[RE-wrenches] Calculation of Maximum Circuit Current

[wirewiz at gmail.com]

So you pick a conductor size from 310.16 (90 deg column) and then adjust for
conditions of use. That number has to be greater than Isc x 1.25.

OCPD has to protect Isc x 1.56.

On Fri, Feb 11, 2011 at 2:18 PM, Brian Mehalic <brian at solarenergy.org>wrote:

> 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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-- 
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
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