Yes, they are 100% duty rated. Also, a little-known fact about the CBI
breakers used by Midnite and Outback, gleaned from conversations with
Robin Gudgel: because of this hydraulic/magnetic construction, all are
capable of controlling both AC and DC, even if not listed as both.
robert ellison wrote:
I believe that the breakers from CBI, Midnite and Outback are
hydraulic / magnetic and may be operated at 100% While the derating
applies to all others that are Thermal / magnetic,
Bob
On Fri, Apr 2, 2010 at 11:14 AM, Kent
Osterberg <k...@coveoregon.com>
wrote:
Erika,
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.
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.
Kent Osterberg
Blue Mountain Solar, Inc.
Erika M. Weliczko wrote:
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.
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%.
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.
I am going to
stick to the fact that the circuit has to carry the 156% under all
conditions…
Thoughts?
Erika
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