help calculating wire size! which inputs? is this correct?

[Jamie.sanders]

I am trying to built my own system and learning,
I am trying to calculate the size wire needed from my panels to combiner box, and from combiner box to charge controller.

my specs are
6x440 watt panels
WIRED 2S3P
VOC 52.6
VMP44.3
ISC 10.53
IMP 9.93

its about 12 feet to combiner box and 230 feet to charge controller.

so from the panels to combiner box, I should enter 9.93amps, 52.6Volts and 12 feet?
and from the combiner box I should enter 30 amp, 105 Voltage 230feet

What I am getting is to the combiner box should be 12 gauge, and to the charge controller should be 2 gauge.
can someone double check me please, I don't want to waste money on the wrong size wire, and several wire calculators give
different answers?
thanks in advance.

 

[Supervstech]

Take the max amperage of the circuit, and factor in ampacity, then length, decide on acceptable voltage drop, and you have a number for a calculation.

I would use the 10.53A as a max amp. #14 would be ok ampacity, but voltage drop would be around 15% with long conductors.
The parallel output would be 3x the max amps, or 31.59… #10 would be an absolute minimum. Ampacity for free air conductors. If in conduit, #8
Voltage drop could be in the 10% range, so up to you if acceptable…

 

[MichaelK]

Since you have such a long run to the charge controller, I'd recommend wiring in 3S2P instead of 2S3P. Here are the numbers passed through Midnight's string calculator. https://www.midnitesolar.com/sizingTool/index.php

Importantly, what are your winter low's like? I set the winter low in this calculation for 0F. Is that low enough for you?

With a Voc of 180V, you will need a controller that can handle 200V. Looking at your output, I'd say that Epever's Tracer6420AN would work for you.

In terms of the wire run, that would be about 18A running from the combiner to the controller. Here is the voltage drop calculator I like to use.

Voltage Drop Calculator

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

www.calculator.net

The voltage drop is significant, but it will be a judgement call as to whether or not you want to spend more money on more copper to reduce the drop.


10 gauge will safely handle almost twice the number of amps you are putting through, so you could get by with standard 10AWG wire and just accept a bit more voltage loss. Or 8AWG if cutting voltage drop lower is most important. Plug in your own numbers and decide for yourself.

 

[Jamie.sanders]

Since you have such a long run to the charge controller, I'd recommend wiring in 3S2P instead of 2S3P. Here are the numbers passed through Midnight's string calculator. https://www.midnitesolar.com/sizingTool/index.php

Importantly, what are your winter low's like? I set the winter low in this calculation for 0F. Is that low enough for you?
View attachment 75355
With a Voc of 180V, you will need a controller that can handle 200V. Looking at your output, I'd say that Epever's Tracer6420AN would work for you.

In terms of the wire run, that would be about 18A running from the combiner to the controller. Here is the voltage drop calculator I like to use.

Voltage Drop Calculator

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

www.calculator.net

The voltage drop is significant, but it will be a judgement call as to whether or not you want to spend more money on more copper to reduce the drop.
View attachment 75358View attachment 75360

10 gauge will safely handle almost twice the number of amps you are putting through, so you could get by with standard 10AWG wire and just accept a bit more voltage loss. Or 8AWG if cutting voltage drop lower is most important. Plug in your own numbers and decide for yourself.
View attachment 75361

Thanks, and great info but I already have the Midnight 150. don't want to buy another, Guess I should have done
more research and learned more before pulling the trigger on items, but I'm excited about doing this.

 

[Jamie.sanders]

and yes, I'm in central Arkansas, the record low ever was -5, and that was dead at night with no sun

 

[MichaelK]

and yes, I'm in central Arkansas, the record low ever was -5, and that was dead at night with no sun

Nighttime is not what is important. At dawn the first rays of morning light will make the panels put out their highest voltage even if the amperage is next to nothing. It's the voltage that will fry your electronics. Even moonlight might put out power to fry it.