o.k., now I see where you're coming from, thank you! And yes, my brain was still in "mppt mode" when I said 390w /13v = 30a pwm. :(
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I don't think it wise to discount the possibility that a set of new panels may very well outperform their rated wattage. And other than maybe JiminDenver, the CL Solar King, most folks buy new panels to go along with their new controller purchase, especially when building a new system. So I think it may be quite responsible, on the mfg's part, to adopt a 'better safe than sorry' approach to rating controller wattage limits.
Here are some 135w poly's from 2solar:
• Maximum Power at STC(Pmax): 135Wp
• Maximum Power Voltage(Vmp): 18.12V
• Maximum Power Current(Imp): 7.45A
• Open-circuit Voltage (Voc): 21.80V
• Short-circuit Current (Isc): 7.97A
• Cell Efficiency (%): 15.72
• Module Efficiency (%): 13.61
• Temperature coefficients of Pmax: -0.47%/?
• Temperature coefficients of Voc: -0.38%/?
• Temperature coefficients of Isc: +0.04%/?
• Operating Temperature(?): -40?~+85?
• Nominal operating cell temperature (NOCT): 47±2?
130/135 = .96 x 7.97 (Isc) = 7.67 + 7% = 8.2a x 3 = 24.6a
24.6a + 25% = 30.75a
So I think maybe they have already factored in the nec allowance, as others have suggested? This would certainly be the responsible thing to do, I think. And if an OP has chosen to push 30a thru a 30a pwm, then they are in the wrong, not the manufacturer. And if by pure chance, the mfg got it right by accident, well, I'd consider that a happy accident.
And it in no way violates what is taught on this forum, as in when someone points out to a newbie such as myself, that I need to allow for that extra 25%. In my case, I allowed for even more by going 280w thru a 30a pwm. And I'm glad I did, seeing as I've seen over 18a out of the two 140's... 18a + 25% = 22.5a. If I had gone with a 20a controller, I'd likely have fried it the first season.
I was often told I would likely not see 280w... and I didn't, I saw 300w. ;)
