DC to AC Conversions Calcs.... [RE-wrenches]

[Peter Parrish]

Hi Kirpal.

To begin with, you need a definition of "kW-AC", otherwise you are just
guessing. Find out from the State of Oregon License Board how they define
"kW-AC". Then do the math. In California is it defined as N*P-ptc*Eff, where
N is the number of modules, P-ptc is the CEC rating of the PV module, and
Eff is the CEC rating of the inverter efficiency. 

But with a NABCEP certification, you know all that right? What am I missing?

If you want to drill down into insolation, orientation, inverter efficiency,
electrical losses, shading, down time, etc, look at PV Watts. The answers
that the PV Watts calculator gives (using the default values for all the
coefficients save inverter efficiency and shading in the DC-AC derate
factor) are fairly conservative, and are borne out in practice.

- Peter

Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com 

-----Original Message-----
From: Kirpal Khalsa [mailto:solarworks at gmail.com] 
Sent: Wednesday, June 11, 2008 8:30 PM
To: RE-wrenches at topica.com
Subject: DC to AC Conversions Calcs.... [RE-wrenches]

Hi All......In Oregon the license for non electrician solar installers
is a LRT license.......This license is valid when working on a
permitted system up to 25kW AC.......What calculations might you all
use when determining the AC size of the system.........besides the
obvious.....Inverter efficiency losses de-rating and wiring losses
de-rating?   I am trying to determine what the maximum size in terms
of a DC system would be able to be installed and not exceed the 25kW
AC system cap.....How might you all interpret that?
Thanks.....

-- 
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer TM
Renewable Energy Systems


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