Design check

notes

Thanks for this forum and its members, ( Cariboocoot, Chris Olson, to Dave Angelini and BB ) and all in between. 
Equipment I have: 2 Trace SW4024, I know they are NLA. Only using one. I have no 208/240 loads.
4-6 Canadian Solar CS6U330P, They fell in my lap.
What I am scratching my head on is distance from panels to charge controller. (250' )
I need to build a new generator shed and power room. I am considering cutting distance in half and extending propane and 120 volts, 
hopefully using #8 or #10 wire. Any help would be greatly appreciated.

Estragon

250' (from combiner box to CC?) with 8ga ~7% voltage drop... maybe a bit high:

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=75&phase=dc&noofconductor=1&distance=250&distanceunit=feet&eres=17&x=57&y=23

If the new genshed location has good sun, 125' would be much better.  Generally, 3-5% is considered "acceptible". 

With a 24v bank and strings of 2 though, even with 7% drop you'd still have good headroom for mppt - just a matter of whether you're ok with a few extra % losses.  

Another alternative would be to use a Classic 200 and higher string voltage for the 250' location.

BB.

If the shed is a 125 feet from your home/office... You might wish to look at higher voltage array (and possibly a charge controller) to keep the stuff you want to keep an eye on closer to where you live.

For some examples... 2p x 2s panels, 250 feet, 3% drop, Vmp~37.2 and Imp~8.88 amps. Assume cold climate and Vmp-array~100 VDC max... That means 3 panels in series with the Outback FM controller is not a good fit (check your low temperatures and maximum Voc-cold for your panels).

Using a voltage drop calculator with 8 AWG cable:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=74.4&phase=dc&noofconductor=1&distance=250&distanceunit=feet&amperes=17.76&x=78&y=20
Voltage drop: 5.58
Voltage drop percentage: 7.50%
Voltage at the end: 68.82

You would need 5 AWG or heavier cable to get below 3% drop.

Just for interest, you have 6 panels? 6 panels in series (37.2v*6=223.2 volt Vmp-array) and 8.88 amps Imp-array. Playing with the calculator for 3% or lower drop:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.2
77&voltage=223.2&phase=dc&noofconductor=1&distance=250&distanceunit=feet&amperes=8.88&x=61&y=22
10 AWG:
Voltage drop: 4.43
Voltage drop percentage: 1.99%
Voltage at the end: 218.77

And with 6 panels:

• 6 panels in series * 37.2 Vmp * 8.88 Imp=1982 Watt array
• 6 * 37.2 Vmp = 223.2 Vmp-array (STD)
• Need a MPPT controller with Vpanel input minimum voltage ~ 335 volts (SWAG)
• 1,982 Watt array * 0.77 panel+controller derating * 1/29 volts charging = 53 Amp minimum rated charge controller

Both Schneider and MorningStar (Outback now or soon?) have controller that will take Vpanel~600 volts, and Vmp-array-std~400 volts.

They are not cheap. 

Schneider Electric Conext XW MPPT 80 Amp 600VDC Solar Charge Controller ($1,180)
Morningstar TriStar 600 Volt 60 Amp MPPT Solar Charge Controller With Transfer Switch ($1,780)
Morningstar TriStar 600 Volt 60 Amp MPPT Solar Charge Controller With Transfer Switch and GFPD
Morningstar TS-MPPT-60-600V-48-DB TriStar 600 Volt 60 Amp MPPT Solar Charge Controller & Disconnect Box
Morningstar TS-MPPT-60-600V-48 TriStar 600 Volt 60 Amp MPPT Solar Charge Controller
OutBack Power FM100-300VDC FLEXmax 100A MPPT Solar Charge Controller ($880--works to Vmp~200 volts)

If you use the 80 amp Schneider, you could bump up your array to:

• 80 amps * 1/0.77 panel+controller derating * 29 volts battery charging voltage = 3,013 Watt array
• 3,013 Watt array / 330 Watt panels = 9.1 = 9 panels in series (based on Watt rating)
• 400 volts Vmp / 37.2 volts Vmp per panel = 10.8 panels = 10 panels in series (based on Vmp-array-std max rating for cold climates).

If you were able to justify a new Schneider 80 amp 600 volt (input) charge controller, you could have up to 9 of those 330 Watt panels in series and max out your charge controller. And for 3% drop, your array wiring could keep the 10 AWG wiring to the 250 foot distant array:

9*37.2v=335 Vmp-array, Imp-array=8.8 amps, 250 foot one way run, 10 AWG cable:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=335&phase=dc&noofconductor=1&distance=250&distanceunit=feet&amperes=8.88&x=37&y=19
10 AWG:
Voltage drop: 4.43
Voltage drop percentage: 1.32%
Voltage at the end: 330.57

And you could go 12 or even 14 AWG with not too bad losses:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=8.286&voltage=335&phase=dc&noofconductor=1&distance=250&distanceunit=feet&amperes=8.88&x=62&y=25
14 AWG:
Voltage drop: 11.21
Voltage drop percentage: 3.35%
Voltage at the end: 323.79

It is easy to spend somebody else's money. 

-Bill