wiring maximum distance for panels

[kenbob]

I was wondering how far I can run the wiring from panels to controller i purchased a roll of 100 ft # 12 , i had planned to install panels on roof of house and it will take at least 60 ft ,my panels with 2 in series produce approx 90 voc 900 watts ,do i need bigger wire or should i install them closer to controller

 

[Bop]

I work in metric (funnily enough lol) but your panels at 900w are making 10A at 90v...
60ft is 20m near enough, and 12AWG is 3.3mm^2...
Punching the numbers into Jcalc thats very borderline...
You are right on a 3% loss in the cable, with the voltage dropping from 90v down to 87.3v (you are losing 27w as heat in the cables)
Dunno about the US standards, but here a 3% loss is right at the limits legally speaking

 

[chrisski]

Use a voltage calculator and find out. Try different cable sizes and distances. Add another panel. Play with the numbers.

This is my numbers for 10 AWG guessing a vmp of 83 and 10 amps

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Find out what is tight for your situation. If you’re asking for a 100’ run, probably a good reason.