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Sol-Ark 15k and Sunpower X21-335 panel placement on East/West arrays

Braebyrn

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Feb 2, 2020
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I have recently installed a Sol-Ark 15k inverter and temporarily installed 20 Sunpower X21-335w panels. 15 panels on my pergola and 5 propped up towards the afternoon sun. This is temporary as I don't know the rules for pergolas and was excited to see the 15k function and the old roof issue.

My roof is 24 years old and has a few areas that look like its loosing the granules at a higher rate. So the roof will need to be replaced before I put the new panels on the roof. Meanwhile, I was hoping to get some advice on the placement of the panels after the roof is installed.

The Sol-Ark 15k has three MPPT inputs. My house is pretty much East/West facing. I can use 3 strings of 6 per MPPT. So 18 panels per MPPT. I have only 40 panels right now, and also limited to the roof and pergola space. I could use the 3rd MPPT on the 3rd MPPT.

I also have 40 Tigo TS4-A-O units to tie in with the panels.

How would I string these panels on my roof? Attached are a couple of placement attempts. But with east/west facing, it is probably not a good idea to have the three south facing panels on the plans.

Any help would greatly be appreciated.
 

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Thx for posting this, I am wondering the same thing. How does sol ark handle different voltages due to direction.

Are you going to be stuck using 2/3 power (east / west) and a tiny bit south on the 3rd mppt?

Support might have Answer on that.
 
The 15k has 3 MPPTs but each can accept 2 strings of different orientations. So you can have up to 6 strings. The catch is the 2 strings on the same MPPT input need to be the same voltage. Also the minimum voltage per string is 125.
 
The 15k has 3 MPPTs but each can accept 2 strings of different orientations. So you can have up to 6 strings. The catch is the 2 strings on the same MPPT input need to be the same voltage. Also the minimum voltage per string is 125.
^^^
Which means that for those panels (57v nominal), you want to make sure the lowest "expected" voltage on a string exceeds the 125v - so I'd guess somewhere in the 4-6 panels?
 
At least 3 panels in series if the Voc of each is 57v. The 15k handles up to 425v (bad things don't happen to the inverter until you hit 500v, but the 425v figure allows for some headroom in case panels run higher in low temperature etc). Higher voltages also trigger startup at lower light levels, and allow for smaller wires.
 
Sol ark support got back to me promptly.

Each of the 3 mppt inputs are seperate hardware and they function well unless you pass the max voltage or current.

I'd propose best results would come from stringing together panels only facing the same direction so voltage remains consistenr to that mppt when the sun is coming from that direction.

Of course that may not be as flexible as you desire.

In that case you could use the 3 mppt inputs for your main east west and south strings.

The left over small stuff you could ac couple on the generator input.
 
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