[RE-wrenches] Calculation of Maximum Circuit Current

[wirewiz at gmail.com]

Very good. Thank you Peter.

On Fri, Feb 11, 2011 at 2:44 PM, Peter Parrish <
peter.parrish at calsolareng.com> 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
> peter.parrish at calsolareng.com
> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
>
>
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
> wirewiz at gmail.com
> Sent: Friday, February 11, 2011 11:03 AM
> To: RE-wrenches at lists.re-wrenches.org
> 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
> wirewiz at gmail.com
> www.wire-wiz.com
>
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> 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: RE-wrenches at lists.re-wrenches.org
>
> 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)
wirewiz at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20110211/1db0141e/attachment-0003.html>