[RE-wrenches] 1.56 Rule

[Ray Walters]

If you use 100% duty rated breakers such as breakers sold my Midnite, 
you can ignore the 1.25 multiplier for continuous duty.

Ray Walters
Remote Solar

On 5/18/2026 8:27 AM, Dave Tedeyan via RE-wrenches wrote:
> I agree with David. I think the first 1.25 is for continuous use, and 
> the second is for when irradiance is higher than the standard 
> 1000w/m2. I've also seen irradiance around 1200 in cloudy central NY.
>
>
> On Mon, May 18, 2026, 3:36 PM David Quattro via RE-wrenches 
> <re-wrenches at lists.re-wrenches.org> wrote:
>
>     The standard assumed irradiance for math purposes has always been
>     1000W/m2. I’ve seen days where base-line was 1200 on my Daystar
>     meter, and elevation was barely above sea level, say 500ft, max
>     1000ft. I imagine Edge of cloud effect on a day like that could
>     send the current as high as 1.56
>     David
>     *
>     *
>
>
>     On Mon, May 18, 2026 at 6:24 AM Dana Orzel via RE-wrenches
>     <re-wrenches at lists.re-wrenches.org> wrote:
>
>         VERY High elevation 10,000’+ , with high wind & very low
>         temps. Not normal installation definitely a “Special”
>         situation.  I agree in 95% of installations 1.56 is an excessive.
>
>         _________________________________________________________
>
>         Dana Orzel GREAT SOLAR WORKS!
>
>         C – 208.721.7003      E – dana at solarwork.com
>         <mailto:dana at solarwork.com>
>
>         W - www. greatsolarworks.com <http://greatsolarworks.com>
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>
>         ---------- Forwarded message ----------
>         From: Drake Chamberlin via RE-wrenches
>         <re-wrenches at lists.re-wrenches.org>
>         To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>         Cc: "drake.chamberlin at redwoodalliance.org"
>         <drake.chamberlin at redwoodalliance.org>
>         Bcc:
>         Date: Mon, 18 May 2026 13:09:27 +0000
>         Subject: [RE-wrenches] 1.56 Rule
>
>         The logic of this rule for calculating PV amperage seems a
>         little off to me. - It is a calculation that is set in stone
>         as a bedrock truth of the solar industry. (1.25 X 1.25 = 1.56).
>         The multiplier of 1.25 for a continuous load is relevant for
>         sure. To multiply again by another 1.25 seems excessive.
>         Although it is certainly true that modules put out
>         considerably more power when it is cold out, in my experience
>         that is almost all due to the increase in voltage. The
>         amperage goes up a little, but no where near 25%.
>         Just because I haven't seen it doesn't mean it can't happen.
>         Are there circumstances where the amperage of a PV module can
>         go up by 25%?
>         Thanks,
>         Drake
>
>         /Drake Chamberlin/
>
>         /Athens Electric LLC/
>
>         /Ohio Electrical Contractor’s License 44810/
>
>         /NABCEP Certified PV Installation Professional/
>
>         -- 
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