What size equipment grounding conductor is used with the following sizes of nonmetallic-sheathed cable?
a. 14 AWG
b. 12 AWG
c. 10 AWG
d. & AWG
The correct answer and explanation is :
The size of the equipment grounding conductor (EGC) used with nonmetallic-sheathed (NM) cables is determined by the gauge of the circuit conductors and is typically specified in the National Electrical Code (NEC), specifically in NEC Table 250.122. The EGC provides a safe path to ground for fault current in the event of a short circuit or ground fault, ensuring that the electrical system is properly protected.
Here is the required equipment grounding conductor size for each of the given conductor sizes:
a. 14 AWG
For a 14 AWG conductor, the required EGC size is 14 AWG. According to NEC Table 250.122, for circuit conductors up to 20 amps (such as the 14 AWG wire), the grounding conductor is typically sized the same as the circuit conductor.
b. 12 AWG
For a 12 AWG conductor, the required EGC size is 12 AWG. This is again in line with the NEC Table 250.122, which specifies that for 20-amp circuits using 12 AWG, the grounding conductor should be the same size as the conductor (12 AWG).
c. 10 AWG
For a 10 AWG conductor, the required EGC size is 10 AWG. According to NEC Table 250.122, for 30-amp circuits using 10 AWG wire, the grounding conductor is the same size as the circuit conductor.
d. 8 AWG
For an 8 AWG conductor, the required EGC size is 8 AWG. For 40-amp circuits with 8 AWG wire, the EGC should be sized per NEC guidelines to match the circuit conductor size.
Explanation:
The purpose of the equipment grounding conductor is to provide a safe and reliable path for fault currents to return to the earth. The NEC provides these requirements to ensure proper protection for people and equipment by allowing the grounding conductor to carry fault current without excessive voltage or overheating. By ensuring the size of the grounding conductor is equal to or greater than the specified value in NEC Table 250.122, the electrical system is protected from potential faults and hazards that may arise due to damaged or malfunctioning wiring.
If the grounding conductor is too small for the size of the circuit conductor, it may not carry enough current to trip the breaker in the event of a fault, leading to possible hazards. Therefore, always refer to the NEC to determine the appropriate grounding conductor size for the specific wire gauge used in any electrical installation.