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Panel Layout

Copperman

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Kansas
Want to make sure I understand this correctly, as I want to minimize the trips my old arse has to be on the slick metal roof...lol

I'm doing an off-grid 30 X 50 storage building, using a Growatt 3000 48V inverter with 4 renogy 12V cells wired in series. No AC input. I have 4 VSUN455-144BMH Bifacial Panels, which are rated at 49V OCV / 41V Max @ 455Watts. My plan is to group the 4 panels by doing two groups of 2 panels in series, and then joining both of those groups in parallel. The cold start voltage on the Growatt is 46V, so I figure I will need to pair them to bring the voltage up and the wattage should be good as well. or am I missing something here?
 
The 46V of the Growatt is the BATTERY voltage, not the voltage of the solar string. You really need to be doing more extensive research into this brefore starting purchases! The solar input has a higher requirement. Here are the cut & pasted specifications for Growatt's 3000W inverter.
1695936283257.png

I had trouble finding the actual specifications for those panels, but let's assume the Vmp is ~41V. Three is series MIGHT barely reach 123VDC in the spring or fall, but maybe drop below 120V in the middle of summer while on a hot roof. Four in series should be about 160V or so, safely in the lower mid range of 120-250VDC. Four in series is the only viable choice.
 
If you are using the VSUN455-144BMH panels and the specs above are correct for you growatt inverter, 4 of these panels in series will work. 4 in series are needed to get enough volts to hit the minimum volt, also you will want no more then 4 in series to not exceed the 250volt limit in cold weather.
 
The 46V of the Growatt is the BATTERY voltage, not the voltage of the solar string. You really need to be doing more extensive research into this brefore starting purchases! The solar input has a higher requirement. Here are the cut & pasted specifications for Growatt's 3000W inverter.
View attachment 169944

I had trouble finding the actual specifications for those panels, but let's assume the Vmp is ~41V. Three is series MIGHT barely reach 123VDC in the spring or fall, but maybe drop below 120V in the middle of summer while on a hot roof. Four in series should be about 160V or so, safely in the lower mid range of 120-250VDC. Four in series is the only viable choice.
I appreciate the info, but with all due respect, I did do a lot of research, and the panels were not purchased, they were given to me in trade by an individual that bought several lots at an auction for a solar company that went out of business a couple of months ago in KCMO (he just wanted the tools). This project is pretty much a bag of mis-matched stuff from that truckload of parts, and you are correct, the Vmp is 41.40V. The only parts of this I spent any real money on was the Growatt and the batteries. I started this project and was looking at buying all of the various parts when this opportunity came out of a conversation I had with a friend of a friend about buying panels and how expensive shipping was. He made a call and in a day, I had a pickup load of boxes he no longer wanted to deal with. I do understand the concept of the array, I just mis-understood the requirements for the inverter....this is why I came here to learn. The panels might not be optimal, but they are what was available, and the price was right. As part of that deal, I'll have several boxes of new aluminum mounts, L-feet, and an entire tub of new stainless bolts, nuts and leftover hardware I'll offer up for very minimal cost to help out other newbies once this project is done. Much of it is still in the Fastenal bags. There are several boxes I haven't even looked in yet.
 
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If you are using the VSUN455-144BMH panels and the specs above are correct for you growatt inverter, 4 of these panels in series will work. 4 in series are needed to get enough volts to hit the minimum volt, also you will want no more then 4 in series to not exceed the 250volt limit in cold weather.
Thanks, now that I understand what I was looking at, it makes sense.
 
Guys, I think I got some bad advice here, and if so, this is going to be a big problem. I felt like an idiot for my plan to group two sets of panels in series, and based on what I was told above, I installed all 4 panels in series and am producing 176 VDC. That might sound great, but I went back to the Growatt site and looked up the inverter I am installing, and the specs do not match what is listed above. Yes, I should have argued this, but I figured I had missed something in my calculation, and the more I look at it, the more I think you were looking at a different inverter. The inverter I am using is SPF3000TL LVM......and the spec sheet I am looking at, is not the same as what is listed above. This shows the MPPT operating range of 60V-115V DC. Where did the specs above come from? Had I installed like I originally planned, I would be at 88VDC.....but I am at 176. I cannot pull those panels back up, it was a 2-day project on a hot tin roof with a boom lift to get them installed, but I don't think this is going to be compaible. @MichaelK

1696218593254.png
 
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I mean without pulling them off the roof. Solar installers rewire under panels while servicing. EDIT: in teams of two or three

For me It’s doable solo on my 25 degree composition roof
 
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You have at least a couple of choices: 1) rewire your panels to match the inverter you have, 2) get an inverter that matches the specifications of the panels you have as they are wired.

I suppose you could get a standalone charge controller that works with your panels as they are wired and ignore the growatt PV input (but that sort of defeats the purpose of an all-in-one.)

Lesson learned? RTFM.
 
Nope, high pitch slick metal roof. It takes a boom to keep them from sliding off

Yikes. Take your pick between renting boom, hiring solar service, or buying new AIO and eBay the other one

Since this kind of setup is high consequence for error and it is your first time doing solar it may be advisable to wire up on the ground as bench testing first
 
Yikes. Take your pick between renting boom, hiring solar service, or buying new AIO and eBay the other one

Since this kind of setup is high consequence for error and it is your first time doing solar it may be advisable to wire up on the ground as bench testing first
There was nothing wrong with the original plan. I had it right from the beginning, but when I started asking for advice, I got into trouble. It's obvious this isn't going to work now that the panels are set, so I am looking at either a charge controller or a different inverter. Raising the panels is not a viable option as it is too time and labor consuming. Thanks .....
 
Thanks...things happen. I shouldn't have second guessed myself. I'm working on a new inverter. Should be here next week.
 

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