combining PV inverter output only, and in one case installed a panelboard dead-front that limited the number of breakers to six (for our six combining inverters). <div>
<br></div><div>If you are installing breaker for a meter, it sounds like the panel is capable of having additional loads connected to it.</div><div><br></div><div>For discussion on code specific combiner panel requirements, or the lack thereof, I'll quote from this list last year (response is from Bill Brooks):<br>
<div><br></div><div><span class="Apple-style-span" style="border-collapse: collapse; font-family: arial, sans-serif; font-size: 13px; "><pre style="white-space: pre-wrap; ">**************</pre><pre style="white-space: pre-wrap; ">
Sent: Tuesday, January 12, 2010 10:57 AM</pre><pre style="white-space: pre-wrap; ">To: RE-wrenches</pre><pre style="white-space: pre-wrap; ">Subject: [RE-wrenches] Solar accumulation panel</pre><pre style="white-space: pre-wrap; ">
*******************</pre><pre style="white-space: pre-wrap; ">Team wrenches - I feel like I've seen a provision in the Code for installing a sub-panel to aggregate PV inverter outputs for the purpose of simplifying the actual grid connection (such as for a line-side tap) but I can't find it in 690. I also seem to remember specific verbiage that needs to be on the panel along the lines of "PV circuits only. Do not add load breakers." to ensure compliance with <span class="il" style="background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: rgb(255, 255, 136); color: rgb(34, 34, 34); background-position: initial initial; background-repeat: initial initial; ">690.64</span>(B). Does anyone know where I can find this info in the NEC? </pre>
<pre style="white-space: pre-wrap; ">Andrew Truitt</pre><pre style="white-space: pre-wrap; ">Standard Solar Inc.</pre><pre style="white-space: pre-wrap; ">********************</pre><pre style="white-space: pre-wrap; ">Response:</pre>
<pre style="white-space: pre-wrap; "> It does not exist. We tried like crazy to get it into the 2011 NEC, but to no avail. At the last second the proposal was put on hold until the 2014 NEC. Major bummer. For now it can only be done with AHJ approval. Many allow it but it is not in the NEC. Alternatively you must use the sum of supply breakers no greater than 120%. Much more restrictive.</pre>
<pre style="white-space: pre-wrap; ">Bill.</pre><p class="MsoNormal" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">********************</p></span><div><br></div>-Phil</div><div><br></div>
<div><br></div><div><br><div class="gmail_quote">On Wed, Mar 30, 2011 at 8:36 AM, Mark Frye <span dir="ltr"><<a href="mailto:markf@berkeleysolar.com">markf@berkeleysolar.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div lang="EN-US" link="blue" bgcolor="white" vlink="purple">
<div dir="ltr" align="left"><span><font color="#0000ff" size="2" face="Arial">Jason,</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" size="2" face="Arial"></font></span> </div>
<div dir="ltr" align="left"><span><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 class="im">
<div dir="ltr" align="left"><span><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"><a href="tel:%28530%29%20401-8024" target="_blank">(530) 401-8024</a></font></span> <br><span lang="en-us"></span><a href="http://www.berkeleysolar.com/" 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>
</div><div dir="ltr" lang="en-us" align="left">
<hr>
<font size="2" face="Tahoma"><b>From:</b> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Jason
Szumlanski<br><b>Sent:</b> Wednesday, March 30, 2011 5:18 AM<div><div></div><div class="h5"><br><b>To:</b>
RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] sizing a sub-panel used
tocombinemultipleinverter outputs<br></div></div></font><br></div><div><div></div><div class="h5">
<div></div>
<div>
<p class="MsoNormal"><span style="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.</span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="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)</span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt">At
least that’s how I understand it…</span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt"> </span></p>
<div>
<p class="MsoNormal"><span style="color:#1f497d">Jason
Szumlanski</span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt">Fafco
Solar</span><span style="color:#1f497d;font-size:4pt">
</span></p>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt"> </span></p></div>
<p class="MsoNormal"><span style="color:#1f497d;font-size:11pt"> </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="color:windowtext;font-size:10pt">From:</span></b><span style="color:windowtext;font-size:10pt">
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <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</span></p></div></div>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="color:blue;font-size:10pt">Opps!</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="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></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="color:blue;font-size:10pt">For the
three phase system Kent is correct in counting 180A of supply per
bar.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span style="font-size:10pt">Mark Frye</span>
<br><span style="font-size:10pt">Berkeley
Solar Electric Systems</span> <br><span style="font-size:10pt">303 Redbud Way</span>
<br><span style="font-size:10pt">Nevada
City, CA 95959</span> <br><span style="font-size:10pt"><a href="tel:%28530%29%20401-8024" target="_blank">(530) 401-8024</a></span>
<br><a href="http://www.berkeleysolar.com/" target="_blank"><span style="font-size:10pt">www.berkeleysolar.com</span></a><span style="font-size:10pt"> </span>
</p>
<div>
<p class="MsoNormal"> </p></div>
<p class="MsoNormal"> </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-size:10pt">From:</span></b><span style="font-size:10pt">
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <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></p>
<p class="MsoNormal"><span style="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></p>
<p class="MsoNormal"><br><span style="font-size:10pt">Mark Frye</span>
<br><span style="font-size:10pt">Berkeley
Solar Electric Systems</span> <br><span style="font-size:10pt">303 Redbud Way</span>
<br><span style="font-size:10pt">Nevada
City, CA 95959</span> <br><span style="font-size:10pt"><a href="tel:%28530%29%20401-8024" target="_blank">(530) 401-8024</a></span>
<br><a href="http://www.berkeleysolar.com/" target="_blank"><span style="font-size:10pt">www.berkeleysolar.com</span></a><span style="font-size:10pt"> </span>
</p>
<div>
<p class="MsoNormal"> </p></div>
<p class="MsoNormal"> </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-size:10pt">From:</span></b><span style="font-size:10pt">
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>] <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></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></p></div></div></div></div>
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