Grounding, Bonding, and Overcurrent Protection
Grounding versus bonding
This domain rewards precision in language. Grounding connects the electrical system to earth; bonding connects metal parts together to ensure they remain at the same potential. The grounded conductor (neutral) carries current in normal operation; the grounding conductor does not, except during a fault. Understand the grounding electrode system, the main bonding jumper, equipment grounding conductors, and the rule that the neutral is bonded to ground only at the service, not at subpanels.
Overcurrent protection
Know the types of overcurrent devices, their ratings and interrupting capacity, and the requirement that devices be selected for the available fault current. Understand series ratings, coordination, and the difference between overload and short-circuit protection. Review the rules for tap conductors and the next-size-up allowance.
Traps in questions
Frequent distractors: bonding the neutral at a subpanel, using the neutral as an equipment ground, sizing the grounding electrode conductor by ampacity, and ignoring interrupting rating. Another trap is confusing ground-fault protection of equipment with personnel protection.
Worked example
A subpanel is fed from a main service. Rule of thumb: at the subpanel, keep the neutral and equipment ground separate, and bond the panel enclosure to the equipment ground. The main bonding jumper exists only at the service.
Practice approach
Draw a service-to-subpanel one-line diagram and label every bonding point and grounding connection.