[RE-wrenches] DC wire sizing

[William Miller]

Friends:

Forgive me if this point has already been made:

When designing PV feeders, one typically looks at the Impp of an array for 
current specifications.  Impp is rarely achieved, however -- only  a 
handful of days per year and for only a short period of time per 
day.   This is particularly true for a fixed array.

I took the hour-by-hour data from the PV watts tool, subtracted out the 
zero values (night time) and averaged the remaining values.  The result was 
about 50%.

Therefore, a 2% VD at Impp is actually a 1% VD on average.  This gives a 
bit more headroom in any PV feeder design.

William Miller


At 04:25 AM 4/9/2010, you wrote:
>IMHO it seems like we're all really on the same page here...... trying to make
>the the most out of the the resources we have available to work with......sun
>hours, pv, copper, labor, dollars, etc. Job specifics come into play. 
>There are
>definitely times when a detailed cost/ benefit analysis is called for. Many
>other times, let's not miss the forest for the trees, an increase in wire size
>to avoid waste of other aforementioned resources, is low hanging fruit. As a
>percentage of the overall system cost, the decision is a no -brainer.
>
>Dick Ratico
>Solarwind Electic
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