690.7 Maximum Voltage.

The maximum voltage of PV system dc circuits shall be the highest voltage between any two conductors of a circuit or any conductor and ground.
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The maximum voltage of PV system dc circuits shall be the highest voltage between any two conductors of a circuit or any conductor and ground.

Code Change Summary: Revised code language intends to simplify the rules on maximum PV system DC circuit voltage.

Determining the maximum PV system DC circuit voltage is critical to select the right conductors and equipment, and to ensure that the DC voltage falls within the allowable limits permitted for PV systems on or in a building, on or in a one- or two-family dwelling, or ground mounted.

In the 2020 NEC, a change was made to make it clear that there is a direct relation between the maximum voltage of PV system DC circuits and equipment working space.

“Working space” is a specific measurement in relation to the electrical equipment for the worker performing service or maintenance. Working space dimensions for installations operating at 1000 volts or less are covered in Part II of Article 110 whereas working space for installations operating over 1000 volts is covered in Part III of Article 110.

In a PV system with a maximum DC circuit voltage of 947 volts, NEC Table 110.26(A)(1) would require a specific working space dimension in front of PV electrical equipment that is likely to be examined or serviced while energized. This dimension would be determined from using condition 1, 2, or 3 under the table.

Below is a preview of the NEC. See the actual NEC text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC edition of NFPA 70.

2017 Code Language:

690.7 Maximum Voltage. The maximum voltage of PV system dc circuits shall be the highest voltage between any two circuit conductors or any conductor and ground. PV system dc circuits on or in one- and two-family dwellings shall be permitted to have a maximum voltage of 600 volts or less.

PV system dc circuits on or in other types of buildings shall be permitted to have a maximum voltage of 1000 volts or less. Where not located on or in buildings, listed dc PV equipment, rated at a maximum voltage of 1500 volts or less, shall not be required to comply with Parts II and III of Article 490.

2020 Code Language:

690.7 Maximum Voltage. The maximum voltage of PV system dc circuits shall be the highest voltage between any two conductors of a circuit or any conductor and ground. The maximum voltage shall be used to determine the voltage and voltage to ground of circuits in the application of this Code. Maximum voltage shall be used for conductors, cables, equipment, working space, and other applications where voltage limits and ratings are used.

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.

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690.7 Maximum Voltage.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Based on the 2020 NEC, which of the following is true for a PV system on a commercial building?

A: The maximum PV system DC circuit voltage is 600 volts.
B: PV system DC circuits on or in buildings shall be permitted to have a maximum voltage no greater than 1000 volts.
C: PV system DC circuits on the building shall be no more than 2000 volts.
D: PV system AC circuits in the building shall be no more than 600 volts.
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