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<div class="moz-cite-prefix">I agree with Jason that the panel, as
described, would be capable of supplying multiple branch circuits
and could be deemed non-compliant, but I've found inspectors here
to be reasonable about this practice. It's perfectly safe to add a
branch circuit, even multiple ones, to an ac combiner. As long as
it is for operating associated equipment such as communications
devices like the Envoy, or data loggers, or power to operate a
tracker controller and motor, it should be allowed.<br>
<br>
Consider a 100-amp panel being used as an ac combiner with four
20-amp circuit breakers being backfed with micro-inverters. A few
small loads on this panel just lowers the current on the bus bars.
The risk that the 120% rule is supposed to address is the
possibility of overloading the bus bars. In the case of the ac
combiner that could happen if someone were to add some very large
loads to it.<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
t: 541-568-4882</pre>
<br>
On 7/1/2012 6:46 AM, Jason Szumlanski wrote:<br>
</div>
<blockquote
cite="mid:CAJJtG3rvU4K1UR6zk9CYHFjoH28acoiF7KV5K1f9GXUqzfYS6w@mail.gmail.com"
type="cite">Well, if you install a bunch of 2-pole breakers for
the.inverters, and then add a single pole breaker for the Envoy,
there is definitely one space left and the panel would be
"capable" of supplying additional branch circuits.
<div>
<br>
</div>
<div>
<div>Just being devil's advocate here... I'm with you, but we
need more clarity and less room for interpretation on this
matter. </div>
<div><br clear="all">
Jason Szumlanski
<div>Fafco Solar</div>
<div>
<br>
</div>
<br>
<br>
<br>
<div class="gmail_quote">On Sat, Jun 30, 2012 at 5:09 PM, Kirk
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:kirk@vtsolar.com" target="_blank">kirk@vtsolar.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF">
<div>I would argue a single dedicated load circuit for
the Enphase Envoy, in a dedicated inverter combiner
panel, is code legal. Why? Because 705.12 states the
distribution equipment must be capable of supplying
"multiple branch circuits" for the 120% rule to apply.
A single dedicated circuit for the Envoy appears to
comply. Use a load center with a lockable cover if
there are extra slots and you have done due
diligence. <span class="HOEnZb"><font color="#888888"><br>
<br>
Kirk Herander
<div>VSE</div>
</font></span></div>
<div>
<div class="h5">
<div><br>
On Jun 27, 2012, at 11:51 AM, Jason Szumlanski
<<a moz-do-not-send="true"
href="mailto:jason@fafcosolar.com"
target="_blank">jason@fafcosolar.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>If you install a combiner panel that can
supply additional branch circuits, it becomes
part of the building distribution system. Note
that Enphase recommends you install a branch
circuit to supply power to the Envoy device
right from the combiner panel. If that is the
case, the panel is certainly part of the
building distribution system and is obviously
capable of supplying branch circuits, in which
case the 120% rule would apply. I don't like it
and I don't necessarily agree with it, but based
on my strict interpretation of the code I can
see why an AHJ would require application of this
section in this case.
<div>
<div><br clear="all">
Jason Szumlanski
<div>Fafco Solar</div>
<div><br>
</div>
<br>
<br>
<br>
<div class="gmail_quote">On Wed, Jun 27,
2012 at 10:59 AM, Chris Mason <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:cometenergysystems@gmail.com" target="_blank">cometenergysystems@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex">
I don't think this is expressed in the
code, but in my opinion, the 120%
applies to the building distribution
equipment, not to parts of the solar
system. In the case where a panel is
being used to combine multiple inverter
outputs, the panel is part of the solar
system only. The 120% rule was an
accommodation to allow solar to feed a
building distribution panel and is not
applicable to solar system components.
It would be good if the code could
indicate this more clearly.
<div>
<div><br>
<br>
<div class="gmail_quote">On Wed, Jun
27, 2012 at 8:29 AM, Jason
Szumlanski <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:jason@fafcosolar.com"
target="_blank">jason@fafcosolar.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex">
Kirk,
<div><br>
</div>
<div>That's basically what I
said. Unfortunately, your
opinion holds no weight with
my local AHJ's. I've argued
the point till blue in the
face. Although, I have never
had the instance where all
available slots were filled in
the combiner panel - I might
be able to argue that case
successfully.</div>
<span><font color="#888888">
<div><br>
</div>
</font></span>
<div><span><font color="#888888">Jason
Szumlanski
<div>Fafco Solar</div>
<div><br>
</div>
<br>
<br>
<br>
</font></span>
<div class="gmail_quote">
<div>
<div>On Tue, Jun 26, 2012
at 4:53 PM, Kirk
Herander <span
dir="ltr"><<a
moz-do-not-send="true"
href="mailto:kirk@vtsolar.com" target="_blank">kirk@vtsolar.com</a>></span>
wrote:<br>
</div>
</div>
<blockquote
class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div>
<div>
<div link="blue"
vlink="purple"
lang="EN-US">
<div>
<p
class="MsoNormal"><span
style="color:#1f497d">Jason,</span></p>
<p
class="MsoNormal"><span
style="color:#1f497d"> </span></p>
<p
class="MsoNormal">
<span
style="color:#1f497d">In
your email
below you
state:</span></p>
<p
class="MsoNormal"><span
style="color:#1f497d"> </span></p>
<p
class="MsoNormal"><span
style="color:#1f497d">“</span>You DO need to observe the 120% rule for
the combining
subpanel,
regardless of
whether there
are loads
present, at
least in
jurisdictions
where I have
worked. I've
heard that some
inspectors will
allow you to
ignore it if it
is labeled as a
PV combiner with
"add no loads"
notation.<span
style="color:#1f497d">”</span></p>
<p
class="MsoNormal"><span
style="color:#1f497d"> </span></p>
<p
class="MsoNormal"><span
style="color:#1f497d">NEC 705.12 (D) states that the distribution
equipment (in
this case the
combiner
panel, fed by
multiple
inverters and
a utility
source) must
be “capable of
supplying
multiple
branch
circuits or
feeders or
both” for
(D)(1) through
(7) to apply.
If you fully
populated a
combiner panel
with inverter
breakers,
leaving no
slots for load
breakers, it
is not capable
of supplying
branch
circuits or
feeders, and
IMO the 120%
rule does not
apply to the
combiner buss
or the
conductors
back to its
point of
utility
interconnect.
I have argued
this point as
well as label
combiners
“load circuits
prohibited”
(with or
without
available
slots) and
received AHJ
approval.</span></p>
<p
class="MsoNormal"><span
style="color:#1f497d"> </span></p>
<p
class="MsoNormal"><span
style="color:#1f497d">You could also just lock shut a combiner that had
spare slots as
a deterrent to
adding load
breakers.</span></p>
<p
class="MsoNormal"><span
style="color:#1f497d"> </span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Kirk
Herander</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">VT
Solar, LLC</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">dba
Vermont Solar
Engineering</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">NABCEP<sup>TM
</sup>Certified
installer
Charter Member</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">NYSERDA-eligible
Installer</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d">VT
RE Incentive
Program
Partner</span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><a
moz-do-not-send="true" href="tel:802.863.1202" value="+18028631202"
target="_blank">802.863.1202</a></span><span
style="font-size:18.0pt;font-family:"Calibri","sans-serif";color:#1f497d"></span></p>
<p
class="MsoNormal"><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p
class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a
moz-do-not-send="true"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a
moz-do-not-send="true"
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>
Tuesday, June
26, 2012 8:28
AM<br>
<b>To:</b>
RE-wrenches<br>
<b>Subject:</b>
Re:
[RE-wrenches]
Enphase grid
tie question</span></p>
<p
class="MsoNormal"> </p>
<p
class="MsoNormal">I'll
email you
off-list a
1-line diagram
from a system
with 164
microinverters
broken down into
8 strings in a
208V system.
This particular
system used two
subpanels to
accumulate PV,
but that was
only because we
had to backfeed
two existing
subpanels due to
the size of
existing
480/208V
transformers.
You will have to
look at the
utility service
and all existing
equipment.</p>
<div>
<p
class="MsoNormal"> </p>
</div>
<div>
<p
class="MsoNormal">Regarding
the breakers
in the
subpanel, you
will only need
a maximum of a
20A breaker
for each
string. The
max inverters
per string is
25 and the
calculation
for OCPD is:</p>
</div>
<div>
<p
class="MsoNormal"> </p>
</div>
<div>
<p
class="MsoNormal">215W
/ 208V x 25
inverters /
1.732 x 1.25 =
18.65A</p>
</div>
<div>
<p
class="MsoNormal"> </p>
</div>
<div>
<p
class="MsoNormal">
<span
style="color:#1f497d">“</span>You
DO need to
observe the
120% rule for
the combining
subpanel,
regardless of
whether there
are loads
present, at
least in
jurisdictions
where I have
worked. I've
heard that
some
inspectors
will allow you
to ignore it
if it is
labeled as a
PV combiner
with "add no
loads"
notation.<span
style="color:#1f497d">”</span></p>
</div>
<div>
<p
class="MsoNormal"> </p>
</div>
<div>
<p
class="MsoNormal">Use
a MLO panel
with a fusible
disconnect
between the
subpanel and
the
interconnection
point. If you
use a 225A
panel, you can
feed it with
270A. With
eight 20A
backfed PV
circuits, you
would need to
protect the
line side of
the panel with
a 100A fusible
disconnect.
That probably
isn't going to
work. You may
be best off
from a cost
perspective
using two 225A
subpanels and
two 60A
fusible
disconnects.
Anything
larger than a
60A 3P
disconnect and
the price
skyrockets. It
all depends on
your circuit
calculations
and the
existing
equipment. Of
course, you
would need two
spaces for
your
interconnection
point.</p>
</div>
<div>
<div>
<div>
<p
class="MsoNormal"> </p>
</div>
<div>
<p
class="MsoNormal">Jason
Szumlanski</p>
<div>
<p
class="MsoNormal">Fafco
Solar</p>
</div>
</div>
</div>
<p
class="MsoNormal"
style="margin-bottom:12.0pt">
<br>
</p>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
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</blockquote>
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</blockquote>
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</blockquote>
</div>
</div>
</div>
</blockquote>
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