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Verify the lowest ambient temperature of the installation location. The rated Voc on the solar module
nameplate is obtained at STC (Standard Testing Conditions = 77°F/25°C). As the ambient temperature
drops, the solar module Voc increases. Please ensure the maximum solar string voltage, corrected at
the lowest temperature, does not exceed the inverter’s maximum input voltage of 480VDC.
PV Input Data Description Parameter
DC Input Voltage Range
Range required for the unit to operate up
to max input
100–480 VDC
Load Output Minimum Voltage
Minimum voltage needed to output power
>140 VDC
MPP Operating Voltage Range Range where the MPPT can track 120–385 VDC
Nominal MPPT Voltage
The MPPT will operate most optimally at
320 VDC
Nominal MPPT Amperage
The MPPT will operate most optimally at
17A
Maximum MPPT Amperage
The MPPT can accept up to this amperage
(clipping will occur past this value)
25A
Maximum Utilized Solar Power
Wattage the unit can utilize from array
after considering all power loss factors
8kW
5.5.2 STRING SIZING
When solar modules are put in a series string, the voltage multiplies times the number of
modules and the amperage stays the same as each module.
For example: Using solar modules that have a 40VDC Voc (@77ºF) with a Max Power
amperage of 10 Amps (Imp) - 10 modules wired in a series string would have a Voc of 400 VDC
(@77ºF) and a string amperage of 10 Amps. When the temperature lowers, the voltage can
rise above the maximum allowed by the inverter and damage will result.
To determine how many modules per string; first verify the lowest possible ambient temperature of
the installation location. Next, find the rated Voc, Vmp, Isc and Imp of the solar module at 77ºF and the
temperature coecients for voltage and power. Then, calculate highest possible Voc for the entire
string when the ambient temperature falls to the lowest possible ambient temperature upon sunrise.
To make this calculation, use a string calculator or consult a solar designer or solar electrician.
Finally, calculate the maximum current of the string (Isc) so as not to exceed the inverter’s
MPPT circuit ratings of 25A (see note at end of section). Double check if the calculated Vmp
range is within the 120-385 VDC optimal MPPT circuit operating range. It is recommended to
consult a solar designer for assistance.
Each MPPT is rated for 4kW of solar input which leads to 8kW PV input in total.
Size the PV strings accordingly for maximum gain.
Damage WILL occur if the string voltage exceeds the inverter’s maximum
REMINDER
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