Madco
Solar Enthusiast
So don't shoot the messenger, but ...As for ampacity of the #10 - If this table is right I think I should be OK?
View attachment 162912
30*.8= 24 and my short circuit current is 11.54a. Run in series, each string with 11 panels, it should be open circuit voltage 538v, 11.54a. I suppose I could even drop to 12awg? I don't have the specs of this particular MC, but looks like solid copper if that makes a difference.
You need wire of basic ampacity of 11.54*1.25*1.25 = 18A. That is then derated for the fill (factor of 0.8), or 18/0.8 = 22.5 A. Then, the temperature derate. I don't know what type of wire is in the MC or your attic temperature, but assuming 75C wire and an attic temp of 130F, the temp derate is 0.67. So now you need 22.5/.67 = 33.6A, just over the 30A given in the amapcity table. Even with 90C wire, you're still over what #10 allows, but still just slightly.
BTW, the extra 1.25 comes in because of cloud edge effects.