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:

https://www.calculator.net/voltage-drop-calculator.html

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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