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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Wrenches,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I have GEC sizing issue and would greatly appreciate any
advice you can share.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We have a small commercial grid-tie system installing on a
facility with a 4000A, 240V, 3Ph service that uses the water main as the Ground
Electrode. My engineer is referencing NEC Table 250.66 (and the 4000A
service entrance cables) to size the GEC from the inverters to the GE, and
therefore is requiring a 3/0 (maximum size required by this table).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Since this is actually a DC GEC, I think it should be sized according
to NEC 690.47(B) which references 250.166. Since the GE is a water main it
seems that 250.166(B) would apply, requiring the GEC “<i><span
style='font-style:italic'>shall not be smaller than the largest conductor
supplied by the system.” </span></i>If taken literally, the largest
conductor supplied by the system could be the 4000A service entrance cables,
which would require a GEC even larger than the seemingly excessive 3/0. For
obvious reasons I hesitate to mention this to my engineer, but I in the end I
want to do what is best.<o:p></o:p></span></font></p>
<p class=MsoNormal><i><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial;font-style:italic'><o:p> </o:p></span></font></i></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>My questions:<o:p></o:p></span></font></p>
<p class=MsoNormal><i><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial;font-style:italic'><o:p> </o:p></span></font></i></p>
<p class=MsoNormal style='text-indent:.25in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>1. Is my engineer
correct, and we should size the GEC according to 250.66? <o:p></o:p></span></font></p>
<p class=MsoNormal style='text-indent:.25in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='text-indent:.25in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>2. If #1 is no,
and 250.166(B) does apply, is “the largest conductor supplied by this
system” the 4000A service entrance cables, and the GEC size should match
these?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<ol style='margin-top:0in' start=3 type=1>
<li class=MsoNormal style='mso-list:l2 level1 lfo4'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Or, since 250.166 is written
for DC systems, is this “largest conductor” the DC source
circuit conductors (#10 in this case), and therefore the GEC can be a #8
(smallest size allowed)?<o:p></o:p></span></font></li>
</ol>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thank you in advance,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Garrison <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Garrison Riegel<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Project Manager </span></font><font
size=2 color="#1f497d" face=Calibri><span style='font-size:10.0pt;font-family:
Calibri;color:#1F497D'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><b><font size=3 color="#1f497d" face=Calibri><span
style='font-size:12.0pt;font-family:Calibri;color:#1F497D;font-weight:bold'>Solar
Service Inc<o:p></o:p></span></font></b></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>[p] 847-677-0950<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><a
href="http://www.solarserviceinc.com/"
title="blocked::http://www.solarserviceinc.com/">www.solarserviceinc.com</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>NABCEP Certified
Solar PV and Thermal Installer™</span></font><font size=2 face=Calibri><span
style='font-size:11.0pt;font-family:Calibri'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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