the best wire size to use from my solar panels to the charge controller

peteja

can anyone tell me the best wire size to use from my solar panels to the charge controller? i have 12 250 watt / 50.78v at 4.92amp. with a OUTBACK MPPT FLEXmax Extreme Charge Controller. the panels is about 60 feet from the controller. from 96 to about 110 volts will come down at about 9.84 to 10.52

BB.

Re: the best wire size to use from my solar panels to the charge controller

Welcome to the forum Petaja!

Assuming you have checked the Voc-cold (voltage open circuit cold) with the maximum input of the Outback charge controller (around 140-150 VDC--Cold solar panels output higher voltages, but you are, I guess, are in Jamaica which is not very cold)... Then

The typical voltage drop is from around 3% to 1% (3% maximum recommended for nominal wiring and not "too much" energy loss and self heating to 1% which is about the cost effective minimum voltage drop--Where you are spending too much money on copper for marginal gain in efficiency).

• 50.78 Vmp * 2 = ~102 volts Vmp-array
• 102 volts * 0.03 drop = 3.1 volts maximum drop
• 102 volts * 0.01 drop = 1.0 volts minimum cost effective drop
• 6 parallel strings * 4.92 Amps per string = 29.52 amps Imp-array

Using a generic voltage drop calculator and 60 feet of one way wiring run (some calculators use round trip distance--So double check your calculator's requirements):

• 29.52.amps @ 60 foot wire run => 8 awg gives 2.7 volt drop
• 29.52.amps @ 60 foot wire run => 3 awg gives 0.8 volt drop

Based on your array and the nominal design specifications, somewhere around 8 to 3 AWG cable would be recommended. You can use heavier or lighter AWG wiring, based on your needs and available funds. In the US:

• 29.52 Amps * 1.25 NEC derating for wiring/breakers = 37 amps branch wiring/breaker minimum rating

So, you would want cable designed for a minimum of 40 amps. 8 AWG would be minimum wire size for a 40 Amp circuit.

Note, that for parallel strings of solar panels--You would need somewhere around 10-15 Amp fuses/breaker per string (use a "combiner box" -- Basically similar to wiring a normal Breaker Panel "backwards" to combine current from multiple circuits). Check the specifications for the solar panels for the Maximum "series fuse" specifications.

-Bill