Eirka:
Although the Imp is your normal operating condition, you need to design
wire size for an abnormal occurrence (short circuit or other fault). You
do not want the wire to burst in to flame after an unplanned short circuit,
do you? Remember, you may have combiner fuses, but you have no overcurrent
protection to open circuits when a fault occurs in a PV feeder. See
http://millersolar.com/practices/Safety/safety_data.html , click on Target
PV fire.
Correct wire sizing is not a waste of money. Loosing output power due to
wire heating is a waste of money. Burning down the house is a waste of money.
William Miller
At 06:27 AM 4/2/2010, you 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 conditionsÂ…
Thoughts?
Erika
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