12kw growatt inverter install

[godsglory22]

As I read every one's q & a's I'm quite intimidated. I have no knowledge and only learning online. I bought the growatt 12kw split phase off grid. I have (18) 395w Canadian biracial panels. How should I arrange the solar arrays? I thought at first an array couldn't exceed 1200w, after reading thru these threads, I'm now questioning everything I thought I had set up. I have a 6 array combiner box the arrays will feed too. Planned to do 6 arrays at 3 panels each. Also does it matter if the panels are connected in series or parallel when using growatt? I planned to connect positive to negative in each array.
I havnt actually ran everything and still installing it all.
Also the gauge of wire running from my combiner box, 6g or 10g? Also conflicting answers I've received. Thank you and any suggestions is more than I have right now now.

 

[automatikdonn]

There are a couple models of Growatt 12K inverters and they have different specs for Solar input. Can you share the exact model you have?

 

[godsglory22]

It the SPF 12000t dvm
GROWATT

 

[automatikdonn]

Here is the spec sheet I will reference from - https://signaturesolar.com/content/documents/GROWATT/1519004-specs.pdf
7000w Solar Input Maximum Total
150VDC

I don't know anything about your panels, so you need to do this math based on what the labels say. Lets use a value of 48v's per panel

First let start with the maximum input for your MPPT chargers.

7000w / 2 = 3500w maximum for each input

3500 / 385 = 9 panel MAXIMUM
150v / 48v = 3 panel MAXIMUM

What this means is we hit the voltage open circuit max before we hit the wattage max - so base your system on this basic set of principals.

You have 18 panels
18 / 3 = 6 (this is the number of parallel strings that will come into the combiner)

Next we take the VOC (voltage open circuit) and divide the total number of watts to get our amp load
18 panels * 395w = 7110w

7110 / 144v (48v x3) = 49.375a

So you should end up with a total amp load of 50 amps of actual current. Following a general rule of thumb, you would want to make sure you size your conductors to be at no more than 80% load. This means plan for a 60 amp circuit.
If you connect 3 panels in series and then parallel them into a combiner. You would end up with 6 total strings and you would need to split those over the two mppt inputs on the inverter.

YOU NEED TO GET THE VOC NUMBER FROM YOUR PANELS - Sorry to yell here - but its crazy important - these numbers could vary wildly with even a small change.

Also I am NOT a professional - my math could be wrong here (and I won't be ashamed if someone corrects me). This part is very important to get right, because if you don't.. well fire..

 

[godsglory22]

Ok I'll get this from the panel tomorrow. What confused me tho is how to do what you said, I understand I'll have the 6 arrays, but how do I split them into the 6?, with some being parallel and some being in series? Or can each array have panel a.d series wired? Yes I've watched videos, read, called, I thought I understood, I planned to just do 6 sets of 3 each? But growatt inverter seemed to telle that's not right?

 

[Darren67-72]

Your going to want to puke when you see the price of that wire.
Hang in there!!! One step at a time and it will all come together.
As for automatikdonn, my hats off to you for taking the time to help!!!

 

[godsglory22]

 

[godsglory22]

Here is the spec sheet I will reference from - https://signaturesolar.com/content/documents/GROWATT/1519004-specs.pdf
7000w Solar Input Maximum Total
150VDC

I don't know anything about your panels, so you need to do this math based on what the labels say. Lets use a value of 48v's per panel

First let start with the maximum input for your MPPT chargers.

7000w / 2 = 3500w maximum for each input

3500 / 385 = 9 panel MAXIMUM
150v / 48v = 3 panel MAXIMUM

What this means is we hit the voltage open circuit max before we hit the wattage max - so base your system on this basic set of principals.

You have 18 panels
18 / 3 = 6 (this is the number of parallel strings that will come into the combiner)

Next we take the VOC (voltage open circuit) and divide the total number of watts to get our amp load
18 panels * 395w = 7110w

7110 / 144v (48v x3) = 49.375a

So you should end up with a total amp load of 50 amps of actual current. Following a general rule of thumb, you would want to make sure you size your conductors to be at no more than 80% load. This means plan for a 60 amp circuit.
If you connect 3 panels in series and then parallel them into a combiner. You would end up with 6 total strings and you would need to split those over the two mppt inputs on the inverter.

YOU NEED TO GET THE VOC NUMBER FROM YOUR PANELS - Sorry to yell here - but its crazy important - these numbers could vary wildly with even a small change.

Also I am NOT a professional - my math could be wrong here (and I won't be ashamed if someone corrects me). This part is very important to get right, because if you don't.. well fire..

Got the panel info. Again dumby here, but how do I combine the 3 series and parallel In combiner, a sketch as the language sometes is french.but when I see it helps.

 

[godsglory22]

Your going to want to puke when you see the price of that wire.
Hang in there!!! One step at a time and it will all come together.
As for automatikdonn, my hats off to you for taking the time to help!!!

So my 18 panels are 390w and 48v, how do I arrange my arrays? I have a size 6 combiner box

 

[automatikdonn]

Got the panel info. Again dumby here, but how do I combine the 3 series and parallel In combiner, a sketch as the language sometes is french.but when I see it helps.

Here is the answer to your question

6-2 Solar Panel Combiner Box -(3 into 1 twice)- (2 x 63A max output) – Watts247 Wholesale

watts247.com

 

[justoneguy]

for wiring your panels to the combiner box,
6 arrays at 3 panels each. connect positive to negative in each array.
then connect 3 arrays positive to positive neg - neg.
do this twice.
that growatt has 2 mppt connections for this
30 amps is the limit for standard 10 gauge solar wire
3 x 10.74 amp is just over.
you'll probably never see 10.74 amp per panel but you may want to oversize the wire for distance and future expasion

 

[automatikdonn]

for wiring your panels to the combiner box,
6 arrays at 3 panels each. connect positive to negative in each array.
then connect 3 arrays positive to positive neg - neg.
do this twice.
that growatt has 2 mppt connections for this
30 amps is the limit for standard 10 gauge solar wire
3 x 10.74 amp is just over.
you'll probably never see 10.74 amp per panel but you may want to oversize the wire for distance and future expasion

Well that 30 amp rating doesn't cover the 80% rule, so it's more like a 30amp circuit is good for 24 amps(ish)

 

[godsglory22]

Well that 30 amp rating doesn't cover the 80% rule, so it's more like a 30amp circuit is good for 24 amps(ish)

What does this mean about the 39qmp, what can I do?

 

[godsglory22]

for wiring your panels to the combiner box,
6 arrays at 3 panels each. connect positive to negative in each array.
then connect 3 arrays positive to positive neg - neg.
do this twice.
that growatt has 2 mppt connections for this
30 amps is the limit for standard 10 gauge solar wire
3 x 10.74 amp is just over.
you'll probably never see 10.74 amp per panel but you may want to oversize the wire for distance and future expasion

But if I end up with only 2 arrays, I'm only inputting 2 to the 6 possible on the combiner box? I already.have the 6-2 box, is this ok? To still use it?

 

[godsglory22]

Here is the answer to your question

6-2 Solar Panel Combiner Box -(3 into 1 twice)- (2 x 63A max output) – Watts247 Wholesale

watts247.com

if I end up with only 2 arrays, I'm only inputting 2 to the 6 possible on the combiner box? I already.have the 6-2 box, is this ok? To still use it the 6-2 combiner ? Only using 2 ins?

 

[Panamon_Creel]

if I end up with only 2 arrays, I'm only inputting 2 to the 6 possible on the combiner box? I already.have the 6-2 box, is this ok? To still use it the 6-2 combiner ? Only using 2 ins?

If you look at the diagram in the fotos from the Watts247 6-2 combiner box then you see exactly how you should connect your 18 panels. 6 sets of 3 panel strings with each string connected individually to the combiner box which then will parallel 3 of those strings for each of the two PV inputs of the inverter.

 

[Kornbread]

Um ... the Voc on those panels is 46.8v. 46.8vx3 panels in series=140.4v(.2 cold coef.)=28.08v+140.4v=168.48Voc. If this is the spfxxxxt dvm non-us version (150v max pv input) a cool crisp day may leave things a bit smokey.

 

[godsglory22]

Um ... the Voc on those panels is 46.8v. 46.8vx3 panels in series=140.4v(.2 cold coef.)=28.08v+140.4v=168.48Voc. If this is the spfxxxxt dvm non-us version (150v max pv input) a cool crisp day may leave things a bit smokey.

Yes thank you this is what I've been asking and confused as to how to wire it to get the max but not blow.the 150, so far your the only one to write what I couldn't put in words myself lol

 

[Kornbread]

General rule of thumb, pick Voc of the panels so that however you wire them, the Voc is closer to the upper limit of the inverter's mppt operating range. Higher voltage will let you get away with smaller wire, and the mppt input is 'supposed' to be more efficient. You already have the panels, and the Voc/pv max v input, considering cold coef, would lead me to only having 2 panels in series 9 parallel strings. IIRC, the 12k has two pv inputs which is going to leave you with 4strings into one input and 5 strings into another input, but I don't really see an issue with that.

Since Vmp is around 38v, I'm thinking your going to see the mppt trying to keep the 2s panels around ~70'ish volts when making max power. My panels Vmp are 30.5v wired 3series, and when making max power the mppt likes to keep them around ~74'ish volts. With an Imp of ~10a per panel and a total amperage ~90amps, your wiring may get expensive. Two runs from pv array to mppt controller with 5strings on one side ~50amps per home run. Play around with this Voltage Drop Calc . Generally, you want to not have more than a 3% loss and as you can see, distance matters.

YMMV and since I'm typing this at 4am, subject to err.

 

[Kornbread]

Also, to keep the cost of the home runs down, you can use aluminum wire, but be mindful of terminations. I used what is commonly called triplex, or home service entrance cable. At the time, it was <$1per foot. Like everything, it's went up in price, but it's probably still much less than copper. It is a pain to run al through conduit.