Module 3 · 40 minutes
Grounding, bonding, and fault clearing
Learn the conductors and connections that create an effective ground-fault current path.
Learning objectives
By the end, you should be able to:
- Use grounding and bonding terminology precisely
- Trace ground-fault current back to its source
- Explain service bonding and downstream isolation
Key idea: The earth is not the normal low-impedance fault-current path that trips a branch-circuit breaker.
Terminology
- Grounding
- Bonding
- Grounded conductor
- Equipment grounding conductor
- Grounding electrode conductor
- Grounding electrode system
- Effective ground-fault current path
Trace a fault
Imagine an ungrounded conductor contacting a metal appliance chassis. The equipment grounding and bonding path carries fault current back toward the source. A sufficiently low-impedance path allows enough current to flow for the overcurrent protective device to open promptly.
Neutral and equipment grounding conductors are connected at the service disconnecting means, but they are normally isolated downstream. Reconnecting them downstream can place normal return current on metal enclosures and grounding paths.
Code-navigation exercise
Using the currently adopted NEC and applicable local amendments, locate the definitions for bonding, grounded conductor, grounding conductor, and effective ground-fault current path. Write each reference in your notes.