Grounding, Bonding, and Overcurrent Protection
What this domain tests
Grounding and bonding questions are the most concept-heavy on the exam. You must distinguish system grounding (connecting the source neutral to earth) from equipment grounding (providing a fault path) and from bonding (connecting metal parts together). Overcurrent protection questions test coordination, device selection, and the rules for taps and motor circuits.
Concepts to master
- Grounded vs. grounding vs. bonding: the grounded conductor is the neutral; the grounding electrode conductor connects to earth; the equipment grounding conductor provides the fault-return path; bonding jumpers connect metal parts.
- Grounding electrode system: rods, plates, pipes, concrete-encased electrodes, and the requirement to use all available electrodes and bond them together.
- Main bonding jumper: the single connection between the grounded conductor and the equipment grounding system, made only at the service (or separately derived system).
- Equipment grounding conductor sizing: by table, based on the rating of the overcurrent device ahead of the equipment.
- Overcurrent device types: branch-circuit breakers, fuses, and the rules for series ratings and tap conductors.
- Motor circuits: overload protection is separate from branch-circuit short-circuit and ground-fault protection.
Traps in questions
A frequent trap is a downstream panel with a neutral-to-ground bond - that creates parallel return paths and is a violation. Another is sizing the equipment grounding conductor from the conductor size rather than the overcurrent device rating. Questions also test whether a grounding electrode conductor must be continuous and whether taps are permitted.
Rule of thumb
Size the equipment grounding conductor from the rating of the overcurrent device protecting the circuit, not from the phase conductor ampacity. Bond the neutral to ground at exactly one point: the service disconnect or the separately derived system.
Worked example
A 400 A feeder protected by a 400 A breaker requires an equipment grounding conductor sized per the table for 400 A, which is typically 3 AWG copper. If the feeder were upsized for voltage drop, the EGC may need proportional upsizing - a common review finding.