[RE-wrenches] Calculation of Maximum Circuit Current

[Brian Mehalic]

Maximum current is defined in 690.8(A) as Isc x 1.25.

Minimum OCPD size is defined in 690.8(B) as maximum current x 1.25 (Isc x
1.56).  The maximum size, for PV source circuits, is the module maximum
series fuse size.

Required conductor ampacity is the greater of Isc x 1.56 or Isc x 1.25 with
all conditions of use factors (and the conductor must be protected by the
OCPD under conditions of use).

Brian

On Fri, Feb 11, 2011 at 11:03 AM, <wirewiz at gmail.com> wrote:

> 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
>
>
>
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-- 
========================
Brian Mehalic
NABCEP Certified Solar PV Installer™
PV Online Coordinator
Solar Energy International
Carbondale, CO 81623
http://www.solarenergy.org
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