Hi. This is my first post, so I apologize in advance for any faux pas. I have sized an off-grid PV system for a cabin in the high desert of west TX. Lots of sun, hot summer days some cold winter days, and notable winds. I used PVWATTS and several online calculators to estimate my daily and seasonal loads and system requirements. Based on that I purchased an EG4 6000XP inverter and two, EG4 280Ah batteries. I am now selecting the size and number of solar panels/modules.
I am looking at the Aptos 440W monofacial panels (DNA-120-MF10-440W), with the following specs:
Isc: 3.73 A
Imp: 12.26 A
Voc: 41.02 V
Vmp: 35.87 V
Temp Coeff (Pmmp): -0.35 %/°C
Temp Coeff (Voc): -0.27 %/°C
I calculated each panel's voltages at low and high expected temps (14 °F & 105 °F) and assumed a cell temperature increase of 45 °F for flush-mounted modules on a sheet metal roof (painted light green).
Voc max: 44.7 V
Voc min: 30.1 V
The EG4 6000XP's specs pertaining to PV input are:
Number of MPPTs: 2
Inputs per MPPT: 1
Max Usable Input Current: 17/17 A
Max Short Circuit Input Current: 25/25 A
DC Input Voltage Range: 100-480 VDC
Unit Startup Voltage: 100 VDC± 10VDC (though I read a min of 160VDC is better)
MPPT Operating Voltage Range: 120-385 VDC
Nominal MPPT Voltage: 320 VDC
Max Utilized Solar Power: 8000 W (4000 W per MPPT)
Recommended Max Solar Input: 10,000 W (5000 W per MPPT)
I am planning to start with 1 string of 6 Aptos panels in series, plugged into 1 MPPT input. That appears to stay well within the inverter specs for 1 MPPT (181-268 VDC and 2214-3286W solar power).
If I install 8 panels now, the input voltage range changes to 241-357VDC, but the solar power input changes to 2952-4382W. The high wattage here exceeds the inverter's usable input, so I assume the excess gets clipped. But it seems that should only occur at the array's peak output.
So, is 8 panels to much to start with? might it harm the inverter? I can get back the clipped watts and use the other the MPPT input if/when I add more panels.
Thanks.
I am looking at the Aptos 440W monofacial panels (DNA-120-MF10-440W), with the following specs:
Isc: 3.73 A
Imp: 12.26 A
Voc: 41.02 V
Vmp: 35.87 V
Temp Coeff (Pmmp): -0.35 %/°C
Temp Coeff (Voc): -0.27 %/°C
I calculated each panel's voltages at low and high expected temps (14 °F & 105 °F) and assumed a cell temperature increase of 45 °F for flush-mounted modules on a sheet metal roof (painted light green).
Voc max: 44.7 V
Voc min: 30.1 V
The EG4 6000XP's specs pertaining to PV input are:
Number of MPPTs: 2
Inputs per MPPT: 1
Max Usable Input Current: 17/17 A
Max Short Circuit Input Current: 25/25 A
DC Input Voltage Range: 100-480 VDC
Unit Startup Voltage: 100 VDC± 10VDC (though I read a min of 160VDC is better)
MPPT Operating Voltage Range: 120-385 VDC
Nominal MPPT Voltage: 320 VDC
Max Utilized Solar Power: 8000 W (4000 W per MPPT)
Recommended Max Solar Input: 10,000 W (5000 W per MPPT)
I am planning to start with 1 string of 6 Aptos panels in series, plugged into 1 MPPT input. That appears to stay well within the inverter specs for 1 MPPT (181-268 VDC and 2214-3286W solar power).
If I install 8 panels now, the input voltage range changes to 241-357VDC, but the solar power input changes to 2952-4382W. The high wattage here exceeds the inverter's usable input, so I assume the excess gets clipped. But it seems that should only occur at the array's peak output.
So, is 8 panels to much to start with? might it harm the inverter? I can get back the clipped watts and use the other the MPPT input if/when I add more panels.
Thanks.
