Which statement is true about Class 3 power sources?

Which statement is true about Class 3 power sources?

• A. A Class 3 circuit must use a listed class 3 limited or nonlimited power source.
• B. Class 3 circuits may use any power source.
• C. Class 3 sources are always larger than Class 2 sources.
• D. Class 3 sources are not subject to NEC rules.

Answer: (A)

Class 3 circuits are energy-limited by design, so they must be fed from a power source that is specifically listed for Class 3 use. A listed Class 3 power source — whether it’s labeled limited or nonlimited — has been tested and labeled to meet safety requirements for Class 3 operation. This listing ensures the output is controlled and that the circuit, protection, and wiring practices are appropriate and compliant with the NEC. Using a non-listed or non-Class 3 source would bypass that safety assurance and violate code requirements. The idea that any power source can be used is not correct, and the size of the source or the absence of NEC rules isn’t the deciding factor—the need for a listed Class 3 source is.

Class 3 circuits are energy-limited by design, so they must be fed from a power source that is specifically listed for Class 3 use. A listed Class 3 power source — whether it’s labeled limited or nonlimited — has been tested and labeled to meet safety requirements for Class 3 operation. This listing ensures the output is controlled and that the circuit, protection, and wiring practices are appropriate and compliant with the NEC. Using a non-listed or non-Class 3 source would bypass that safety assurance and violate code requirements. The idea that any power source can be used is not correct, and the size of the source or the absence of NEC rules isn’t the deciding factor—the need for a listed Class 3 source is.