EGC means equipment grounding conductor.
It is the conductor that connects electrical equipment, raceways, and metal enclosures back to the grounding path of the electrical system.
The EGC is not there to carry normal load current.
Its purpose is to provide a path for fault current so the circuit breaker or fuse can operate when a ground fault happens.
What Does an EGC Do?
An equipment grounding conductor helps protect people and equipment when there is a fault.
For example, if an energized conductor contacts a metal motor enclosure, the EGC provides a low-impedance path back to the source.
That fault current can help the OCPD open and clear the fault.
An EGC can be:
- A copper grounding conductor
- An aluminum grounding conductor where permitted
- A metal raceway that qualifies as an equipment grounding path
What Determines EGC Size?
The minimum EGC size is generally based on the rating of the circuit’s OCPD.
The OCPD may be:
- A circuit breaker
- A fuse
This means you first identify the OCPD protecting the circuit, then use the applicable grounding-conductor requirements to determine the minimum EGC size.
The EGC size is not always based only on the phase conductors.
Quick Motor Circuit Example
Say a motor-circuit calculation gives you an OCPD result.
Once the OCPD is known, use that protective-device rating to determine the EGC size required for the circuit.
For a motor circuit, the process looks like this:
- Enter the motor phase
- Enter the motor horsepower
- Enter the motor voltage
- Review the FLC result
- Review the OCPD result
- Use the OCPD result to determine the EGC size
That is why the EGC result is connected to the overcurrent protective device used for the circuit.
How Sparky Toolbox Helps
The Sparky Toolbox Motor Calculator keeps the basic motor-circuit result in one place.
Enter:
- Phase
- Horsepower
- Voltage
The calculator shows:
- FLC
- OCPD
- Wire size
- EGC size
That gives you a faster starting point when planning a motor circuit and building a material list.
Important Reminder
EGC requirements can change based on conductor upsizing, raceway type, equipment ratings, fault-current conditions, local amendments, and other project details.
Always verify the applicable Code requirements, equipment information, approved plans, and local inspection requirements before installation.