National Electrical Code (NEC) Definitions on Grounding and Bonding

Importance of Terminology

• Terminology is critical for effective communication around grounding and bonding.
• Definitions ensure a common language and understanding.

Key Definitions from Article 100

Ground

• Defined as the earth.
• Connecting to the ground means connecting to the earth.

Grounding Electrode

• Conducting object used to make a direct electrical connection to the earth.
• Examples: ground rod, grounding grid, structural steel, water pipe.
• Multiple electrodes can form a Grounding Electrode System.

Grounding Electrode Conductor

• Connects the system neutral or grounded phase conductor/equipment to the grounding electrode system.

Grounded vs. Ungrounded

• Grounded: Connected to the earth or to a conductive body extending that connection.
• Ungrounded: Not connected to the ground or conductive body.

Grounded Conductor

• System/circuit conductor intentionally connected to earth (often referred to as neutral).

Ungrounded Conductor

• Circuit conductor not intentionally connected to earth (usually phase conductors).

Grounding Conductor

• Connects equipment or grounded circuit of a wiring system to a grounding electrode/system.

Bonding

Definition

• Bonded: Connected to establish electrical continuity and conductivity.

Bonding Conductors (Jumpers)

• Ensure required electrical conductivity between metal parts.

Main Bonding Jumper

• Connection between grounded circuit conductor and equipment grounding conductor.

Supply Side Bonding Jumper

• Installed on the supply side or within service equipment, ensuring conductivity between metal parts.

Transformers and Separately Derived Systems

Separately Derived System

• Electrical source with no direct connections to circuit conductors of other sources except through grounding and bonding.
• E.g., Delta Y grounded transformer, generator ground rod bonding.

Importance of Bonding in Generators

• Influences the type of transfer switch: four-pole needed if neutral is bonded (creates separately derived system).
• Incorrect bonding can lead to circulating currents and faulty GFCI operation.

Non-Separately Derived System

• Examples: downstream panel boards, generators without established neutral ground bond.

System Bonding Jumper

• Connects grounded circuit to supply side bonding jumper.

Equipment Bonding Jumpers

• Connections between equipment grounding conductors.

Equipment Grounding Conductor

• Conductive path connecting metal parts of equipment to system neutral/grounded phase conductor.
• Should carry fault current effectively.

System Grounding

Solidly Grounded vs. Impedance Grounded Systems

• Solidly Grounded: Direct connection to earth with no impedance.
• Impedance Grounded: Connection to earth through impedance.

Objectionable Currents

• Current on effective ground fault path during non-fault condition.
• Example: Motion sensor switches potentially causing current on grounding conductor.
• NEC prohibits objectionable currents and requires proper neutral conductor use.

Conclusion

• Correct use of terms is crucial for effective communication and electrical safety.
• Understanding NEC definitions helps ensure compliant and safe electrical installations.