Enter the rating of the fuse or circuit breaker protecting the circuit.
Copper (Cu)
Aluminum / Copper-Clad Aluminum (Al)
Required Ground Wire Size:
Understanding Ground Wire Sizing (NEC 250.122)
Correctly sizing the equipment grounding conductor (EGC) is critical for electrical safety. In the event of a ground fault, the ground wire provides a low-impedance path back to the source, ensuring that the circuit breaker trips quickly.
How Sizing is Determined
Unlike service grounding, which is based on the size of the service entrance conductors, Equipment Grounding Conductors (conductors run with the branch circuit or feeder) are sized based on the rating of the overcurrent protective device (circuit breaker or fuse) protecting that circuit.
Key Rules for EGC Sizing:
Material Type: Aluminum ground wires typically need to be larger than copper wires for the same ampacity due to lower conductivity.
Multiple Conductors: If you have multiple circuits in the same raceway, the ground wire is sized based on the largest overcurrent device in that conduit.
Voltage Drop: If the phase conductors are increased in size to account for voltage drop, the ground wire must be increased proportionately.