AC, Battery & Solar Distance Wire Sizing Calculations

AC Loads and Supply : Use the standard AWG wiring charts for your AC Load, found online e.g. https://www.powerstream.com/Wire_Size.htm (use the Max amps for power transmission column)

Battery:

  • Use the Battery cable suggestion in the manual, keep cables as short as possible, when in doubt, choose a thicker cable or double-up
  • Battery Max amps = rated Inverter output x 2 / battery Voltage, example 24V , 2.4kW rated output x 2 / 24V = 2400 x 2 / 24 = 200A

Solar Wiring :

  • This can be easy or tricky
  • I try to keep my cable losses to less than 3% but its all based on the $$$
  • This calculator is my friend:  
  • Distance* (this is one way – if your panels are 150ft away, use 150ft)
  • Load current – Calculated in previous slide, num of parallel strings x Impp

Example:

  • My Panels are located 150ft from my inverter, 3450W array connected in 2s5p
  • Vmp = 75.86V, Impp = 45.45A, 
  • Im thinking 8 AWG would be fine, lets see what the loss will be
  • Wire Material – Copper
  • Wire Size – 8AWG
  • Voltage – 75.86V
  • Phase – DC
  • Number of conductors – single set of conductors
  • Distance – 150 ft
  • Load current  – 45.45 Amps
  • click “Calculate”
  • Gives me a ridiculous 11.29% volt drop
  • I try “2 conductors per phase in parallel”
  • Result -> 5.65%
  • I try 6 AWG , “single set of conductors”
  • Result -> 7.10%
  • I try 6 AWG , “2 conductors per phase in parallel”
  • Result -> 3.55%

I determine that’s close enough for me, I go online to HomeDepot.com order myself a 500 ft. 6/1 Red & Black Stranded THHN Wire

I run two red wires and two black wires in my conduit for EACH solar array of 3450W from the panel combiner box to my inverter in my basement.

I do the same for each of my solar arrays,  I may use a different color combination for the next array.

Remember to ground your Solar Panel array frames right where they stand  (long ground rod)

And you’re done.

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