690.7 Maximum Voltage
PV system dc circuits on or in buildings shall be permitted to have a maximum voltage no greater than 1000 volts. PV system dc circuits on or in one- and two-family dwellings shall be permitted to have a maximum voltage no greater than 600 volts. Where not located on or in buildings, listed dc PV equipment, rated at a maximum voltage no greater than 1500 volts, shall not be required to comply with Parts II and III of Article 490.
- The sum of the PV module-rated open-circuit voltage of the series-connected modules corrected for the lowest expected ambient temperature using the open-circuit voltage temperature coefficients in accordance with the instructions included in the listing or labeling of the module
- For crystalline and multicrystalline silicon modules, the sum of the PV module-rated open-circuit voltage of the series-connected modules corrected for the lowest expected ambient temperature using the correction factors provided in Table 690.7(A)
- For PV systems with an inverter generating capacity of 100 kW or greater, a documented and stamped PV system design, using an industry standard method maximum voltage calculation provided by a licensed professional electrical engineer
Informational Note No. 1: One source for lowest-expected, ambient temperature design data for various locations is the chapter titled "Extreme Annual Mean Minimum Design Dry Bulb Temperature" found in the ASHRAE Handbook — Fundamentals, 2017. These temperature data can be used to calculate maximum voltage.
Informational Note No. 2: One industry standard method for calculating maximum voltage of a PV system is published by Sandia National Laboratories, reference SAND 2004-3535, Photovoltaic Array Performance Model.
|Correction Factors for Ambient Temperatures Below 25°C (77°F). (Multiply the rated open-circuit voltage by the appropriate correction factor shown below.)|
|Ambient Temperature (°C)||Factor||Ambient Temperature (°F)|
|24 to 20||1.02||76 to 68|
|19 to 15||1.04||67 to 59|
|14 to 10||1.06||58 to 50|
|9 to 5||1.08||49 to 41|
|4 to 0||1.10||40 to 32|
|—1 to —5||1.12||31 to 23|
|—6 to—10||1.14||22 to 14|
|—11 to —15||1.16||13 to 5|
|—16 to—20||1.18||4 to —4|
|—21 to —25||1.20||—5 to—13|
|—26 to —30||1.21||—14 to—22|
|—31 to —35||1.23||—23 to —31|
|—36 to —40||1.25||—32 to —40|