Code Change Summary: A new definition of a “PV String Circuit” was added to Article 100 and several previous PV related definitions were deleted.

In the 2023 NEC^®, a new definition of a PV String Circuit was added to Article 100. A PV string circuit includes PV source circuit conductors of one or more series-connected PV modules.

For years, common industry terminology for a group of PV modules wired in series has been “string”, “series string”, or “string circuit”. The NEC^® has never had a definition of a PV String Circuit until now.

Additionally, several previous PV definitions have been deleted and/or consolidated and are now considered a “PV DC Circuit (PV System DC Circuit)” which applies to “any dc conductor in PV source circuits, PV string circuits, and PV dc-to-dc converter circuits”.

The deleted PV related terminology is no longer used in Article 690 and therefore the definitions are no longer needed. The following changes occurred as well as the relocation of the definitions from 690.2 to Article 100:

• DC-to-DC Converter Output Circuit – Deleted but now covered under the definition of a DC-to-DC Converter Circuit in Article 100, and also considered a PV DC Circuit.
• DC-to-DC Converter Source Circuit - Deleted but now covered under the definition of a DC-to-DC Converter Circuit in Article 100, and also considered a PV DC Circuit.
• PV Output Circuit – Deleted but now covered under the definition of a PV Source Circuit in Article 100, and also considered a PV DC Circuit.

In past editions of the NEC^® a PV Output Circuit was created when two or more series strings were connected in parallel. Now, this circuit will simply be incorporated into the revised definition of a PV Source Circuit to reduce confusing terminology.

The move to update the PV terminology was based largely in part from a public input from the PV Industry Forum (PVIF) who suggested that the current definitions and usage of the terminology throughout Article 690 has caused confusion among inspectors, installers, and system designers for years.

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 2023 NEC^® edition of NFPA 70.

2020 Code Language:

690.2 Definitions.

DC-to-DC Converter Output Circuit. The dc circuit conductors connected to the output of a dc combiner for dc-to-dc converter source circuits.

DC-to-DC Converter Source Circuit. Circuits between dc-to-dc converters and from dc-to-dc converters to the common connection point(s) of the dc system.

PV Output Circuit. The dc circuit conductors from two or more connected PV source circuits to their point of termination.

PV Source Circuit. The dc circuit conductors between modules and from modules to dc combiners, electronic power converters, or a dc PV system disconnecting means.

2023 Code Language:

Article 100 Definitions.

PV DC Circuit (PV System DC Circuit). Any dc conductor in PV source circuits, PV string circuits, and PV dc-to-dc converter circuits. (690)

• N PV DC Circuit (PV System DC Circuit). Any dc conductor in PV source circuits, PV string circuits, and PV dc-to-dc converter circuits. (690)
• N PV DC Circuit, Source. (PV Source Circuit). The PV dc circuit conductors between modules in a PV string circuit, and from PV string circuits or dc combiners, to dc combiners, electronic power converters, or a dc PV system disconnecting means. (690)
• N PV DC Circuit, String. (PV String Circuit). The PV source circuit conductors of one or more series-connected PV modules. (690)