More strings with less panels or less strings with more panels!

[livewire1]

I was curious, say for instance if I have 2 strings producing 2100 watts @ 5 amps per string would it be better to have 3 strings producing 2100 watts @ 5 amps per strings. The real question is the amperage of having 3 0r 2 strings. Im guessing the 3 strings would be better, but Im asking just in case. Thanks

[lile001]

I was curious, say for instance if I have 2 strings producing 2100 watts @ 5 amps per string would it be better to have 3 strings producing 2100 watts @ 5 amps per strings. The real question is the amperage of having 3 0r 2 strings. Im guessing the 3 strings would be better, but Im asking just in case. Thanks

Well, it doesn't really matter how many panels you string together, EXCEPT you must stay within the voltage limits of your panel, your inverter (or charge controller) and keep in mind the NEC required 125% or so fudge factor for cold weather. You see, a solar panel can produce higher voltage at low temperatures, depending on how cold it gets in your neck of the woods, you have to boost the open circuit voltage of your string by a fudge factor. Make sure you are adding Voc to get the maximum string voltage, not the maximum power point voltage which might be as low as half of Voc!

Meanwhile, your inverter has a sweet spot for input voltage. My SMA inverter likes 240VDC input, it's efficiency is highest in that range. Your inverter might be different. I'd optimize your string voltage for the maximum inverter efficiency (this time using the maximum power point voltage, not Voc).

Quite often, all of these factors will dictate a maximum number of panels lower than you'd guess.

[fromport]

I was curious, say for instance if I have 2 strings producing 2100 watts @ 5 amps per string would it be better to have 3 strings producing 2100 watts @ 5 amps per strings. The real question is the amperage of having 3 0r 2 strings. Im guessing the 3 strings would be better, but Im asking just in case. Thanks

I think you would let the effiency of your inverter decide that.
Most of the inverters i've worked with like higher voltages better (more efficient) than lower (still within range).
If there is a possibility of shading, i would rather have more strings.

[Shanghai-sparky]

I was curious, say for instance if I have 2 strings producing 2100 watts @ 5 amps per string would it be better to have 3 strings producing 2100 watts @ 5 amps per strings. The real question is the amperage of having 3 0r 2 strings. Im guessing the 3 strings would be better, but Im asking just in case. Thanks

How many modules in each string? Your math does not add up if you can have two or three strings with both having 2100 watts and 5 amps unless you use lower voltage modules for one of the strings.

[Mike90250]

Fewer strings, higher voltage, to the limit of the inverter on a cold day, reduces the "copper loss" of amps in wires. Inverter efficency begins to fall off, if input voltage is way above the sell voltage, but it's only a couple %. Better manuals will have charts.

[solar_geoff]

Fewer strings, higher voltage, to the limit of the inverter on a cold day, reduces the "copper loss" of amps in wires. Inverter efficency begins to fall off, if input voltage is way above the sell voltage, but it's only a couple %. Better manuals will have charts.

AMEN!

I recommend using the fewest strings possible with the most modules per string to reduce BOS costs/components.

Thats the whole idea behind bipolar inverters and 1200V max DC utility systems, since it is current not voltage that requires you to use bigger wire.