Parallel Series Combination

[sunnyboybob]

Hey everyone first post on the forum, lots of good information on here thank you in advance for input:

I just put up 25 125 watt stion panels (76.5voc, 2.6 amp isc, 2.3amp imp, 54.13V Vmp) and installed my 2500watt sunny boy inverter ac disconnect, combiner, and dc disconnect. I just need to clarify on my panel wiring before hooking everything together for the elctric co op inspection. I was going to run 3 strings in series but have 2 panels in parallel in the first two strings and 4 panels in the last two strings wired as two parallel panels for basically 7 panels per string (if you count the parallel panels as one). I was originally going to just run 8 in series for the first two strings and two panels parallel in series in the last string but the voc calc of 76.5*8=612V which was barely over the 600v rating of the inverter. I also had read to not vary amperage on panels as this can hurt them, is wiring two panels in parallel which will double the amperage going to hurt the rest of the panels in the series string? I just wanted to make sure that this was the correct way to approach this as this is my first install.

[SunEagle]

Hello sunnyboybob and welcome to Solar Panel Talk

I would say the you should not input more than 600v to your inverter because the Voc of those panels will go up if they are cool and might overload it.

Have you thought about running your panels as 4 strings of 6 in series with one left over or 5 strings of 5? Any unequal wiring (series/parallel) of your panels could hurt you.

[sunnyboybob]

Thank you I really appreciate the reply,
I bought a midnite solar combiner that can do 4 strings with the 600v fuses so I could do 4 strings of six and leave off a panel. I thought that was the case but I had seen some people on youtube wiring an unequal amperage in series and wondered what it did. Would this just drag down the amperage of the parallel wired panels and hurt the life of the other panels, or is it from a standpoint of offering more output if I do 4 equal amperage series strings (or a combination of both haha)?

[sensij]

Thank you I really appreciate the reply,
I bought a midnite solar combiner that can do 4 strings with the 600v fuses so I could do 4 strings of six and leave off a panel. I thought that was the case but I had seen some people on youtube wiring an unequal amperage in series and wondered what it did. Would this just drag down the amperage of the parallel wired panels and hurt the life of the other panels, or is it from a standpoint of offering more output if I do 4 equal amperage series strings (or a combination of both haha)?

Four strings of 6 is a much better design. I would guess that the amperage won't get dragged down much in your proposed design, instead, the current from the paralleled panels will just bypass the single panels in the string, so they won't contribute to power generation at all and the string voltage will be reduced. If the bypass diodes in those panels fail, then the string current will suffer and it will be hard on the single panels.

[inetdog]

Hey everyone first post on the forum, lots of good information on here thank you in advance for input:

I just put up 25 125 watt stion panels (76.5voc, 2.6 amp isc, 2.3amp imp, 54.13V Vmp) and installed my 2500watt sunny boy inverter ac disconnect, combiner, and dc disconnect. I just need to clarify on my panel wiring before hooking everything together for the elctric co op inspection. I was going to run 3 strings in series but have 2 panels in parallel in the first two strings and 4 panels in the last two strings wired as two parallel panels for basically 7 panels per string (if you count the parallel panels as one). I was originally going to just run 8 in series for the first two strings and two panels parallel in series in the last string but the voc calc of 76.5*8=612V which was barely over the 600v rating of the inverter. I also had read to not vary amperage on panels as this can hurt them, is wiring two panels in parallel which will double the amperage going to hurt the rest of the panels in the series string? I just wanted to make sure that this was the correct way to approach this as this is my first install.

If you put two panels in parallel in only one position of a series string it will be the same as putting one double current panel in that position. The effect will be that the double panel will be restricted to producing only the same current as the rest of the string, but as a voltage which is maybe a volt or two higher than a single panel. In short you will be wasting the potential power from those two panels. Better to install only one and keep the second as a spare.

If you measure the short circuit current of the whole string you will get double the current, but only because the bypass diodes in the other panels of the string are being activated. The results under MPP load will be essentially the same as a single panel.

Panels in a series string going into an MPPT device should have current ratings (Vmp) which are within 5% of each other to limit wasted power.