Hi Guys, newbie question for my string arrangement that will feed my Sunsynk 8kw

Due to my roof configuration and space,  I need to get crafty with my string arrangement. Can I install 2 strings of 6 x 550w panels each on one mppt and 2 strings of 3 x 550w panels on the other mppt?

Note that string 1 will face east and string 2 will face west, the same with string 3 and 4. Excuse my drawing below

Thank you in advance

 

I think the 8KW Sunsynk is a two MPPT inverter allowing 2x strings in parallel on each MPPT, but the specs are for the combined values of the strings on each MPPT and not for each string independently on an MPPT. (If this makes sense)

My five cents worth:

On both strings you will probably be borderline too high on PV input current and PV Short circuit current of the inverter at 22amp and 28amp respectively. 
The 550W PV's are around 13amp Imp/A and 14amp Isc/A. Thus, you could expect 26amp Imp/A and 28amp Isc/A when the PV strings are in parallel. (Ideal conditions)

String 3+4 PV Voltage would probably be too low for effective MPPT voltage range of 150Vdc - 400 Vdc.
The 550W PV's are around 49.9 Voc/V and 41.96 Vmp/V. Multiply by three would be marginal too low for MPPT's to run effectively.

Would you roof allow you to do 2x strings of 7x PV's each instead? Connected on each MPPT would put you well in operational specs.

Regards

Hi Gerald, thank you for the advice. Makes perfect sense

On 2023/05/18 at 5:31 PM, Gerald V said:

I think the 8KW Sunsynk is a two MPPT inverter allowing 2x strings in parallel on each MPPT, but the specs are for the combined values of the strings on each MPPT and not for each string independently on an MPPT. (If this makes sense)

My five cents worth:

On both strings you will probably be borderline too high on PV input current and PV Short circuit current of the inverter at 22amp and 28amp respectively. 
The 550W PV's are around 13amp Imp/A and 14amp Isc/A. Thus, you could expect 26amp Imp/A and 28amp Isc/A when the PV strings are in parallel. (Ideal conditions)

String 3+4 PV Voltage would probably be too low for effective MPPT voltage range of 150Vdc - 400 Vdc.
The 550W PV's are around 49.9 Voc/V and 41.96 Vmp/V. Multiply by three would be marginal too low for MPPT's to run effectively.

Would you roof allow you to do 2x strings of 7x PV's each instead? Connected on each MPPT would put you well in operational specs.

Regards

Which is most important for the 8kw Sunsynk, is it V or is it A? If Nick's drawings are directionally correct I would suggest that the 6s east, 6s west and then the remaining (3 + 3) combined to get 6s. So you will have max 300V and 11A per string.

It is best to have as high as possible V, while staying under preferably 450V. The higher V the faster the mppt starts up. 

You can go over on current, the inverter will only draw what it can use. You can not go over on voltage - over voltage will damage the inverter. Also remember that you need to reach minimum voltage to start up the MPPT. 

On 2023/05/18 at 5:31 PM, Gerald V said:

Would you roof allow you to do 2x strings of 7x PV's each instead? Connected on each MPPT would put you well in operational specs.

Even 8 should be okay. But in principle, 7 or 8 panels electrically in series into each MPPT. And each series pointing either East or West. Even if it gets complicated with where the panels are placed, if it's (6+2) + (6+2), that should be fine.

Interesting idea @NickCT

Sounds like string 1 & 2 setup may actually work without too large a loss in power. 

Found a whitepaper on it 🙂 

String 3 & 4 would be better to combine into a 1p6s setup to get the voltage up

east-west-solar-paper.pdf

Thank you all for the invaluable feedback. We installed 2 strings of 6x550w facing East and West respectively. Will monitor now and hopefully provide some feedback on the performance soon. We experienced cloudy (rainy) weather since installation. I must compliment the members on this group though, thank you for sharing your wisdom 

On 2023/06/01 at 11:40 AM, NickCT said:

Thank you all for the invaluable feedback. We installed 2 strings of 6x550w facing East and West respectively. Will monitor now and hopefully provide some feedback on the performance soon. We experienced cloudy (rainy) weather since installation. I must compliment the members on this group though, thank you for sharing your wisdom 

Nick, what did you do with the remaining 6 panels? What is your current voltage while the sun is shining? Does the 8kw inverter show 4 different voltages or only 2?

1 hour ago, Vaal said:

Nick, what did you do with the remaining 6 panels? What is your current voltage while the sun is shining? Does the 8kw inverter show 4 different voltages or only 2?

There should be only 2 as 1&2 are in parallel on the inverter terminals and the same for 3&4. It remains 2 x MPPTs. 

8 minutes ago, Scorp007 said:

There should be only 2 as 1&2 are in parallel on the inverter terminals and the same for 3&4. It remains 2 x MPPTs. 

Thanks

Can anyone help me i have inifinisolar VII-5KW n pylontech up5000 48volts but I can’t make them communicate. Help 

On 2023/05/31 at 10:41 PM, Sc00bs said:

Interesting idea @NickCT

Sounds like string 1 & 2 setup may actually work without too large a loss in power. 

Found a whitepaper on it 🙂 

String 3 & 4 would be better to combine into a 1p6s setup to get the voltage up

east-west-solar-paper.pdf 172.28 kB · 14 downloads

That is correct, the 6 x E & 6 x W arrangement will work fine, the panels will start producing earlier and stay on longer than the true N orientation.

Winter time is not the best time to monitor their performance.

A very stimulating debate this (above). So, help me out please forumites, if I get a total of 20 x 550w Solar Panels and have a:

• North-Eastern Facing Face roof = 10 x 550W panels on Mppt-1
• South-Western Facing roof = 10 x 550W panels on Mppt-2

...are we saying my 8kW Sunsynk Inverter may actually during sunrise run on Mppt-1, ONLY  (North-Western) until say around 10am when the South-Western Mppt-2 begins to get some solar too and then at sundown, Mppt-2 because it continues to receive solar for longer, run on it's own and this will be ok for my system? See diagram (pic insert).

15 minutes ago, Moffat said:

A very stimulating debate this (above). So, help me out please forumites, if I get a total of 20 x 550w Solar Panels and have a:

• North-Eastern Facing Face roof = 10 x 550W panels on Mppt-1
• South-Western Facing roof = 10 x 550W panels on Mppt-2

...are we saying my 8kW Sunsynk Inverter may actually during sunrise run on Mppt-1, ONLY  (North-Western) until say around 10am when the South-Western Mppt-2 begins to get some solar too and then at sundown, Mppt-2 because it continues to receive solar for longer, run on it's own and this will be ok for my system? See diagram (pic insert).

Initially 10 per MPPT seems to have a too high Voc. To confirm indicate which province and also the specs of the panels or at least the make and model. 

Is there a reason why you can't fit the S-W panels also N-E to the right of the proposed N-E string of 10?

32 minutes ago, Scorp007 said:

Initially 10 per MPPT seems to have a too high Voc. To confirm indicate which province and also the specs of the panels or at least the make and model. 

Is there a reason why you can't fit the S-W panels also N-E to the right of the proposed N-E string of 10?

I'm unable to fit all panels on one side because I also have a 200litre solar geyser on the roof and maximum I can fit after the solar geyser would be only 2-panels. Current system has 12 x 250w panels (all on the N-E side). The 250W panels are smaller and I didn't want to put 12 x 550w as I would lose out on producing more PV and having inverter to fully charge my batteries faster. The other area, belongs to someone else since I live on a block of flats so the roof is not mine. The maximum PV for the 8Kw Sunsynk Hybrid Inverter is stated as 10,400w. I thought about that yes 10 panels per Mppt may be too much as well so maybe I put 8 on each side. In winter when it's not so hot and the sky is clear in Harare, Zimbabwe, the inverter is then likely to produce a lot more PV. See amended pic.

33 minutes ago, Moffat said:

I'm unable to fit all panels on one side because I also have a 200litre solar geyser on the roof and maximum I can fit after the solar geyser would be only 2-panels. Current system has 12 x 250w panels (all on the N-E side). The 250W panels are smaller and I didn't want to put 12 x 550w as I would lose out on producing more PV and having inverter to fully charge my batteries faster. The other area, belongs to someone else since I live on a block of flats so the roof is not mine. The maximum PV for the 8Kw Sunsynk Hybrid Inverter is stated as 10,400w. I thought about that yes 10 panels per Mppt may be too much as well so maybe I put 8 on each side. In winter when it's not so hot and the sky is clear in Harare, Zimbabwe, the inverter is then likely to produce a lot more PV. See amended pic.

If the panels used have a Voc of about 50V you might be able to fit 9 panels instead of 8 per string to provide a bit more PV. 

29 minutes ago, Scorp007 said:

If the panels used have a Voc of about 50V you might be able to fit 9 panels instead of 8 per string to provide a bit more PV. 

Will look at the the VoC and see how to work it out. Adding panels, even later is always cheaper, than the battery bank "punishing prices"😢

What about the section in blue below? Is that your roof or the neighbour's? it points almost straight Northwards if I'm reading the compass right, so it would better than a West or East-facing roof, generating around 10-15% more power throughout the day.

With that, would it make sense to fit 9x550 panels facing North, and in any case just keep the 12x250 panels facing East (panel voltages to be checked, but I'm asssuming around 50Voc for the 550W panels, and around 38Voc for the 250W panels, in each case summing to around 450V in series? Or a total of just about 8kW, and you could always decide to replace the panels entirely on the East side if you really need more power later.

I think those roof sections should mostly be out of sight of each other, so the visual mismatch might not be an issue.

 

Edited October 18, 20232 yr by GreenFields

5 minutes ago, GreenFields said:

What about the section in blue below? Is that your roof or the neighbour's? it points almost straight Northwards if I'm reading the compass right, so it would better than a West or East-facing roof, generating around 10-15% more power throughout the day.

With that, would it make sense to fit 9x550 panels facing North, and in any case just keep the 12x250 panels facing East (panel voltages to be checked, but I'm asssuming around 50Voc for the 550W panels, and around 38Voc for the 250W panels, in each case summing to around 450V in series? Or a total of just about 8kW, and you could always decide to add more panels on the East side if you really need to later.

I think those roof sections should mostly be out of sight of each other, so the visual mismatch might not be an issue.

 

I am still using 6x270W panels and I had the same idea you mentioned about the 12x250W panels. 

The blue part is my roof but would need to check how much shading happens on that side of the property in the winter. What I do know is that at this time of year I get a lot of sunshine onto that part of roof and the shading from neighbours in the very late afternoon. Not sure what specs my 250w panels are because another option would be to buy:

18 x 555w panels and split them as:

• Mppt-1 = 9
• Mppt-2 = 9

The older 250w are old at .9% or even less efficiency would be delivering 2,700w, which I can then donate to someone else with the old inverter as well as the battery too. I know during the day, at least the old "Chinese-knock-off" inverter still produces adequate power to run literally my whole load:

• 0.5hp water pump
• 1 x Upright fridge
• 1 x Chest freezer
• 2000w Induction cooktop (can make a cup of tea or a meal) so someone will make good use of it during the day. If they get a 200ah lithium battery, then they can run with lights all night.

I've updated the angle, to give a more accurate view of the whole plan. Only issue is blue part gets sun much later as the roof slopes up and it's shaded in the morning, but will give it a good look in the morning. Too many parameters to consider. The other issue is the blue part means longer DC cable to the Inverter marked by the X in green as well. Too many permutations this solar business.

 

On 2023/10/18 at 10:30 PM, GreenFields said:

What about the section in blue below? Is that your roof or the neighbour's? it points almost straight Northwards if I'm reading the compass right, so it would better than a West or East-facing roof, generating around 10-15% more power throughout the day.

With that, would it make sense to fit 9x550 panels facing North, and in any case just keep the 12x250 panels facing East (panel voltages to be checked, but I'm asssuming around 50Voc for the 550W panels, and around 38Voc for the 250W panels, in each case summing to around 450V in series? Or a total of just about 8kW, and you could always decide to replace the panels entirely on the East side if you really need more power later.

I think those roof sections should mostly be out of sight of each other, so the visual mismatch might not be an issue.

 

Sorry had gone awol for a bit, I did check if the blue part I can put panels, the answer is yes, though not advisable as I have trees shading the roof from about 3pm, which would affect production prematurely, so it looks like I'm stuck with areas A & B, with my other challenge now being that I realize that 550w panels are quite big. The current 12 x 250 panels were fitting because they are physically smaller...