Very good. Thank you Peter. On Fri, Feb 11, 2011 at 2:44 PM, Peter Parrish < [email protected]> wrote:
> Short answer: DC/PV side two factors of 1.25; AC side one factor. > > Reasons: the common factor of 1.25 is due to the treatment of PV systems as > continuous sources of power, the second factor of 1.25 is for the "cloud > effect". It is entirely possible to get more than 1,000 W/m^2 on a PV > module > if there are large cumulus clouds that don't block the sunlight but act as > pretty good reflectors of sunlight. > > As a result you need to increase Isc (times the number of combined strings > if that is the case) by 1.56, and all computed AC currents by 1.25. Same > goes for and switches and OCPDs. > > Then of course you need to compute the ampacity of the wire being used, > taking care to apply the temperature correction and conduit fill > correction > before comparing to the "maximum current" calculation. > > - Peter > > > Peter T. Parrish, Ph.D., President > California Solar Engineering, Inc. > 820 Cynthia Ave., Los Angeles, CA 90065 > CA Lic. 854779, NABCEP Cert. 031806-26 > [email protected] > Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Friday, February 11, 2011 11:03 AM > To: [email protected] > Subject: [RE-wrenches] Calculation of Maximum Circuit Current > > In studying for NABCEP certification I am a little confused about whether > you multiply the short circuit current by 1.25 once or twice (1.56) in > order > to calculate maximum circuit current in determining wire size. Same for > overcurrent protection. > > I have always done it twice (1.56) for both PV source circuit and PV output > circuit. Once for over irradiance and once for continuous use. > > But a handout at a recent seminar that I went to totally confused me. > > Can anyone spell it out very clearly? > > Thank you. > > Larry Liesner > Wirewiz > Westport, CT > Phone: 203-644-2404 > Fax: 203-557-0556 > [email protected] > www.wire-wiz.com > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > -- Larry Liesner System Design Elektron Solar, LLC 16 Ketchum St. Westport, CT 06880 203-557-3127 (office) 203-644-2404 (cell) 203-549-0977 (fax) [email protected]
_______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
