4Panels in Series X 4 sizing

[West Coast Canuck]

My DIY solar system will consist of - 4strings of 4- 425watt Panels in series. Each string will be wired to the 2 ports on the 2 MPP Solar LV 6548. Each Positive line will have a 20 amp Breaker and will use 10 AWG PV wire. The wire run to the Panels will be 50-70 feet. This is my Idea any comments are gratefully accepted.

Panel VOC =49.09 x 4 in series = 196.36, Voltage drop with AWG 19 = 2.24V

Panel ISC = 10.78 x 4 in Parallel =10.78 x 1.56 temp = 16.82amps

Please let me know if I am on the right track with the calculations and wire sizing

 

[snoobler]

You use Voc for determining MPPT PV input limits. You're good there.

You use Vmp and Isc for voltage drop. Guessing panels are 37Vmp, so that puts you at 148Vmp & 10.78A.

With 10awg at 70 feet, this produces a 1.51V, 1.02% voltage drop per array.

10awg is more than adequate for the 16.82A w/safety factor, and 1.02% voltage drop works for me.

The fuse/breaker should be no larger than the panel specifies. Note that since you only have a single string on each MPPT, you do not need over-current protection to meet code, but a breaker is a handy way of disconnecting the panels.

 

[West Coast Canuck]

Thank you for you comment Vmp is 41.39v and I see a mistake on my post
Panel VOC =49.09 x 4 in series = 196.36, Voltage drop with AWG 10 = 2.24V (not AWG 19)
everything still work?

 

[snoobler]

I assumed you meant 10awg.

Not sure how you're calculating voltage drop. If you're using 16.82A, you don't need to. That's for wire rating and fuse sizing.

By running 16V higher than my previous calculation, voltage drop is lower than 1.02%, so even better.

 

[West Coast Canuck]

Thanks snoobler, for confirming my calculations, I will post a picture of the total system when complete
Thanks again

 

[Diysolar123]

Thank you for you comment Vmp is 41.39v and I see a mistake on my post
Panel VOC =49.09 x 4 in series = 196.36, Voltage drop with AWG 10 = 2.24V (not AWG 19)
everything still work?

if the distance between the panel and charge controller is 70', do not forget that you are talking about 140' of wire...
Your voltge drop will be near 3%..your wires with burn about 80watts or power.

 

[snoobler]

0.94%

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