Grounding and bonding work together to protect people from shock and to ensure overcurrent devices operate during faults. They are distinct concepts — understanding the difference is essential for both the exam and the field.

Grounding vs. Bonding (NEC 250.2)

• Grounding — connecting to earth to establish a reference voltage; dissipates lightning and overvoltage surges
• Bonding — connecting conductive parts together to maintain equal potential; provides the low-impedance fault path that trips the overcurrent device
• A ground rod alone cannot clear a fault — the bonding/EGC path does that

Equipment Grounding Conductor (EGC)

• Identified by green insulation, green-with-yellow-stripe, or bare copper (NEC 250.119)
• Carries fault current back to the source so the breaker or fuse operates
• Does NOT carry current under normal conditions
• Must be continuous, low-impedance, and sized per NEC Table 250.122

Grounded Conductor (Neutral)

• Identified by white or gray insulation — current-carrying under normal single-phase conditions
• Connected to earth at the service entrance per NEC 250.24
• Must NOT be re-bonded to ground at downstream panels (subpanels) — this creates dangerous parallel current paths through metal conduit and equipment enclosures

Service Grounding (NEC 250.24)

• Service-entrance equipment must be grounded
• Grounding Electrode Conductor (GEC) connects the service neutral to the grounding electrode system
• Grounding electrode system includes: ground rod, metal water pipe, concrete-encased electrode (Ufer), ground ring
• The service panel is the only place neutral and ground are bonded in a separately derived system

GFCI vs. EGC

• GFCI monitors imbalance between hot and neutral — trips at 4–6 mA leakage
• EGC provides the fault path that causes the overcurrent device to open
• A GFCI does NOT require an EGC to function — it compares hot/neutral balance
• Both protect against shock: GFCI reacts faster to small leakage; EGC clears bolted faults

Key References

• NEC 2023 Article 250 — Grounding and Bonding
• NEC 250.4 — General requirements for grounding and bonding
• NEC 250.24 — Grounding service-supplied AC systems
• NEC 250.119 — Identification of EGC by color
• NEC Table 250.122 — Minimum size EGC for grounding raceways and equipment