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Guidelines for Matching PV Array Size to Xantrex Grid Tie Solar Inverter Input
• Consider the expected V
oc
of the string under all possible conditions. The
panel manufacturer provides a V
oc
rating per panel, but it is usually rated at
25
°C (77 °F). Ensure that the V
oc
rating at the coldest ambient temperature
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 article 690 of the NEC. You need to determine the
coldest temperatures expected on the site, and size the array strings
accordingly. To prevent inverter damage, the array’s maximum DC voltage in
the coldest expected temperature, with both manufacturer coefficient and
NEC derating, must not exceed 600 Vdc.
• Panel voltage decreases in high temperatures. This will affect the panels’ V
MPP
and V
oc
. Again, the manufacturer’s coefficient must be used with the highest
expected temperature to determine the minimum V
MPP
and V
oc
.
Note:
The GT PV array sizing tool is available at www.xantrex.com.