I see it’s a good idea to add FUSES to the panels connected in parallel… each panel has a Short Circuit Current of 10.72 A so I presume I’ll need 8 for 2 arrays of 4 panels in parrallel plus 2 more for the combined arrays entering DC1 and DC2 … ?
AI (lol) is suggesting I use 20A fuse for each panel in parallel (8 in total) and then get a 60A DC Circuit Breaker for each of the combined arrays.
Your info is not clear but one thing that won’t work is having a series array and several parallel panels on the same input, as you’re mixing very different voltages. If you meant them to be either one option or the other, that will work, but you cannot have both options at once on a single input.
DC1 and DC2 will both have to be either one string in series, or two series strings in parallel to each other; you will damage your solar panels if you try to have one series string in parallel with 4 individual panels. DC1 can be different to DC2 though.
As a general rule, the MPPT will be more efficient at a higher voltage, so you should prefer strings in series; unless you have to consider shading, or if you’re going DIY then legal restrictions on maximum string voltages may apply in your country, and that will mean that you need to run panels in parallel. Bear in mind that more panels in parallel also means more current, and therefore costlier cables and equipment.
You need to make your information clearer, or fix your panel configuration, before anyone here can help you get the right fuse size.
The reason you want 20A fuses is due to backfeeding. The reason they suggest 20A is just a rule of thumb which is ISC X 1.25 X 1.25 (or ISC X 1.56) which accounts for continuous operation and overhead. Your panel is 10.72ISC so 10.72X1.56= 16.7A. Fuse sizes come in 15A (too less) and the next size available is 20A. By placing a fuse between each panel you prevent too much backfeeding. Generally if your parallel string is 2 or less you DO NOT need a fuse, but since yours is 4, you want a fuse at each panel.
You might want to consider running in a 2S2P configuration, which would put you around 48/16 for each 4 panel array, or a total of 96/32 for DC1 and DC2. Less heat, still safely within VOC limit. Less risk of backfeeding.
That would work fine. You have enough buffer to cover for voltage spiking slightly due to temperature coefficient of panels in cold weather. For example at 0F/-17C your 24V panel would produce 27V assuming the standard loss of -0.30% per degree C below 25C. This puts you at around 135V for the array which is below the 150 you are maxed out at. The only drawback is your MPPT controller only supports a max of 12A per DC input, so while you are pushing 16A through, it will reject the remaining 4A, so the array on DC1 would be 120.4X12 or 1440W, not 2000. While that’s not ideal, you would benefit from shading/cloudy days thanks to overpaneling. On a sunny day, yes each 200W panel would produce 8A but that current drops to 25% on mostly cloudy and around 10-12.5% on extremely overcast days. What is 12.5% of 8A? Just 1. This means you will have 120W per string roughly or 240W for DC1 and 240W for DC2 for a total of 480W in the worst case cloudy scenario. Double 12.5% is 25% so if clouds shade to 25% it would be 960W total (120V/8A) and since you can only get 12A you are maxed out to just 1440W or 72% of your array potential maximum. The max input per channel is 100V@12A or 1200W so while your solar panels CAN produce 1440W each channel is limited to and will be throttled to 1200W. MPPT will just reject the rest. So 1200W max on DC1 and 1200W max on DC2.
Solar investments can get out of control fast so you really need to buckle down on what specifically you want out of your system. Are we talking a whole home rooftop replacement OR just enough to get you through those brownout days? It’s called “system sizing”. Your setup is capped by your MPPT controller which supports up to 150V. Your roof space is capped by the limited PHYSICAL space. Then of course there is cost. Personally I would rather invest into the battery ecosystem of Bluetti rather than its solar ecosystem because it is far more cost affordable and replaceable to have multiple MPPT controllers than it is to invest heavily into Bluetti’s system if something fails. I’m perfectly happy with their small portable power stations and foldable panels, but never would I dump $10k on solar. A few grand for 8-10Kwh worth of home backup batteries to cover an outage for a few days to a week? Sure! But not anything else. Lots to weigh here. For example the shape, size, and wattage output of the solar panels. 400W means more solar potential, but also more cost to replace if it goes bad. Easier to replace a cheaper 200W panel than a more expensive 400W+ one. In your current setup, without the Bluetti Solar 4X to increase the voltage above 150V, the ONLY thing that makes sense right now is 200W panels.
Principal use is emergency cover Fridge/Cooker and light - but I’ll probably end up using it as a UPS for cctv wifi and pcs - sometimes the power is off and on here 3 or 4 times a day.
But I’ll use it as a learning tool and see where things go later - I’d like to go off grid but until I sort a few other things I won’t really know my expected kwh…
