The Equipment Grounding Conductor (EGC) is an essential component of electrical safety. It provides a path for fault currents to flow from the metallic frames of electrical equipment to the ground, ensuring the rapid operation of circuit protection devices (like circuit breakers or fuses) in case of a fault. Here are some key aspects of the EGC:
- Purpose: The primary function of the EGC is to connect non-current-carrying metallic parts of electrical equipment (such as the metal casing of an appliance) to the system’s grounded (neutral) conductor or to the grounding electrode, or both. This ensures that if a live wire touches the metal parts of an equipment due to a fault, the resulting surge in current will trip the circuit breaker or blow the fuse, thereby de-energizing the equipment and preventing electric shock.
- Identification: In the United States, as per the National Electrical Code (NEC), the EGC is typically either a green wire or a bare wire without insulation.
- Path: The EGC provides a low-resistance path for fault current to flow back to the source, allowing protective devices to operate quickly and minimize potential electric shock hazards.
- Bonding: Alongside the EGC, all metallic components in an electrical system need to be electrically interconnected (bonded) to ensure they have the same electrical potential. This bonding process ensures that there are no potential differences between different parts, which could result in electrical shock.
- Isolation from Neutral in Equipment: In a correctly wired system, neutral conductors and EGCs are separated at the point of use, like in outlets or appliances. They are only bonded together at one point, typically at the main service entrance or the main panel. This prevents parallel paths for normal circuit current to flow on the grounding system, which could be dangerous.
- Grounding Electrode System: The EGC will be connected to a grounding electrode system, such as ground rods, metal water pipes, or other types of electrodes. This connection ensures that fault currents have a path into the earth, further enhancing safety.
- Sizing: The size (gauge) of the EGC is determined based on the size of the circuit’s overcurrent protection device and the size of the circuit conductors. The NEC provides tables and requirements for determining the appropriate size of the EGC for a given circuit.
The Equipment Grounding Conductor plays a pivotal role in electrical safety. By ensuring rapid disconnection of faulted equipment and minimizing potential voltage on equipment casings, the EGC protects both people and equipment from electrical hazards.