Don't do that. If you put 2 strings in parallel onto one MPPT, they should have the same Voltage, or close to. The two MPPTs don't each have to have the same amount of panels in total.

What's your roof configuration, and why are you considering this specific setup? What panels and inverter are you talking about? Specs &/or model numbers?

deye 20kw 3 phase

2 mppts plus 2 strings each. 850max V per mppt.

 

for max efficiency wanted to group orientations and roofs.

6 roofs.. 3 west and 3 east

west taking 7 plus 5 plus 5 (17) - propose 12 in line on 1 string plus 5 on string 2 (17) into 1 mppt.

east taking 5,5,5 panels (propose 10 on 1 string and 5 on other into 1 mppt)

545w panels, max v 49, 13.1 amps

 

 

 

 

 

deye 20kw 3 phase

2 mppts plus 2 strings each. 850max V per mppt.

 

for max efficiency wanted to group orientations and roofs.

6 roofs.. 3 west and 3 east

west taking 7 plus 5 plus 5 (17) - propose 12 in line on 1 string plus 5 on string 2 (17) into 1 mppt.

east taking 5,5,5 panels (propose 10 on 1 string and 5 on other into 1 mppt)

545w panels, max v 49, 13.1 amps

 

 

 

 

You're right in wanting to group the roof orientations together.

I'd suggest fewer panels, though, say for the West-facing panels, put 9+9 panels electrically in parallel instead of 17 if you can make space for 1 more, otherwise drop down to 8+8 in parallel, or even consider 15 panels in series onto MPPT1. Even if it makes for a strange split across different roofs.

Similarly, the East-facing panels should be okay with 5+5+5 all in series, then onto MPPT2.

Just a thought, to be verified by the installer for your setup. On the understanding that suitable PV cabling can be routed securely between the roof sections.

suggested strings in nrs and little lines indicate panels.

big arrow is north

 

 

will this solution work—, if we designed 4 strings, build a DC board to split them, we can split them before they connec to  the inverter. Your inverter will read and process only 2 strings, but we can wire all strings to a sub db before going to inverter

will this solution work—, if we designed 4 strings, build a DC board to split them, we can split them before they connec to  the inverter. Your inverter will read and process only 2 strings, but we can wire all strings to a sub db before going to inverter

 

some of the east and west panels will get sun longer, earlier or later so wanted to split as much.. possible to add external mppts. eg run 6 mppts. 1 for each roof?

I don't want to hijack this thread but I am also struggling with the whole Voc / Isc and ensuring the panels are wired up to optimise their performance. I have a 16kW Deye and 30 Jinko 560N panels. The specs for the Deye are as below with 3 MPPT’s and two strings per MPPT and the panel specs are Voc 50.47V, Isc 14.14A and Pmax 560W at STC.

I am in Cape Town and the panels are installed on two separate roofs which are both next to each other and face the same direction which is pretty much North and are at the same angle. They are installed as 5 X 4 = 20 and 5 X 2 =10 panels. So 20 panels on the one roof and 10 on the other.

I think the installer has put the panels up as 3 serialised strings of 10 panels to each MPPT. I have seen Voltages of 504V – 508V on the PV side when the load has decreased and it is midday and I really don’t want to cook this thing !

So my matchbox calculation, with very limited knowledge which is always a dangerous combination,  is at Zero degrees temperature Voc will increase to approximately 55.52V per panel (about a 10% uplift), meaning 555V per MPPT which can fry the MPPT’s.

The way I understand it is that to keep the MPPT as happy and efficient as possible you want to try and limit the voltage to a maximum of 425V as it’s range is 150 -425V ?

So what would be the best / most optimal way to connect the 30 panels to the Inverter ? 6 strings of 5 panels in each string ? That is only around 275 Volts though, is it better to run it higher ? Where does the Isc play a role in the calculations ?

Any input would be greatly appreciated !

Thanks, Grant.

PV String Input Data
Max. DC Input Power (W)			20800
Max. DC Input Voltage (V)	500
Start-up Voltage (V)	125
MPPT Range (V)	150~425
Rated DC Input Voltage (V)	370
PV Input Current (A)	26+26+26
Max. PV ISC (A)	44+44+44
No.of MPPT Trackers	3
No.of Strings Per MPPT Tracker	2+2+2

 

I don't want to hijack this thread but I am also struggling with the whole Voc / Isc and ensuring the panels are wired up to optimise their performance. I have a 16kW Deye and 30 Jinko 560N panels. The specs for the Deye are as below with 3 MPPT’s and two strings per MPPT and the panel specs are Voc 50.47V, Isc 14.14A and Pmax 560W at STC.

I am in Cape Town and the panels are installed on two separate roofs which are both next to each other and face the same direction which is pretty much North and are at the same angle. They are installed as 5 X 4 = 20 and 5 X 2 =10 panels. So 20 panels on the one roof and 10 on the other.

I think the installer has put the panels up as 3 serialised strings of 10 panels to each MPPT. I have seen Voltages of 504V – 508V on the PV side when the load has decreased and it is midday and I really don’t want to cook this thing !

So my matchbox calculation, with very limited knowledge which is always a dangerous combination,  is at Zero degrees temperature Voc will increase to approximately 55.52V per panel (about a 10% uplift), meaning 555V per MPPT which can fry the MPPT’s.

The way I understand it is that to keep the MPPT as happy and efficient as possible you want to try and limit the voltage to a maximum of 425V as it’s range is 150 -425V ?

So what would be the best / most optimal way to connect the 30 panels to the Inverter ? 6 strings of 5 panels in each string ? That is only around 275 Volts though, is it better to run it higher ? Where does the Isc play a role in the calculations ?

Any input would be greatly appreciated !

Thanks, Grant.

PV String Input Data
Max. DC Input Power (W)			20800
Max. DC Input Voltage (V)	500
Start-up Voltage (V)	125
MPPT Range (V)	150~425
Rated DC Input Voltage (V)	370
PV Input Current (A)	26+26+26
Max. PV ISC (A)	44+44+44
No.of MPPT Trackers	3
No.of Strings Per MPPT Tracker	2+2+2

On the understanding that these are your panel specs:

I think you're right to be concerned; you are at risk of exceeding the Voltage limits and causing a failure with 10s on each MPPT. The alternative configuration you suggest of 5s2p on each MPPT should function okay. You'd be below the optimum operating Voltage, and on the odd occasion you might see a bit of current clipping to 26A, but you could at least sleep far easier.

An alternative option might be to run 8 in series on MPPT1 and MPPT2, and then for MPPT3 you could put a 7s2p  configuration, but that could get more complicated to set up with your panels being positioned as the currently are. Might be not critical anyway. For an installer to check/verify, if it makes sense.

 

On the understanding that these are your panel specs:

I think you're right to be concerned; you are at risk of exceeding the Voltage limits and causing a failure with 10s on each MPPT. The alternative configuration you suggest of 5s2p on each MPPT should function okay. You'd be below the optimum operating Voltage, and on the odd occasion you might see a bit of current clipping to 26A, but you could at least sleep far easier.

An alternative option might be to run 8 in series on MPPT1 and MPPT2, and then for MPPT3 you could put a 7s2p  configuration, but that could get more complicated to set up with your panels being positioned as the currently are. Might be not critical anyway. For an installer to check/verify, if it makes sense.

Thank you for the insight, panels are the JKM560N-72HL4-V but v similar specs to the ones above.

I will get another installer out to have a look as I am a bit worried about frying the MPPT's !

Appreciate your input Greenfields !

 

 

I don't want to hijack this thread but I am also struggling with the whole Voc / Isc and ensuring the panels are wired up to optimise their performance. I have a 16kW Deye and 30 Jinko 560N panels. The specs for the Deye are as below with 3 MPPT’s and two strings per MPPT and the panel specs are Voc 50.47V, Isc 14.14A and Pmax 560W at STC.

I am in Cape Town and the panels are installed on two separate roofs which are both next to each other and face the same direction which is pretty much North and are at the same angle. They are installed as 5 X 4 = 20 and 5 X 2 =10 panels. So 20 panels on the one roof and 10 on the other.

I think the installer has put the panels up as 3 serialised strings of 10 panels to each MPPT. I have seen Voltages of 504V – 508V on the PV side when the load has decreased and it is midday and I really don’t want to cook this thing !

So my matchbox calculation, with very limited knowledge which is always a dangerous combination,  is at Zero degrees temperature Voc will increase to approximately 55.52V per panel (about a 10% uplift), meaning 555V per MPPT which can fry the MPPT’s.

The way I understand it is that to keep the MPPT as happy and efficient as possible you want to try and limit the voltage to a maximum of 425V as it’s range is 150 -425V ?

So what would be the best / most optimal way to connect the 30 panels to the Inverter ? 6 strings of 5 panels in each string ? That is only around 275 Volts though, is it better to run it higher ? Where does the Isc play a role in the calculations ?

Any input would be greatly appreciated !

Thanks, Grant.

PV String Input Data
Max. DC Input Power (W)			20800
Max. DC Input Voltage (V)	500
Start-up Voltage (V)	125
MPPT Range (V)	150~425
Rated DC Input Voltage (V)	370
PV Input Current (A)	26+26+26
Max. PV ISC (A)	44+44+44
No.of MPPT Trackers	3
No.of Strings Per MPPT Tracker	2+2+2

From the values you have seen and the cold front in your area it is a major risk to allow over 500V to a MPPT. 

The specs you quote clearly shows 500V as a maximum voltage at anytime. This needs urgent attention.