DEYE SUN-8K-SG01LP1-EU wiring to PV string

[Propalen]

Hi there,

I have a couple of doubts regarding the wiring for the SUN-8K-SG01LP1-EU inverter.

These are the specs for this inverter regarding PV string input



I am intending to connect 18 panels. Since there are 3 panels affected by morning shadow and the other 3 affected by afternoon shadow, I thought to connect two strings of 6 panels and two strings of 3 panels. Here are the specs of the panels to be used:

My doubts are:

1) The inverter MPTT volftage range indicates 150 to 425. On the 6 panel strings is safe (298,8v), but on the 3 panel strings is under the below the indicated range (149.4v). Would that be a problem? Should be a minumum of 4 panels for each string?

2) The PC invput current is indicated at 26+26A. So I presume that this 26A per MPTT tracker, and 13A per string. The panles indicate a current of 13.12A. Could that be a problem?

3) Could you forsee any other problem with this configuration?

Many thanks!

 

[RP67]

I have the same inverter for a year now, and I also have a similar panel positioning. NE 14 panels and SW 6 panels. What I found interesting, one MPPT is only goes up to 20A, regardless. I have 440W Jinko panels, and I ended up to connect 8 of the 14 to MPPT1 and the rest of them to MPPT2 with the other 6 (two strings). In my case the min V is not an issue, but when I kept the 14 panels on the same MPPT the 20 A reduced my generation in a good part of the day. Now I have a small loss due to the split facing, but the sum generation is way better than before.
I would go for 6+3/ MPPT to see how it performs. I guess you will get the four string DC wiring down to the inverter, which will be easy enough to change over if you want to.

 

[Propalen]

@RP67 Thanks for your reply.

I think I need to get the nb of panels per string right first ... My roof is not so accessible so I need to hire an elevator. According to your comments, my only doubt is if a string of 3 panels will be ok. My options now are 6+3/MPPT or 5+4/MPPT. Due to shadow conditions if 3 panels are ok, then 6+3/MPPT will be the optimal solution. Can anyone help how the minimum voltage range affects the production?

btw @RP67 how did you find out that one of your MPPT was going only up to 20A? Specs indicate 26+26

 

[RP67]

The number of panels per MPPT is summed, therefore the minimum voltage is always met the requirement. So if you do 6+3, it is 9 ( OK, just like 5+4), but you keep separate the string of 3, which is in shade some part of the day (on each MPPT). So you maximize the generation through the day.
If the minimum voltage is not met, the inverter simply will not start to generate (as far I understand). Once is up to the minimum, it will start to generate on the panels current rating. A will fluctuates as the sun exposure changes (light cloud etc).

I simply checked the historical data... my inverter data table says 22A per MPPT (28A Isc), and I expected to getting close to 22A. I guess that is same sort of "safety margin". Don't forget it is Chinese made. Considering that, it works very well, I have close to none issues with the performance/quality.

 

[Propalen]

@RP67 Truly thanks for uploading this picture. I presume that the same applies to the current. Let me explain. If I connect 6+3, the current will not be summed as in parallel, 13A+13A (26A), but they will be as in series so the MPTT will only receive 13A. 13A will well under the specs (22A) but 26A will be over. That's my last concern. Thanks!

 

[RP67]

will your 6 and 3 panel string run on full capacity at any part of the day/year?

 

[Propalen]

Not sure. Maybe on summer they could reach 90% yield. I presume the current only reaches 13A once in full production capacity. Is that correct?