Calculation of PV System Voltage

April 25, 2014
Understanding the system voltage requirements for PV systems as outlined in the 2011 NEC.

The _____ of a DC photovoltaic source circuit or output circuit must be calculated as the sum of the rated open-circuit voltage of the series-connected photovoltaic modules multiplied by the correction factor provided in Table 690.7.

a) minimum allowable ampacity of conductors
b) maximum allowable ampacity of conductors
c) minimum photovoltaic system voltage
d) maximum photovoltaic system voltage

See answer and applicable Code reference

The correct answer is: d) maximum photovoltaic system voltage

The rules for installation of solar photovoltaic (PV) systems are presented in Art. 690 of the 2011 NEC. Circuit requirements for PV systems can be found in Part II of this Article. As noted in a portion of Sec. 690.7(A), "In a DC photovoltaic source circuit or output circuit, the maximum photovoltaic system voltage for that circuit shall be calculated as the sum of the rated open-circuit voltage of the series-connected photovoltaic modules corrected for the lowest expected ambient temperature. For crystalline and multicrystalline silicon modules, the rated open-circuit voltage shall be multiplied by the correction factor provided in Table 690.7."

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