12kw growatt inverter install

[godsglory22]

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.

Man your smart!.amazing. so I have 100 feet between my combiner box and the inverter location. 10 gauge will work?

 

[Kornbread]

Yes, me n math ... I probably made some mistakes ... YMMV.

2s9p. (2panels with a Vmp of 38.3 = 76.6volts 2panels in series with an Imp of 10.19 still = 10.19amps) Since you will have 4 strings on one mppt input, and 5 strings on the other mppt input, it should look something like 10.19amps per string x 4 strings = 40.76amps, or somewhere there abouts. The other side of the mppt input has 5strings x 10.19amps = 50.95amps on the other mppt input. This is ~ 7100watts, the panels maximum yield.

40.76amps on the string of 4
50.95amps on the string of 5

This is 6gauge copper at ~77v, ~51amps and 100' (200' round trip). Generally, most people try to keep voltage drop <3%. both calcs are giving approximately the same results. See 10gauge at ~14% ...

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This is 4gauge copper wire at ~77v, ~51amps and 100' (200' round trip). Still >3% but 4gauge copper is going to be expensive and it only gets worse as size increases. 1) This is pretty close, 2)more than likely, you are only going to make max power for a short amount of time, and 3)the cost vs benefit is only going to get worse.


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2-2-4 is a common size aluminium service entrance cable. Locally, it is ~$2.50per foot, while 4gauge copper is $1.57per foot. 100ft of 2-2-4 =~$250 while 200ft of copper #4 =~$314. Both will serve the purpose but copper is a bit easier to run, and apparently copper has decreased considerably since the last time I priced it. Anyhow, since you will have 2home runs, it's going to cost you at least~$500 for those runs, not counting conduit or trenching. This is probably the largest reason many people prefer solar charge controllers that accept high pv voltages. If your charge controller could accept 400v from pv, that same 7100watts would only have to push 17.75amps of current and require 14gauge copper wire. You can buy 500ft of copper thhn wire for $70.

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[godsglory22]

Do I need to rewire the combiner because it's pre-wired 3 and 3, so would I just move over the pv wire on the bus bar? I don't think you can because of the negative,positive coming out right?
That's what I'm tripped up on, combiner box, I've got 6 + & 6 -, arrays, but box doesn't allow for a 2-4?

 

[Nobodybusiness]

I have (18) 395w Canadian biracial panels.

I would like to see those. ?

 

[godsglory22]

I think I just figured it out, growatt can only take 7000w, my 18 (390) w 6 array will be too much,
If I just remove 1 390w from 1 array, wire all in series, that will give me 3120w on 1 input & 3510w on the other, with a total of 60 amps, and 6630w, based on growatt specs, am I correct lol, I'm a mother of 6 with no college lol and trying to do this alone

 

[Kornbread]

3panels in series are (voc of 48.6volts)146volts, you will be at the max allowable array open circuit voltage, until the weather cools off, then you will be over the max allowable pv open circuit voltage. These inverters do not like to be ran at or over their max pv voltage limit! However, overpaneling by a couple hundred watts is generally not an issue. About the only way you can safely configure those panels is with 2in a series, with 9total strings (2s9p). You will need another combiner box for 9strings.

 

[automatikdonn]

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

Well I showed you the math, you just have to look at your datasheet and plug in your numbers.

Good catch @Kornbread

 

[godsglory22]

What do you mean until the weather cools off? And when you say 9 in parallel, what do you mean 9 parallel and 2s, with 18 paneks how many on each array? 2 per arrays?

 

[automatikdonn]

What do you mean until the weather cools off? And when you say 9 in parallel, what do you mean 9 parallel and 2s, with 18 paneks how many on each array? 2 per arrays?

When it gets cold, the voltage of the panels will rise. Standard practice is to calculate the maximum voltage of the string by taking your VOC of the string in total and multiply by 1.25

You want to be 100% sure that you will never be over the maximum voltage of your MPPT, unless you like to cook electronics.

46.3 * 2s = 92.6 * 1.25 = 115.75v

If you were to use 3s it would look like this
46.3 * 3s = 139.14 * 1.25 = 173.975v

This is 23ish volts over the max allowed by your MPPT and could fry it. Hope this helps.

 

[MrM1]

I'm installing this same inverter in a Cargo Trailer. Got all my diagrams, pics and a few videos in this thread I did. Might help your build.

Off Grid Farm ~ Mobile Power Cargo Trailer Build: Growatt 12kw Install

Installing The Big Growatt SPF 12000T 12kw Inverter into a Cargo Trailer for a 12k watt mobile power generator. All the panels will be installed on a pole/post barn and I will connect the Inverter's Solar Charge Controller MPPT to the panels via 8 awg SOOW cable and Anderson Connectors. First...

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