Cable size formula for solar panel wiring

**Mike90250** · 07-13-2021, 06:14 PM

Looks like you could have just 30 A from the 3 panels in parallel. That would require at least 10ga wire, adding that distance, I'd opt for 8ga. Harder to wrangle and pull, but it would give the least loss. With more than 2 panels, you need a Combiner Box or some other way for panel protection if a panel becomes damages so it does not start a fire.

**chrisski** · 07-13-2021, 07:39 PM

When laying the wire, I’d recommend you making it thicker than you need to account for growing, On top of thicker wire, if you put it in conduit, make it big enough to fit more wire.

I go to here and figure about wire with less than 3% losss:

Voltage Drop Calculator

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

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

I also check the amps running through the wire and make sure its good for less than 60 Degrees C insulation:

What is wire ampacity and how do you find ampacity rating?

https://www.wireandcabletips.com/what-is-ampacity/

When selecting a cable, one must know its wire ampacity rating. This rating has been determined by the NEC (National Electrical Code)..