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Erika,<br>
<br>
You should refer to NEC 690.8 this information. There are two issues
that contribute to the 1.56 factor. First is that the maximum current
from the PV array is considered the short circuit current multiplied by
1.25 to account for higher than standard irradiance such as cloud edge
effect, high altitude, and high operating temperature. The second
multiplier of 1.25 is because PV current is considered to be
continuous. All conductors (and breakers) operating continuously (over
three hours I believe) that are subject to NEC rules are limited to 80%
of the ampacity in Table 310.16. The two 1.25 factors equals 1.56.<br>
<br>
For normal operation, wires selected under this criteria are
conservatively rated. But it is also the objective of the NEC to
design power systems in a manner that they will remain safe under
abnormal circumstances.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
<br>
Erika M. Weliczko wrote:
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<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">To my
understanding the 156% on PV source
and output circuits is related to the ability of PV to deliver more
than rated
and be continuous.</span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">Therefore, the
wire has to be able to
carry this current, so now the temperature and fill corrections are
applied to
find the wire capable of the 156%.</span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";"> </span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">I am in a
debate where the question is why
correct for temp and fill on 156% of ISC and spend all that extra money
when
the normal operating is at Imp. Or why correct the 156% but why not
correct the
Isc or Imp.</span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";"> </span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">I am going to
stick to the fact that the
circuit has to carry the 156% under all conditions…</span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">Thoughts? </span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";"> </span></font></p>
<p class="MsoNormal"><font face="Century Gothic" size="2"><span
style="font-size: 10pt; font-family: "Century Gothic";">Erika</span></font></p>
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