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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hello wrenchers<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>We’ve got 2 systems [23kW and 44kW] going up on Solarmount
onto a single large custom steel dunnage structure on top of a warehouse.
<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>From the ground it will look like a single massive array, but
actually <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>1/3 of the modules (8 strings) will be fed into (2) Fronius
[which will feed one bldg service, with its own water main ground], and <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>2/3 of the modules (16 strings) will be fed into (4) Fronius [which
will feed a different bldg service, with its own water main ground.]<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>All of the mods will be weebed onto rails, which will be
mechanically connected to the I-beams, which is welded to the building steel,
which goes into the ground.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>We plan to land all of the DC equipment grounds onto a common
bus bar near the inverter bank; from that we plan to run a bare solid #6 copper
to each inverter.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>We’ll run #6 GEC’s out of each inverter, to be
irreversibly crimped onto a dedicated single #4 GEC for each building, which
will land on their respective water mains.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The question is: does this mean </span><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>we're also bonding two
neutrals together, which means current could flow into the service at Building
A, through a lightbulb, back to their neutral buss, up our EGC/GEC, down to
Building B's neutral buss, and out through their service neutral? That may
pose two issues:<br>
<br>
1) If Building A has a 400A service and Building B has a 100A service, building
B's neutral is now in major danger of an overcurrent situation. (There are
probably other potential problems as well, if the two services are out of phase
for example)<br>
2) The bonded GEC now becomes a grounded current-carrying conductor<br>
<br>
This example seems pretty unique; we haven't found anything in the code yet
that specifically addresses the situation, but 250.32 prohibits something
similar on the grounds that it causes point #2 as above. A possible
counter-argument to point #1 : does potential exist between L1/2/3 of
transformer A and the neutral of transformer B?</span><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> </span><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>Fun stuff..cheers for reading
this<o:p></o:p></span></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;
font-family:"Calibri","sans-serif";color:#1F497D'>Jim Mac<o:p></o:p></span></p>
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