I'm working on my solar setup and my solar string outputs 210.41V VOC and 28.08A ISC. The cable needs to run a distance of 90m (about 290ft) one way. I've been using online calculators, but I keep getting mixed results. All these cable sizes seem massive! What would be the best cable size?
3 Answers
In commercial setups, sometimes they just use 10 AWG, even for runs over 1000ft! With your numbers, you'd likely have to use 8 AWG because 28A is a bit too much for 10 AWG to handle. That's likely going to give you a 2.3% voltage drop, which isn't too bad.
You'd typically want to go with a 4 AWG cable if you're aiming for less than a 3% voltage drop. But if you're okay with a slightly higher drop, an 8 AWG might work fine too, getting you closer to around 6%.
It's essential to clarify whether you're dealing with AC or DC here. Based on your figures, I recommend #4 AWG copper to keep a 2.22% voltage drop. But if you want to save on material costs, consider splitting your load into two circuits running at 14A each using #10s. That keeps the drop low and reduces the wire size, but be cautious of the challenges that come with it!
Different setups might require different approaches, though. If you're just meeting fire code minimums, #8 Copper or #6 Aluminum would do the trick. But if you're aiming for better efficiency, scale up those numbers!