Rule 15 of 40 · Chapter III — Grounding, Bonding, and Protection
Ground and bond are not the same
Why this rule exists
The two words get used interchangeably and mean different things. Bonding connects all the metal that is not meant to be energized, enclosures, conduit, equipment frames, together with a low-impedance path, so fault current has an easy route back to the source and trips the breaker fast. Grounding ties that system to earth, mainly to stabilize voltage and handle surges and lightning. It is bonding, not the earth connection, that clears a ground fault; soil is too high-resistance to trip a breaker alone. Confusing them yields installations that look safe and are not.
In practice
Provide a continuous, low-impedance equipment grounding (bonding) path from every device back to the source neutral-ground bond, sized to carry fault current. Keep grounding and grounded (neutral) conductors separate everywhere downstream of the main bonding jumper; bond them at exactly one point, the service. Bond metal enclosures, boxes, and conduit. Drive and connect grounding electrodes for the earth connection, but never rely on earth as the fault-clearing path. When you replace a device, restore its bonding jumper; do not leave the ground pin floating.
When it doesn't apply
The single neutral-to-ground bond location differs for separately derived systems like generators and transformers, where a new bond is made at that source. Isolated-ground receptacles and sensitive-equipment schemes have specific rules. These are the places people get it subtly wrong; if the scheme is not clear, verify against the code or ask a qualified electrician before energizing.