Article 100 Definitions. Class 1 Circuits.

Vehicle loop detectors are typically connected to the load side of a Class 1 power source and are an example of a Class 1 signaling circuit.
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Vehicle loop detectors are typically connected to the load side of a Class 1 power source and are an example of a Class 1 signaling circuit.

Code Change Summary: The definition of a Class 1 Circuit has been revised.

The requirements for Class 1 circuits have been removed from Article 725 and relocated to new Article 724.

A Class 1 circuit is the portion of the wiring system between the load side of the Class 1 power source and the connected equipment.

According to new Section 724.40, Class 1 circuits are limited to 30 volts and 1000 volt-amperes. Previous editions of the NEC® described Non-power limited Class 1 remote-control and signaling circuits in Article 725. Technically, these circuits are actually “branch circuits”. Since the requirements for branch circuits are covered in NEC® Chapters 1-4, they are not covered in new Article 724.

This change warranted the need to revise the definition of a Class 1 Circuit during the 2023 code cycle.

The previous definition described wiring between the load side of an overcurrent device or power-limited supply and the connected equipment. The new definition eliminates “overcurrent device” from the description since the wiring from the load side of an overcurrent device to the outlet where equipment is connected is technically a “branch circuit” which is also defined in Article 100.

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:

Class 1 Circuit. The portion of the wiring system between the load side of the overcurrent device or power-limited supply and the connected equipment.

2023 Code Language:

Class 1 Circuit. The portion of the wiring system between the load side of the Class 1 power source and the connected equipment.

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Article 100 Definitions. Class 1 Circuits.

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

Based on the 2023 NEC, which of the following is true?

A: A Class 1 Circuit is the portion of the wiring on the line side of a circuit breaker.
B: A Class 1 Circuit is the portion of the wiring system between the load side of the Class 1 power source and the connected equipment.
C: Class 1 Circuits are the same as Class 3 Circuits.
D: Class 1 Circuits are the same as Class 2 Circuits.
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