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.