PV Sanity Check

I am planning on buying a pallet of Canadian Solar 395W from sig. solar to put on my barn which is about a 130' run away from my victron 3000/24 in the house. 30 panels @ listed 11 kwh. Once I expand my lifepo4 bank, I'll be powering 18kwh/constant 750watts or so per day (but may expand to more depending on what kind of output I see).

I currently have one 150/45 MPPT. The max current is listed as 50A. I am planning to run the panels in 3S2P which according to midnite solar's calculator each "unit" of panels will produce 25.82 amps with a max VOC at -10 F at 124V.

Each of these 6 panel sets will go to an outdoor panel box where I will place my DC breakers. I plan to run each 6 panel unit back to the house with 10ga THHN in a combination of buried schedule 80 and EMT on the indoor sections. This will result in 10 conductors in the conduit.

1. With two sets of 3S2P combined (so 12 panels), that slightly exceeds max current rating for one MPPT (theoretically by 1.6 amps) - will this be okay? I will need to have 2 150/45 and another 150/35. Max amp from this should be 103.28 from 2x 3s2p plus 12.9 amps from the remaining six panels.

2. Is this enough VOC headroom (124V at -10*F) ? -10F is a generous estimated low temp for the area. We rarely see single digits here. We did see -1 a few years back.

3. Should I use a combiner box instead? I have plenty of 10ga on hand and I would prefer to not buy 8ga for that length - rough estimate it would be about $500! I purposefully ran larger buried conduit at 1.5". Indoor EMT (because of my lack of foresight) ran at 3/4 so I will need to make a second run for the indoor portions.

4. Is there a better way of doing the outdoor panel box? I would obviously prefer to have one breaker instead of five but I'm not sure if it is okay to combine all of the inputs and then split it back out again? In theory each 3s2p "unit" would be at different voltages thus this would not be possible?

5. Any suggestons on acheiving this in a better way?

What are the panel specs?
You dont use normal low temp to calculate high voc.
You use RECORD low temps.

Gotcha, thanks. Record low -25F so VOC calculates out to 126V. I assume that's still plenty of buffer from 150V?

I have a hand drawn sketch to help clarify as I'm still not confident on the panel between the solar and MPPT. I have read quite a few threads regarding what to do with the breakers and there seems to be a lot of varying opinions. Do we know for sure the MNEDC breakers will work for both overcurrent and ability to break under load? Midnite Solar's datasheet suggests their breaker can accomplish both but I've read a few threads where I still need dedicated OVPC and another that suggests to use an IMO for a load breaker?

Does this wiring scheme look okay otherwise? For simplicity only one array is drawn. Both the positive and negative I plan to have on a breaker. Even that I'm not clear if is necessary as I read that it is only needed if the system isn't grounded and elsewhere its mentioned it should always be used

I really wish Victron had more MPPT options. It is a messy hassle with not being able to combine all of this into one main MPPT channel. The 250V model I looked at but that doesn't help me with the panels I have chosen - That would let me do 5s2p but then I'm short two panels and would end up spending quite a bit more on two of the 250V MPPT vs three 150V MPPT. 6000XP looks a lot nicer when it comes to the higher voltage capacity. I would need a 48V bank but I'll need to expand my 24V regardless so that part would have been a wash