Installation

Guidelines for Matching PV Array Size to Xantrex Grid Tie Solar Inverter Input

•Consider the expected Voc of the string under all possible conditions. The panel manufacturer provides a Voc rating per panel, but it is usually rated at 25 °C (77 °F). Ensure that the Voc 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’ VMPP and Voc. Again, the manufacturer’s coefficient must be used with the highest expected temperature to determine the minimum VMPP and Voc.

Note: The GT PV array sizing tool is available at www.xantrex.com.

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