panel wire AWG to controller
Ok so the ts-MPPT-60 is on its way, I put the card board cut outs on the roof just to make sure the panels fit as I thought and now on to more planning. I check a few voltage drop calculators for t...
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Looks like #6 for 35V*30A, if you want to stay under 4%.
Though... With #8 you'll still have close to 4%: 4.15% according to Southwire calculator. Get AWG 8 MC4 cable and call it a day. Plug and play, no rooftop junction box. You need 80ft to have 2*40ft leads, obviously.
Controller manuals recommend max 2% because NEC code says so. But people who wrote NEC didn't know much about MPPT controllers. With MPPT, V drop%= W drop%. If your 750W system has 4.15% loss at its peak time, the rest of the day (and all day in less than perfect conditions) it will have loss 2%-3%, and your total AH loss on a good day will be under 4%. Say, 194 AH with #8 compared to 198 AH with #6. IMHO, 4 AH isn't worth the trouble of running #6 and rooftop J-box.
The discrepancy btw different calculators - like same % V-drop for #10 and #2 - is due to one-way VS 2-way calculations, so people enter "2 way" when it has to be 1 way.
Though... With #8 you'll still have close to 4%: 4.15% according to Southwire calculator. Get AWG 8 MC4 cable and call it a day. Plug and play, no rooftop junction box. You need 80ft to have 2*40ft leads, obviously.
Controller manuals recommend max 2% because NEC code says so. But people who wrote NEC didn't know much about MPPT controllers. With MPPT, V drop%= W drop%. If your 750W system has 4.15% loss at its peak time, the rest of the day (and all day in less than perfect conditions) it will have loss 2%-3%, and your total AH loss on a good day will be under 4%. Say, 194 AH with #8 compared to 198 AH with #6. IMHO, 4 AH isn't worth the trouble of running #6 and rooftop J-box.
The discrepancy btw different calculators - like same % V-drop for #10 and #2 - is due to one-way VS 2-way calculations, so people enter "2 way" when it has to be 1 way.
