The short answer: Grounding and bonding are different jobs. Grounding connects the electrical system or equipment to the earth, mainly to stabilize voltage and limit the effects of lightning and surges. Bonding connects metal parts together so they form a low-impedance path that carries fault current back to the source and trips the overcurrent device. The earth is not an effective fault-clearing path, so the bonding path, not the ground rod, is what clears a fault. These requirements live in NFPA 70, the National Electrical Code (NEC), Article 250, a consensus standard; OSHA separately requires the path to ground to be permanent, continuous, and effective under 29 CFR 1910.304(g)(5).
What is the difference between grounding and bonding?
Grounding is a connection to earth; bonding is a connection between metal parts to make them electrically continuous. NEC Article 250 keeps them separate because they do separate work, and the everyday habit of calling everything "the ground" hides a difference that decides whether a fault clears. Grounding references the system to the earth and helps limit the voltage imposed by lightning, line surges, and unintentional contact with higher-voltage lines, and it stabilizes the voltage to earth during normal operation. Bonding joins the non-current-carrying metal parts of the installation, the enclosures, raceways, and equipment frames, so that if an energized conductor faults to metal, current has a low-impedance route back to its source.
The reason the distinction is not academic is that these two functions fail differently. A perfectly grounded system with poor bonding can leave a metal enclosure energized during a fault, because the fault current cannot find a low-impedance path back to the source to operate the breaker. A well-bonded system with a marginal earth connection still clears faults. Naming the parts correctly is the first step toward installing them correctly.
Why isn't the earth a fault-clearing path?
Because the resistance of the earth is far too high to pass enough current to trip a breaker, so the fault path has to be an engineered conductor, not the ground. This is the single most consequential idea in Article 250: an effective ground-fault current path is a low-impedance conductive route, deliberately installed, that allows enough fault current to flow to operate the overcurrent protective device. Driving a ground rod does not create that path. The rod connects to earth, which stabilizes voltage and handles surges, but earth resistance is orders of magnitude too high to carry the hundreds or thousands of amps needed to open a breaker quickly.
That means the metal path back to the source is what protects people from a faulted enclosure. When a hot conductor contacts a bonded metal box, the bonding and equipment grounding conductors carry the fault current back to the source, the current spikes, and the breaker trips, deenergizing the box in a fraction of a second. Remove or interrupt that bonded path and the box can sit energized at line voltage while the breaker never sees enough current to trip, waiting for a person to complete the circuit. OSHA codifies the same principle in 29 CFR 1910.304(g)(5), which requires that the path to ground from circuits, equipment, and enclosures be permanent, continuous, and effective.
What are the key components and what does each do?
Article 250 assigns each conductor a specific role, and mixing them up is where field mistakes start. The grounded conductor, the equipment grounding conductor, the bonding jumper, and the grounding electrode conductor are not interchangeable, even though all four are commonly called "grounds." The table separates them.
| Component | What it does |
|---|---|
| Grounded conductor (often the neutral) | A current-carrying conductor intentionally connected to ground at the service; completes the normal circuit and is not the same as a grounding conductor |
| Equipment grounding conductor (EGC) | Bonds non-current-carrying metal parts, raceways, and enclosures together and back to the source, forming the low-impedance fault path |
| Main bonding jumper | Connects the equipment grounding conductor system to the grounded (neutral) conductor at the service disconnect, the point where the fault path ties to the source |
| Grounding electrode conductor (GEC) | Connects the grounding electrode system (rods, water pipe, building steel) to the service, establishing the earth reference |
The main bonding jumper deserves particular attention because it is where grounding and bonding meet. It is the connection, made only at the service disconnect, that ties the equipment grounding system to the grounded conductor so that fault current returning on the metal path has a route back to the source. Made in the wrong place, for example downstream at a subpanel, it creates parallel neutral paths and puts current on metal that should never carry it. Made correctly and only once, it is what lets a fault on any bonded enclosure find its way home and trip the breaker.
The grounding electrode side of the system does the other job. The grounding electrode conductor connects the service to the grounding electrode system, the rods, metal underground water pipe, and building steel that establish the earth reference, and Article 250 sizes it from the service conductors rather than from the overcurrent device, because its purpose is voltage stabilization and surge handling, not fault clearing. That is why the two paths are sized on different logic: the equipment grounding conductor is sized to carry fault current fast enough to trip a breaker, while the grounding electrode conductor is sized to reference the system to earth. Treating them as the same "ground" is how an installer ends up with an earth connection that is fine and a fault path that is not.
Why does this matter for the person doing the install?
Because the difference between grounding and bonding is the difference between an installation that protects the next person to touch it and one that looks finished but is not safe. An installation can pass a casual visual check, have a ground rod, and still leave enclosures that will energize during a fault if the bonding path is loose, undersized, or interrupted. The failure is invisible until the fault happens, and then it is a shock or electrocution hazard rather than a tripped breaker.
So the practical discipline is to treat bonding continuity as a life-safety connection, not a cosmetic one. Verify that equipment grounding conductors and bonding jumpers are continuous and tight, that the main bonding jumper is in the one correct location, and that the path to ground is, in OSHA's words under 1910.304(g)(5), permanent, continuous, and effective. NEC Article 250 is a consensus standard and its numbering is detailed, but the idea underneath it is simple and worth carrying to every job: ground to the earth for stability and surges, bond the metal together to clear the fault, and never rely on the earth to do the bonding conductor's job.
