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Solar Setup - Axpert


JannieM
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Good day, 

I have 30 Canadian Solar Panels, and 2 Axpert inverters connected in paralell, on the side of the inverter it sais, Min VOC 124V max VOC 450V, max current for Solar 18A, the solar panels is 300w canadian solar panels, 9 amps and 38 VOC, how should I connect the strings on the inverters, atm there are 3 strings per inverter 5 5 5 in serie and then in paralell, this would bring the amps to 27, wich is not right? 

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Hallo JannieM

Yes, it seems you have too many panels for the Inverters as far as my knowledge also. I use 12 x 360W Canadians in two strings of 6 in series and then in parallel and that keeps it at 4320 that is also just onder the 4.5kW limitation of the Mark 2's. Problems sneeks in with your 3rd sting of panels. 

Lets hear from the experts.

1692918951_Mark2specs.JPG.9be105348744ebc1e48b2927cc50caa6.JPG

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Hi Jannie

I have a similar setup, with the same 2 Axperts in parallel but only 20 panels (12 x 330W on the one and 8 x 360W on the other).

You can install your first set (array) as 7s+7s to the one inverter and the second set as 8s+8s to the second inverter. Then all 30 panels are utilised.
{This is, you parallel two series strings of 7 panels in set 1} 

The 2 sets do not have to be identical as they each go to their own MPPT charger, as long as the parallel strings are equal and you stay below the 450V.
The operating Voltage is lower than the stated Voc (Open Circuit V), so you may see a Voltage of less than 300V dc on the inverter for set 2.
The current source in both sets will then be 18Amp (max operating I).

Let us know please how it goes!
(you will notice how clever the Parallel configuration will utilise the power drawn from the 2 uneven PV sets)

Kind Regards
Jaco

PS: I did enquire my supplier in the past and Voltronic replied to say it is safe to over-design the PV by 20% that is 5400W (max!) on one inverter, however the Inverter will not draw more than 4500. You should be OK with 16 panels (4800W) in the second set..

Edited by Jaco P Bloem
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15 hours ago, Jaco P Bloem said:

Voltronic replied to say it is safe to over-design the PV by 20% that is 5400W (max!)

Interesting. Did Voltronic actually quote the 5400 W figure?

My understanding was that these models have a 4000 W nominal SCC (basically 80 A @ 50 V), and that 4500 W was the recommended maximum nominal array power.

So that's 4500/4000 x 100% = 112.5% or 12.5% "overclocking".

If they only mentioned the 20% figure then I believe it should be 120% x 4000 W, which is only 4800 W (as opposed to 120% x 4500 = 5400 W).

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Thanks @Coulomb, yes the Charge Capacity is given as 80Amp and Rated PV at 4500W. Voltronic qouted the 20% so my supplier wrote 5400W which made my eyebrows lift as well- I will rather agree with your Calc.

Fortunately @JannieM should still be OK with 16 panels (300W) in the second array giving 4800W. I think the point they are making is that the current drawn from the PV source will be limited to produce 4500W.

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