1 string or 2 make any difference?

[aaapilot]

Configuring 14 panels (260 watt) to a Hawks Bay.  Any reason to do a single string of 14, higher voltage aprox 600v, versus 2 strings of 7 each, aprox 300v?  Attached are the sizing tool printouts for each configuration.  Yes, the 14 string exceeds the max VOC by 5 volts, so I could do 13 or they may not all test out to max output, but in theory, would 300 volts versus 600 volts have any positive/negative effects?  The array is aprox 120' from the Hawks Bay location.

[Vic]

Configuring 14 panels (260 watt) to a Hawks Bay.  Any reason to do a single string of 14, higher voltage aprox 600v, versus 2 strings of 7 each, aprox 300v?  Attached are the sizing tool printouts for each configuration.  Yes, the 14 string exceeds the max VOC by 5 volts, so I could do 13 or they may not all test out to max output, but in theory, would 300 volts versus 600 volts have any positive/negative effects?  The array is aprox 120' from the Hawks Bay location.

Hi aapilot2,

IMO,  you have NO CHOICE.  14 of your PVs in a single string is too great of a risk, to the HB.

Two identical strings in parallel,  seems to be the only way to go.

If the Voc rating of the HB is ever exceeded, it runs the great risk of permnent damage to the HB, IMO.

To me, max Voc ratings of CCs are hard, fast limits.  FWIW, Vic

[Vic]

aapilot2,

You are correct, you could use 13 PVs,  and the Voc should be OK.

I forget what is the maximum MPPT voltage for the HB,  was a bit concerned that the 13 PV string Vmp might be a bit too close to that MPPT upper limit when the PVs are cold.  Will check that.
EDIT:  > MPPT Range: 185 to 585 volts dc operating range <

Most MPPT Charge Controllers (CCs) operate a bit less efficiently when the input voltage is near the high limit.  I am unsure if that is a large factor with the HB.

It is great that MidNite has HB and Barcelona Beta String Sizing, now.  This String Sizer is still the best that I have ever used.

FWIW,   Vic

[aaapilot]

Thanks for input, Vic!  I can easily do a combiner for 2 strings, just trying to maximize efficiency with these high voltage CC's.  I may have to try both ways once the system is up and running to see for myself. As you said, I would not risk going over the max VOC, which makes the string planner worth its weight in gold!  Think I read in the Hawks Bay manual (?) that it has a circuit that throws the PV circuit breaker if voltage exceeds 600v, a built-in protection I assume

[Vic]

Thanks for input, Vic!  I can easily do a combiner for 2 strings, just trying to maximize efficiency with these high voltage CC's.  I may have to try both ways once the system is up and running to see for myself. As you said, I would not risk going over the max VOC, which makes the string planner worth its weight in gold!  Think I read in the Hawks Bay manual (?) that it has a circuit that throws the PV circuit breaker if voltage exceeds 600v, a built-in protection I assume

In an early Manuals for the Hawke's Bay or the Barcelona CCs,  I did not specifically see that the PV breaker/s would be tripped, if the PV input voltage exceeded some certain value.  BUT,  it sure seems like it should, and be another great idea!

Your comparisons between different PV string configurataions will be interesting.

Good Luck with your project.   Vic