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<p>I researched some articles on this before replying but they are
too out of date to be of much help. <br>
</p>
<p>This is my two cents worth.</p>
<p>The pv system EGC needs to be connected to the grounding busbar
system. <br>
</p>
<p>The pv system EGC also needs to be irreversibly connected to the
GEC.</p>
<p>The system neutral and the ECG need to be bonded, usually that is
at the Supply Side Disconnect.</p>
<p>If you have a ac combiner upstream, it should just be grounded,
not bonded. If a production meter is involved, that too, should be
grounded, not bonded. Below is a graphic from Mike Holt with some
edits. Chris<br>
</p>
<p><img src="cid:part1.B4321730.FAC784A5@entech-engineering.com"
alt=""></p>
<p><br>
</p>
<div class="moz-cite-prefix">On 9/7/2019 11:55 AM, Ray wrote:<br>
</div>
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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>
<div>
<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
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<div>
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<div dir="ltr">
<div dir="ltr">
<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>
</div>
</div>
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