Journeyman Electrician Exam (NEC)Control Devices and MotorsMedium
A motor control circuit uses a 120V AC supply. The control circuit conductors are installed in a raceway and are protected by a 15A overcurrent protective device. According to NEC 430.72(A), what is the minimum gauge (AWG) permitted for these control circuit conductors if they do not extend beyond the control enclosure?
- A14 AWG
- B16 AWG
- C12 AWG
- D18 AWG
Show answer & explanationAnswer & explanation
Correct answer: B. 16 AWG
NEC 430.72(A) Table 430.72(A) specifies minimum conductor sizes for motor control circuits. For a 120V circuit protected by a 15A overcurrent device, if the conductors do not extend beyond the control enclosure, the minimum conductor size permitted is 16 AWG.
Why the other options are wrong
- A. 14 AWG is permitted and larger than required, but 16 AWG is the minimum.
- C. 12 AWG is permitted and larger than required, but 16 AWG is the minimum.
- D. 18 AWG is generally permitted for smaller OCPD ratings or specific conditions, but not for 15A with this scope.
Motor Control Circuit Conductor Sizing (NEC 430.72(A))
NEC Table 430.72(A) specifies minimum conductor sizes for motor control circuits based on the OCPD rating and circuit voltage. For 120V circuits with 15A protection, 16 AWG is typically the minimum when conductors do not extend beyond the control enclosure.
- Minimum conductor size depends on OCPD rating and voltage.
- Table 430.72(A) provides specific requirements.
- Smaller gauges (e.g., 18 AWG, 16 AWG) are allowed for control circuits.
- Scope of conductor routing (within/beyond enclosure) impacts sizing.
Memory trick: Fifteen amps, inside the box, sixteen gauge unlocks.