Checked against primary sources 2026-08-24

Grounding and bonding are two different jobs

The trade uses these words interchangeably. The code does not. One sentence in Article 250 settles most of the questions people get wrong.

Test yourself: 25 free questions on this topic

The sentence

Article 250 contains one line that answers more exam questions than anything else in it. Under Use of the Earth, the code states flatly that the earth shall not be considered an effective ground-fault current path (NEC 250.4(A)(5)(c)). Open your own code book and read that sentence in place.

Sit with it. A ground rod does not clear a fault. Dirt is not a conductor in any useful sense at the currents a breaker needs to see. If an answer choice implies fault current travels through the earth back to the source, it is wrong, and it will be offered on more than one item.

In the 2026 edition that sentence has its own lettered home. Effective Ground-Fault Current Paths at 250.4(A)(5) breaks into three pieces: opening the overcurrent protective device, carrying the ground-fault current, and the use of the earth. Reading the three in order tells you what the path is for before it tells you what the earth is not.

What the two words mean in Article 100

Both terms are defined, both definitions are one line long, and neither says what most people think it says.

• Bonded, or bonding, means connected so as to establish electrical continuity and conductivity. Nothing in it mentions the earth.
• Grounded, or grounding, means connected to ground, or to a conductive body that extends the ground connection.
• Ground is defined as the earth. Two words, and it is the whole reason the first two definitions are not the same thing.

Read them together and the distinction is structural rather than a matter of emphasis. Bonding is about continuity between conductive parts. Grounding is about a connection to the planet. A conductor can do both jobs, which is why the words blur in the field, but an exam item is always testing one of them.

The equipment grounding conductor is the piece that gets misread most often, because its name has grounding in it. Article 100 defines it as part of the effective ground-fault current path, connecting normally non-current-carrying metal parts together and back to the system grounded conductor or the grounding electrode conductor. It is a bonding conductor with a grounding name.

So what is the ground rod for

The earth connection does a real job. It is just not the job most people assume.

A grounded system is connected to earth to limit the voltage the system can be pushed to by lightning, by line surges, or by unintentional contact with a higher-voltage line, and to hold the system stable with respect to earth in normal operation (NEC 250.4(A)(1)).

Notice what is absent. Nothing in that list is clearing a fault. Clearing a fault is a different job, done by different hardware, and the electrode is not involved in it.

Bonding is what clears the fault

Bonding is connecting the metal together. Conduit to enclosure, enclosure to equipment grounding conductor, all of it back to the source through metal.

That metal path is what carries fault current. The code asks it to be a low-impedance circuit that will operate the overcurrent protective device, and to be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point where a fault occurs back to the supply source (NEC 250.4(A)(5)).

When a hot conductor touches a metal box, the fault current runs through bonded metal back to the source and trips the breaker. The electrode is a spectator for that entire sequence.

Grounding connects to earth. Bonding connects metal to metal. Bonding is the one that saves somebody.

Sorting an item in one read

The useful question is not which word appears in the item. It is which job the thing in the item is doing.

• If the conductor or connection ends on an electrode, or ties electrodes to each other, it belongs to the grounding electrode side and it sizes from 250.66.
• If it carries fault current back toward the source, it belongs to the fault-path side, and depending on where it sits that is 250.122, Table 250.102(C)(1), or the bonding methods at 250.92(B).
• If the item is about continuity across a fitting, a reducing washer, an expansion joint or a concentric knockout, it is a fault-path question no matter what the parts are called.

Sorting on the name fails, and it fails in the direction that costs you the answer. 250.66 sizes "bonding jumpers for connection of grounding electrodes", and 250.64(E)(3) sizes a bonding jumper from the grounding electrode conductor it encloses. Both are called bonding jumpers. Both are sized on the electrode side. A candidate who sorts on the word reaches for Table 250.122 and gets a number that is not on offer.

Run it the other way and it holds. A supply-side bonding jumper at 250.102(C) has bonding in its name and sizes on the fault-path side. A bonding bushing at a service raceway sizes on the fault-path side. Two names that point one way, four items that sort the other way on the job. Use the job.

Two traps built into the wording

The first is objectionable current. Where multiple grounding or bonding connections produce current where it should not be, 250.6(B) offers four alterations, and the first of them is to discontinue one or more but not all of those connections. Read the limit in that sentence. Not all.

Then read the section that closes the door behind it. Electronic equipment may not be operated on a circuit that has no equipment grounding conductor, and noise or data errors in electronic gear are not the objectionable current this section is about (NEC 250.6(D)). Current from a ground fault, and current from connections the code requires, are not objectionable either (NEC 250.6(C)).

So the field habit of lifting a ground to cure a hum has a subsection written specifically to forbid it.

The second is the isolated ground. An isolated equipment grounding conductor is permitted, and an informational note under the section says plainly that using one does not relieve the requirement for an effective ground-fault current path (NEC 250.96(B)). The insulated conductor is in addition to the fault path, never instead of it.

How to study Article 250

It is long and it is dense, and reading it front to back does not work well.

Read the performance requirements at the front first. They explain what the rest of the article is trying to accomplish, and most of the detailed sections make sense once you know which of the two jobs they serve.

Then, for any section you are working through, ask one question: is this conductor headed for the earth, or headed back to the source? Nearly every rule in the article answers that, and the ones that answer "back to the source" are the ones that matter when something goes wrong.

What this page cites

• NEC 250.4 Performance requirements. 250.4(A) is grounded systems, 250.4(B) is ungrounded systems, and the two run in near-identical wording. Read which one the item is about. source
• NEC 250.4(A)(5) Effective Ground-Fault Current Paths. Split into (a), (b) and (c) for the 2026 edition by NFPA CMP-5 second revision 8333. source
• NEC 250.6 Objectionable current, the four permitted alterations, and the limits on all of them.
• NEC 250.92 Bonding at services, including the methods and the locknut question.
• NEC 250.96 Bonding other enclosures, including isolated grounding circuits.
• NEC 250.66 Sizing on the grounding electrode side, including the bonding jumpers used to connect electrodes.