It seems to me that the conductor should not be subject to the 120% rule despite what the code says. The potential safety issue here is overloading the neutral bus, right? While feeding currents could be additive in the panel, they would be subtractive on the feeder, no? I seem to remember seeing this discussion on the list before. <br>
<br>Kris <br><br><div class="gmail_quote">On Fri, Sep 28, 2012 at 8:26 AM, Aaron Mandelkorn <span dir="ltr"><<a href="mailto:reosolar@gmail.com" target="_blank">reosolar@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">I agree. With a 150A bus being fed by 100A from the grid leaves 80 additional amps (120% of 150A) to feed the bus from outside sources. It seems to me that 40A of PV being back fed will be just fine. <div>
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</div></font></span><div><div class="h5">
<br><div><div>On Sep 28, 2012, at 6:32 AM, Drake wrote:</div><br><blockquote type="cite">
<div>
Are you sure you can't? Since the bus has a rating of 150 A and is
protected by a 100 A breaker, there is plenty of room to not over amp the
bus from the two sources of power.<br><br>
The amperage from the inverter will cancel amperage coming from the
utility in the feeder. The wire will never supply over the 100
A. The theoretical max the inverter could backfeed would be 40 Amps
in the 100 Amp cable if no loads were being supplied. It would
certainly not be a safety issue. Am I missing something in the
code?<br><br>
<br>
At 12:51 AM 9/28/2012, you wrote:<br>
<blockquote type="cite">Mac:<br><br>
Nope.<br><br>
<br>
William Miller<br><br>
PS: It's pretty straight forwards, the code says "bus or
conductor."<br><br>
wm<br><br>
PPS:<br><br>
Can you customer live with a smaller feeder breaker, say 125
amps? If so, your gold.<br><br>
wm<br><br>
<br><br>
At 06:43 PM 9/27/2012, you wrote:<br>
<blockquote type="cite">Hello wrenches,<br><br>
I am looking for advice on how the 120% rule applies to feeders for a
subpanel. I have this scenario:<br>
150A bus rating on subpanel with main breaker of 100A. The
conductors feeding this subpanel are 100A rated conductors. Can I
backfeed with a 40A breaker?<br><br>
Thanks<br><br>
-- <br><br>
<font color="#305A78"><br>
</font><br>
Mac Lewis<br><br>
<font face="Verdana"><b>"Yo solo sé que no sé nada."
-Sócrates<br>
</b></font><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Shine On!<br><br>Kris Schmid<br>Legacy Solar, LLC<br>864 Clam Falls Trail<br>Frederic, WI 54837<br><a href="http://www.legacysolar.com/" target="_blank">www.legacysolar.com</a><br>
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