Xantrex GT2.5-NA Owner's Manual page 33

Guidelines for Matching PV Array Size to Xantrex Grid Tie Solar Inverter Input
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For determining the number of panels required in the PV string (panels connected
in series), you must ensure that the following requirements are met:
1. To avoid damage to the inverter, ensure that the PV array output will never
exceed 600 Vdc under any conditions.
2. Do not exceed the maximum array short circuit-current rating marked on the
inverter.
3. To achieve maximum energy harvest from your array, ensure that the V
(voltage at maximum power) does not drop below 195 Vdc or increase above
550 Vdc under most conditions.
Guidelines to help you meet these requirements:
• Consider the expected V
panel manufacturer provides a V
25 C (77 F). Ensure that the V
° °
does not exceed 600 Vdc. Panel voltage increases in cold temperatures—the
panel manufacturer should be able to provide a coefficient of voltage increase
per degree.
• The NEC also has required temperature/voltage deratings that must be used;
these can be found in Table 690.7 of the 2002 NEC handbook. You need to
determine the coldest temperatures expected on the site, and size the array
strings accordingly. The array's maximum DC voltage in coldest expected
temperature, with both manufacturer coefficient and NEC derating, must not
exceed 600 Vdc to prevent inverter damage.
• Panel voltage decreases in high temperatures. This will affect the panels'
V . Again, the manufacturer's coefficient must be used with the highest
MP
expected temperature to determine the minimum V
Once you know the specifications of your panels, all these factors will help
determine the maximum and minimum number of panels that can be used.
Note:
The GT PV array sizing tool is available at www.xantrex.com.
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of the string under all possible conditions. The
OC
rating per panel, but it is usually rated at
OC
rating at the coldest ambient temperature
OC
Planning the Installation
MP
.
MP
2–7