wiring panels into combiner box

[larrybc1]

Hi to All,

I have the following setup--just want to make sure I am doing it right!
I have 25 evergreen 210 watt panels==22.8 VOC, 18.3 VMP and 11.48 IMP
plan to set them up as 3 strings of 5 panels into FM-80 charge controller and
2 strings of 5 in the other FM-80 controller. I am using the MC4 extension 10awg wire to connect to the combiner box after I wire the panels in series .....plan to put the 3x5 and 2x5 as above into MNPV-6 combiner box with 5- 20amp breakers..Then feed out of the combiner box into both controllers.. the run to the controllers will be about 50 feet so what size wire would I have for that? does this look OK or am I missing anything?..I also plan to ground all of the panels with grounding lugs..thks Larry

[Sunking]

What battery voltage are you using?

One thing I see wrong is you need to make at least 2 separate systems feeding a common battery. That means 2 combiners.

[larrybc1]

What battery voltage are you using?

One thing I see wrong is you need to make at least 2 separate systems feeding a common battery. That means 2 combiners.

It is a 48 volt system..So you think I need 2 combiner boxes--one for each controller?..I have 2 seperate controllers..I was told that I* could run all 5 strings thru the MPNV-6 combiner box and then come out of the box with 2 lines--one to each controller ..it shows that on the pamphlet diagram for the combiner box thks for the help Larry

[Mike90250]

You need to be sure the combiner box, will let you feed 3 strings to one controller, and 2 strings to the other. If they use a common buss inside, that can lead to the 2 controllers fighting over one 5 string array.

[larrybc1]

You need to be sure the combiner box, will let you feed 3 strings to one controller, and 2 strings to the other. If they use a common buss inside, that can lead to the 2 controllers fighting over one 5 string array.

ok Mike..will call Midnite tommorrow..thks for the help..What size wire shud I run from the combiner box to the controllers..Run will be about 50 feet...#4awg wire? that what I was figuring thks Larry

[TnAndy]

The Midnite box does have a common bus, so you can't "split" between controllers. What you need are two MNPV-3 boxes.....feed the 3x5 into one, and then to one of the FM-80s, and 2x5 into the other, and to the other FM-80. Wire size, #6 copper will be fine on 50' run

[Sunking]

It is a 48 volt system..So you think I need 2 combiner boxes--one for each controller?..

Larry for one it was a trick question because no matter what answer you gave, it would be the wrong answer, it will not work for 2 reasons.

1. You are using 12 volt panels on a 48 volt battery system. With just 3 panels in series can only be used on 12, 24, and 36 volt systems, not 48 volts. You need a minimum of 4 panels in series. Read page 76 of the owners manual. Minimum Vmp voltage must be equal to or greater than 60 volts. With 3 panels in series only gets you 55 volts. The FM-80 is a BUCK controller which means it can only down convert voltage, not up.

2. Each charge controller needs its own dedicated panel system. You cannot combine two systems on the inputs. You can however parallel the outputs to a common battery . So YES is the answer to your question. You will need 2 combiners and will have to loose at least 1 panel. Make both systems EQUAL in power or identical.

On second thought you can run two systems of 5 x 3 and 5 x 2.

[Sunking]

What size wire shud I run from the combiner box to the controllers..Run will be about 50 feet...#4awg wire? that what I was figuring thks Larry

The answer is on page 79.

Assuming you take my advice of a 5 x 3 and 5 x 2:

From the 5 x 3 array @ 50 feet will require a # 2 AWG minimum (36 amps)
From the 5 x 2 array @ 50 feet will require a # 4 AWG minimum (24 amps)

To make it easier and less complicated just use #2 AWG for both.

[larrybc1]

Larry for one it was a trick question because no matter what answer you gave, it would be the wrong answer, it will not work for 2 reasons.

1. You are using 12 volt panels on a 48 volt battery system. With just 3 panels in series can only be used on 12, 24, and 36 volt systems, not 48 volts. You need a minimum of 4 panels in series. Read page 76 of the owners manual. Minimum Vmp voltage must be equal to or greater than 60 volts. With 3 panels in series only gets you 55 volts. The FM-80 is a BUCK controller which means it can only down convert voltage, not up.

2. Each charge controller needs its own dedicated panel system. You cannot combine two systems on the inputs. You can however parallel the outputs to a common battery . So YES is the answer to your question. You will need 2 combiners and will have to loose at least 1 panel. Make both systems EQUAL in power or identical.

On second thought you can run two systems of 5 x 3 and 5 x 2.

Hi Derek..Yes I plan to have 2 systems--5x3 and 5x2 for a total of 25 panels..Voltage shud be VOC of 22.8 x 5 =114..That shud be OK?
So I guess i will have to get another MNPV-3 combiner box...thiks Larry

[Sunking]

Hi Derek..Yes I plan to have 2 systems--5x3 and 5x2 for a total of 25 panels..Voltage shud be VOC of 22.8 x 5 =114..That shud be OK?

OK my bad I thought you said 3 x 5, and 2 x 5. Anyway yes that will work, but for calculating the operating voltage you would use the Vmp of 91 volts. Voc is used to determine cold weather voltages by using a multiplier. Unless you get to 30 below 0 you should be OK

So I guess i will have to get another MNPV-3 combiner box...thiks Larry

Yep

[larrybc1]

OK my bad I thought you said 3 x 5, and 2 x 5. Anyway yes that will work, but for calculating the operating voltage you would use the Vmp of 91 volts. Voc is used to determine cold weather voltages by using a multiplier. Unless you get to 30 below 0 you should be OK



Yep

thks...Larry