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<p>I've seen all 3 options. This question actually comes up in the
wiring of sub panels, and out buildings as well. I find
improperly bonded wiring all the time that allows current to flow
on the ground, because Neutral was bonded at both ends, with an
EGC also run in parallel(option 2 done incorrectly). This is a
big No No, and can cause voltages on exposed metal. Next, my
understanding is that option 1 is no longer allowed on a single
service, although that is how all grid connected houses are wired
to the grid and each other with separate meters. (sorry I'm out
of the office, so I don't have a code reference)<br>
</p>
<p>As far as different opinions from different AHJs, I've had
inspectors switch mid project, with the first inspector saying
option 2 was ok, then the 2nd inspector required us to later run a
GEC back to the GE after. On option 3, you would always want an
EGC running with the conductors. I have occasionally then not
connected that EGC at one end, if we also had the separate GEC
running back to the GE, to avoid a "lightning loop". Having 2
ground conductors running to the same point along different paths
allows lightning to induce a current in the wiring through the
loop that is created. </p>
<p>It really does get more complicated, when you also consider the
grounding system's secondary purpose of providing lightning
protection. I have a great book from Polyphasor on grounding for
lightning protection that is a whole nother world beyond NEC.
They had grounding systems with dozens of GEs (for communications
towers) but everything was attached in a star pattern to avoid any
lightning loops. Its actually possible to meet both NEC and
lightning protection requirements, but it takes more
consideration, and hence the varied opinions. Not having current
running on the ground system however is a serious safety issue.<br>
</p>
<pre class="moz-signature" cols="72">Ray Walters
Remote Solar
303 505-8760</pre>
<div class="moz-cite-prefix">On 9/7/19 7:05 AM, Jason Szumlanski
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAE438R9mxVV2x-PEJM-=8xi_cKOZpP-1g7zKt2kto4CL4mtKkw@mail.gmail.com">
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">There doesn't
seem to be a definitive and detailed consensus
article/resource out there that addresses this topic. There
are articles that dance around the subject, but little in
terms of practical ways to accomplish grounding/binding with a
supply side interconnection. AHJ's and engineers have all
kinds of differing opinions. As an industry, it seems like we
should have a definitive guide on the subject.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Let's take a
simple/common ungrounded inverter (or microinverter) system
that is interconnected using supply side taps inside an
existing load center with main disconnect. From the roof to
the PV AC Combiner you have an appropriately sized EGC, and no
GEC because a GEC is not required in this ungrounded system
other than the existing premises GEC (and GE system). Let's
assume the AHJ agrees that no GEC is required from the roof,
which is a whole other subject that drive me nuts). Coming
from the PV AC Combiner panel (if present) or Inverter you
have two current carrying conductors L1 and L2 that are tapped
on the service conductors. The neutral from the PV AC Combiner
or inverter is landed on the existing neutral bus of the same
main load center where the tap is made. </div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Now what
happens with the EGC that comes from the roof to the PV AC
Combiner (or inverter)?</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">What I have run
into, and there may be other opinions, are the following
assertions by AHJs:</div>
<div class="gmail_default">
<ul>
<li><font face="arial, helvetica, sans-serif">Land the EGC
on the PV AC Combiner and stop there. Bond neutral to
ground. The neutral carries the fault current to the
system bonding point in the main service panel.</font></li>
<li><font face="arial, helvetica, sans-serif">Land the EGC
in the PV AC Combiner and continue the EGC to the ground
bar in the main service panel. Do not bond neutral to
ground in the PC AC Combiner.</font></li>
<li><font face="arial, helvetica, sans-serif">From the PV AC
Combiner, install a GEC directly to the existing
grounding electrode, and do not run an EGC to the main
service panel.</font></li>
<li><font face="arial, helvetica, sans-serif">Some
combination of the above.</font></li>
</ul>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Can anyone
point to a clear and concise 3-line diagram that explains the
acceptable options? Hopefully something that and AHJ will
consider, like an IAEI article or NEC Handbook graphic.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
</div>
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data-smartmail="gmail_signature">
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<div>
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<div style="text-align:start"><font
face="arial, helvetica, sans-serif">J<span
class="gmail_default"
style="font-family:arial,helvetica,sans-serif">ason
Szumlanski</span></font></div>
<div style="text-align:start"><font
face="arial, helvetica, sans-serif"><span
class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Florida
Solar Desing Group</span></font></div>
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