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connecting an odd number of panels

Azzur

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Jul 17, 2022
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how best to connect an odd number of panels 7x455kWp=3180kWp, Voc 49.5V, Isc 11.66A.
Azzurro 3000 converter 2xMPPT
Typical DC power 3300W
Maximum DC input voltage 600V
Nominal DC input voltage 360V
MPPT DC voltage range 50-570V
Maximum input current for each MPPT 12,5A
Maximum absolute current for each MPPT 15A
Start-up voltage 60V
DC voltage range at full load 125-520V

Thank you for your response
 
I don't want you to feel ignored... there are soooooo many ways. Everyone has a little different opinion on panel arrangements. Most are not wrong, just different.
I'll suggest to keep your panel, incoming voltage, safety below the mppt voltage. Account for winter cold spikes. It depend where your located.
Ok, it's a start. And odd numbers of panels, are not optimal.
Lastly, There is a ton of math in that question.
 
I chose an odd number because I want to use the maximum space.
Option number 1: string number 1 - 4 panels, string number 2 3 panels... the question is whether or not to select parallel operation on the inverter...
Option number: 2 connect the panels all in a row as one string and connect them via a Y piece to both MPPT.... The panels will be placed in a sunny place where there is no shading... by the eye of the clouds :).
Sorry for the translation...I'm working with a translator
 
Option 3 - Voc of 50v * 7 in series will get you:
350v @ 11amps. That is in the range of the SCC.

Don’t hook it up to both Mppt’s.

If later you get more panels- hook them to the second MPPT.
 
You need to look at MAX voc @ 600v for panels and max on mppt is 570v
Option 1 is better start.
Or potion 3... not #2
 
why is option number 2 worse compared to option number 3......the difference is only in the inclusion of the branching cable at the inverter....wouldn't the inverter be less loaded if it were divided into 2 inputs?
 
with this inverter, I probably can't connect more panels....Typical DC power 3300W....my panels 3180Wp....max power for chanel 3000W.....that's why I wouldn't connect everything to only one channel
 
Then option 1.

You don’t want to connect a string of panels to different mppt’s with a Y connection. They will fight and won’t figure out the maximum power point correctly.
 
this argument is very reasonable and explained many things to me. There is one more option, I can buy a stronger inverter where one input can handle 3500W. Then I would be able to connect only one string as you advised me. But I am troubled by the thought, whether the unnecessarily large 4600W inverter will not work in the wrong mode if "only" 3100Wp is connected there. Inverters do not work ideally at low loads, and the more powerful the inverter and the fewer panels, the worse the situation.
 
Don’t buy a bigger inverter than you may foreseeable need.

You can either go Option 1 - 2 strings of 4&3 panels or Option 3. Option 3 is called over-paneling. (Make sure it can handle it before you do it). Some SCC’s handle it - I have 800w of panels on a 700w SCC - mine can handle it.

I would go with Option 1 - if you ever decide to get more panels - figure out how you will change stuff up then.
 
282 / 5 000
thanks everyone for the good advice......one more question. You are telling me not to buy a stronger converter. I haven't bought an inverter yet, which is an advantage, the panels are already at home, so I was wondering if I should buy a stronger one....In the attachment is the inverter specification, I am deciding between 3000W and 4600W
 

Attachments

  • 22535_1150_22535_1149_22535_1148__ps_1147Datasheet-ZCS-1PH-3000-6000TLM-V3-EN--1.pdf
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OK. I can see your concern about 7 panels into 1 MPPT on the 3000 model.

I don’t personally believe it will be a problem but I’m not the one buying, installing and using. So if you would rather not do that then I see the following options if more PV panels are not feasible for you at this time (but it may be later):

i. 3000 inverter with 2 strings, 1 x 3 panels + 1 x 4 panels, each into it’s own separate MPPT.
This is within the operating specifications of that inverter
Do NOT parallel arrays with a different number of panels

ii. 3000 inverter with 1 string x 6 panels into 1 MPPT (not using one panel)

iii. 4600 inverter with 1 string x 7 panels into 1 MPPT

Option i. will work fine.
The string of 3 panels might take a little longer to “wake up” in the morning but it will be fine. 3 of those panels is enough voltage.

Option ii. will also work but you lose 1/7th of your possible production.
It does however leave a spare MPPT so you have the option to buy some extra panels and add a second string of at least 3 panels into the second MPPT. The second string can face a different direction or be in a different location.

Option iii. will mean you use all 7 panels and like option ii. it leaves a spare MPPT so you have the option to add a second PV string in a different location and orientation if you wish to expand and had suitable space.

Of course it may be a different inverter brand/model might be better suited for your PV array. So the above assumes you are set on that particular brand of inverter.

Which of those is suitable depends on your budget, your expected energy demand and how much PV output you want/need, local regulations on how much solar PV you are permitted to install, and whether you may wish to expand the system capacity in future and of course whether you have any space to do that.
 
Thanks for the good advice. I bought a model 4600 inverter, I will connect one string - 7 panels, as you advised me. Can the second string remain unconnected?
 
every mppt controller has a rating of 33% over rating. if you have a 3000 mppt rating your panels can send 3999. each 1000 gets you 1333. your inverter will only use the 3000 watts most likely. but on cloudy days that will be to your advantage. each of my inverts have 5k rating so I can do 6665 max pv watts. it will still only use from what I have seen 5100 watts. this is called over sizing your panels input so cloudy days you get more power into your batteries after loads are used.

Please stop. This is just wrong.
 
are you an idiot?
I'm not sunshine_eggo but they are not an idiot. You seem new here, so perhaps give some of the more experienced people some credit before calling them an idiot.

What you wrote is clearly incorrect. If you do not understand why then I suggest refraining from posting until you learn more about MPPTs and over panelling.

But for a start, there are many different MPPT systems and they each have quite variable specifications. You absolutely cannot assume adding 33% more panels than a nameplate MPPT rating is always possible.

There are a multitude of reasons for that but fundamentally people should simply refer to the specifications of their equipment.

if you have a 3000 mppt rating your panels can send 3999. each 1000 gets you 1333.
No, they won't.

If you do not understand why this is wrong, then again I suggest refraining from posting on such things until you understand how solar PV systems actually operate.
 
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