<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Per your question:<br><br><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">> 1 - What does a UL1741 inverter do when it is connected<br>> to a
line that is experiencing a short-circuit or ground fault?<br></font></span><br>Presuming a hard short, the voltage in that circuit would be essentially zero, and a UL1741 compliant inverter would cease producing power in less than 0.1 second.<br><br><br>Dan<br>Sr. Engineer<br>Exeltech<br><br><br><br><br><br><br><br><br>--- On <b>Wed, 3/30/11, Mark Frye <i><markf@berkeleysolar.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: Mark Frye <markf@berkeleysolar.com><br>Subject: Re: [RE-wrenches] sizing a sub-panel used tocombine multipleinverter outputs<br>To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org><br>Date: Wednesday, March 30, 2011, 12:37 PM<br><br><div id="yiv1283215088">
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<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">That is a really good question Brian.</font></span></div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">Mostly when thinking about these sizing issues I think about
overload conditions and not so much about short-circuit and ground fault
conditions.</font></span></div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">So two questions come up:</font></span></div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">1 - What does a UL1741 inverter do when it is connected to a
line that is experiencing a short-circuit or ground fault?</font></span></div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">2 - What does the feeder breaker do when it is connected to a
line that is experiencing a short-circuit or ground fault?</font></span></div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="yiv1283215088828221817-30032011"><font color="#0000ff" face="Arial" size="2">As far as number two, thanks to all the great work we do
establishing low impedence fault paths back to circuirt protectors, the breaker
is going to trip at it's rating and protect the wire at the same
rating. But that doesn't mean that the conductor won't see more
than rated amps during the fault. It will see alot more than for a
very short time. During this very short time frame, the actual currents flowing
into the fault from the utility side of the equation far far exceed the currents
contributed by the power limited inverter side.</font></span></div>
<div> <br><span lang="en-us"><font face="Arial" size="2">Mark Frye</font></span>
<br><span lang="en-us"><font face="Arial" size="2">Berkeley Solar Electric
Systems</font></span> <br><span lang="en-us"><font face="Arial" size="2">303 Redbud
Way</font></span> <br><span lang="en-us"><font face="Arial" size="2">Nevada
City, CA 95959</font></span> <br><span lang="en-us"><font face="Arial" size="2">(530) 401-8024</font></span> <br><span lang="en-us"></span><a rel="nofollow" target="_blank" href="http://www.berkeleysolar.com/"><span lang="en-us"><u><font color="#0000ff" face="Arial" size="2">www.berkeleysolar.com</font></u></span></a><span lang="en-us"><font face="Arial" size="2"> </font></span> </div>
<div> </div><br>
<div dir="ltr" class="yiv1283215088OutlookMessageHeader" align="left" lang="en-us">
<hr tabindex="-1">
<font face="Tahoma" size="2"><b>From:</b> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Brian
Teitelbaum<br><b>Sent:</b> Wednesday, March 30, 2011 10:02 AM<br><b>To:</b>
RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] sizing a sub-panel used
tocombine multipleinverter outputs<br></font><br></div>
<div></div>
<div class="yiv1283215088WordSection1">
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">Wouldn’t
a fault in that conductor between the main and the sub have a potential for up
to 160A of current? I would think that at noon on a sunny day, the inverter
system could produce 80A from one direction (albeit really only the max amperage
outputs of the inverters) and 80A of grid current from the main into a partial
fault.</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">Brian
Teitelbaum</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">AEE
Solar </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<div>
<div style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;">
<p class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">From:</span></b><span style="font-family: '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 9:49 AM<br><b>To:</b>
'RE-wrenches'<br><b>Subject:</b> Re: [RE-wrenches] sizing a sub-panel used to
combine multipleinverter outputs</span></p></div></div>
<p class="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: blue; font-size: 10pt;">Al,</span><span style="color: windowtext;"></span></p>
<p class="yiv1283215088MsoNormal"><span style="color: windowtext;"> </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: blue; font-size: 10pt;">I would
say that yes the meter is a load and this goes to show the relative inadequacy
of the vocabulary we are using in the discussion. In the example we have been
using with the 80A breaker, wire and sub panel, you could have up to 80A of
loads installed in the sub and still not create an over current condition in any
of that equipment.</span><span style="color: windowtext;"></span></p>
<p class="yiv1283215088MsoNormal"><span style="color: windowtext;"><br></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">Mark
Frye</span><span style="color: windowtext;"> <br></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">Berkeley
Solar Electric Systems</span><span style="color: windowtext;"> <br></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">303
Redbud Way</span><span style="color: windowtext;"> <br></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">Nevada
City, CA 95959</span><span style="color: windowtext;"> <br></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">(530)
401-8024</span><span style="color: windowtext;"> <br><a rel="nofollow" target="_blank" href="http://www.berkeleysolar.com/"><span style="font-family: 'sans-serif'; font-size: 10pt;">www.berkeleysolar.com</span></a></span><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;"> </span><span style="color: windowtext;"> </span></p>
<div>
<p class="yiv1283215088MsoNormal"><span style="color: windowtext;"> </span></p></div>
<p class="yiv1283215088MsoNormal"><span style="color: windowtext;"> </span></p>
<div style="text-align: center;" class="yiv1283215088MsoNormal" align="center"><span style="color: windowtext;">
<hr align="center" size="2" width="100%">
</span></div>
<p style="margin-bottom: 12pt;" class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">From:</span></b><span style="font-family: '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>Al
Frishman<br><b>Sent:</b> Wednesday, March 30, 2011 9:00 AM<br><b>To:</b>
'RE-wrenches'<br><b>Subject:</b> Re: [RE-wrenches] sizing a sub-panel used to
combine multipleinverter outputs</span><span style="color: windowtext;"></span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">Is
a monitoring system installed in the Load Center to measure the cumulative kWh’s
of the inverter’s considered a load? </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">The
type of monitoring device I am talking about has CT’s that go around the
conductors and the Voltage ref is taken by attaching conductors to each phase,
the Neutral and the ground bar. The digital Meter has a 3-pole
5A breaker in it so the conductors in the load center can be connected to lugs
on the bus bar directly.</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<div>
<p class="yiv1283215088MsoNormal"><i><span style="font-family: 'sans-serif'; font-size: 10.5pt;">Al
Frishman</span></i><span style="font-family: 'sans-serif'; font-size: 13.5pt;"><br></span><span style="">Aeon</span><span style="">Solar</span><span style="font-family: 'sans-serif'; font-size: 13.5pt;"></span></p>
<p class="yiv1283215088MsoNormal"><i><span style="font-family: 'sans-serif'; font-size: 10.5pt;">(917) 699-6641
- cell</span></i><span style="font-family: 'sans-serif'; font-size: 10.5pt;"><br><i>(888)
460-2867</i><br><i><a rel="nofollow" target="_blank" href="http://www.aeonsolar.com/">www.aeonsolar.com</a></i></span><span style="font-family: 'sans-serif'; font-size: 13.5pt;"></span></p>
<p style="text-align: center;" class="yiv1283215088MsoNormal" align="center"><i><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 14pt;"> </span></i></p></div>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<div>
<div style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;">
<p class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">From:</span></b><span style="font-family: '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>Jason
Szumlanski<br><b>Sent:</b> Wednesday, March 30, 2011 8:18 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="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); 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="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); 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="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">At
least that’s how I understand it…</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<div>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125);">Jason
Szumlanski</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;">Fafco
Solar</span><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 4pt;">
</span></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p></div>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: rgb(31, 73, 125); font-size: 11pt;"> </span></p>
<div>
<div style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;">
<p class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; color: windowtext; font-size: 10pt;">From:</span></b><span style="font-family: '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</span></p></div></div>
<p class="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: blue; font-size: 10pt;">Opps!</span></p>
<p class="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: '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></p>
<p class="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; color: blue; font-size: 10pt;">For the
three phase system Kent is correct in counting 180A of supply per
bar.</span></p>
<p class="yiv1283215088MsoNormal"> </p>
<p class="yiv1283215088MsoNormal"><span style="font-family: 'sans-serif'; font-size: 10pt;">Mark Frye</span>
<br><span style="font-family: 'sans-serif'; font-size: 10pt;">Berkeley
Solar Electric Systems</span> <br><span style="font-family: 'sans-serif'; font-size: 10pt;">303 Redbud Way</span>
<br><span style="font-family: 'sans-serif'; font-size: 10pt;">Nevada
City, CA 95959</span> <br><span style="font-family: 'sans-serif'; font-size: 10pt;">(530) 401-8024</span>
<br><a rel="nofollow" target="_blank" href="http://www.berkeleysolar.com/"><span style="font-family: 'sans-serif'; font-size: 10pt;">www.berkeleysolar.com</span></a><span style="font-family: 'sans-serif'; font-size: 10pt;"> </span>
</p>
<div>
<p class="yiv1283215088MsoNormal"> </p></div>
<p class="yiv1283215088MsoNormal"> </p>
<div style="text-align: center;" class="yiv1283215088MsoNormal" align="center">
<hr align="center" size="2" width="100%">
</div>
<p style="margin-bottom: 12pt;" class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; font-size: 10pt;">From:</span></b><span style="font-family: '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></p>
<p class="yiv1283215088MsoNormal"><span style="font-family: '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></p>
<p class="yiv1283215088MsoNormal"><br><span style="font-family: 'sans-serif'; font-size: 10pt;">Mark Frye</span>
<br><span style="font-family: 'sans-serif'; font-size: 10pt;">Berkeley
Solar Electric Systems</span> <br><span style="font-family: 'sans-serif'; font-size: 10pt;">303 Redbud Way</span>
<br><span style="font-family: 'sans-serif'; font-size: 10pt;">Nevada
City, CA 95959</span> <br><span style="font-family: 'sans-serif'; font-size: 10pt;">(530) 401-8024</span>
<br><a rel="nofollow" target="_blank" href="http://www.berkeleysolar.com/"><span style="font-family: 'sans-serif'; font-size: 10pt;">www.berkeleysolar.com</span></a><span style="font-family: 'sans-serif'; font-size: 10pt;"> </span>
</p>
<div>
<p class="yiv1283215088MsoNormal"> </p></div>
<p class="yiv1283215088MsoNormal"> </p>
<div style="text-align: center;" class="yiv1283215088MsoNormal" align="center">
<hr align="center" size="2" width="100%">
</div>
<p style="margin-bottom: 12pt;" class="yiv1283215088MsoNormal"><b><span style="font-family: 'sans-serif'; font-size: 10pt;">From:</span></b><span style="font-family: '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></p>
<p style="margin-bottom: 12pt;" class="yiv1283215088MsoNormal">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</p></div></div><br>-----Inline Attachment Follows-----<br><br><div class="plainMail">_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address: <a ymailto="mailto:RE-wrenches@lists.re-wrenches.org" href="/mc/compose?to=RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br><br>Options & settings:<br><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" target="_blank">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive: <a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" target="_blank">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out participant bios:<br>www.members.re-wrenches.org<br><br></div></blockquote></td></tr></table><br>