Correct size combiner box; ideas?


A little bit too anxious & impatient to wait for the solar salesmen to come back from their weekend break to get answers.... so I was hoping I could bend your ears/eyes until then.

Here's my situation....

I will have two separate arrays with an equal number of panels on each that are of the same make (SolarWorld175) that are going to be put together soon. The run is about 200 ft or so from the panels to the house. I've been told it is best not to combine all the panels at the poles and send all current over the same #2AWG copper wire. Fortunately, I have two poles and each have #2 wire running to the house.

Each array has a combiner box at the base of poles that connects 8 panels (48v system; 16 ttl panels).

Each is/will be sending power to the house were I would like to combine them once again so I can have them all going into my Flexmax 60.

The wires coming into the house are copper #2AWG. Is this too big for most combi boxes???

The wires going into the Flexmax60 are #6AWG.

What boxes would work best?
Would the Midnight Solar MNPV3 be adequate?
Fuse or CB size?

SW175 Amperage.... Short Circuit Current=5.3A; Max Power Point current=4.89A

Open to any ideas &/or suggestions!

Thanks in advance!!!!!


  • dsp3930dsp3930 Posts: 66Solar Expert ✭✭✭✭
    Re: Correct size combiner box; ideas?

    Assuming 35.7V ea panel and that you have a hybrid (grid/offgrid) or offgrid 48v system....

    You likely have four strings of two panels per pole. (71.4V per string) That makes about 19.56A per array. Each 8 panel array would need at least #3 wire for less than 2% loss at 200 feet. You would need 1/0 wire if both arrays were combined into one wire from your array and run to your charge controller.

    #2 is too big. You will need to step it down to #6 for most charge controllers.

    I don't see an issue using another combiner box inside like the MNPV3 using 30A breakers to use as switches and then running from there to your charge controller.
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