Grounding connects a system or equipment to earth. Bonding connects conductive parts together. A ground rod connects to earth. A bonding jumper connects metal parts so fault current can return to the source and operate a breaker or fuse. On an exam, identify which job the conductor performs before choosing a sizing table.
Watch: grounding and bonding explained
Follow JCR’s Article 250 lesson with your 2020 NEC open. Identify the grounding and bonding paths before working the conductor-sizing questions.
Bonding and Grounding Explained - Article 250 NEC 2020Watch JCR’s lesson on YouTube ↗
This explanation uses 2020 NEC Article 250, especially 250.4(A), 250.24 and 250.32.
What grounding does
Connecting the system to earth helps limit voltage from lightning, surges and accidental contact with higher-voltage lines. It also stabilizes voltage to earth during normal operation.
The grounding electrode system may include qualifying metal water pipe, a concrete-encased electrode, ground rods and other electrodes. The conductor connecting to that system is the grounding electrode conductor, or GEC.
What bonding does
Bonding joins metal parts so they form an electrically continuous path. In a typical grounded system, that path connects equipment back to the supply’s grounded conductor at the permitted bonding point.
Consider a damaged hot conductor touching a metal motor enclosure. A suitable equipment grounding and bonding path carries fault current back to the source. The low-impedance return path allows enough fault current to operate the breaker or fuse. Without that path, the enclosure can remain energized.
Trace the whole fault loop: transformer, hot conductor, damaged enclosure, equipment grounding path, service bond and transformer. Earth has too much impedance to serve as the effective ground-fault current path. That is why a ground rod alone cannot replace the required equipment grounding path.
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Bonding & Grounding CE classes
Already licensed? Study Article 250 with a JCR instructor and earn continuing-education credit. See upcoming dates and state approvals on our CE page.
See grounding & bonding CE classesLive classes teach the 2020 NEC. Check your state’s exam requirements before choosing a course. NC prep includes NC business and law. For another state, also study any business-and-law material required for your license. Need a code book? JCR carries the 2020 NEC softbound book.
Three conductors students mix up
| Conductor or jumper | Typical job | 2020 NEC starting point |
|---|---|---|
| Equipment grounding conductor, EGC | Connects equipment metal to the fault-current return path | 250.122 for wire sizing, generally tied to the upstream protective device |
| Grounding electrode conductor, GEC | Connects the system to grounding electrodes | 250.66, including electrode-specific rules |
| Main bonding jumper | Joins the grounded conductor to the equipment grounding path at the service | 250.28 and 250.102(C) |
For a wire-type equipment grounding conductor on a 100-amp breaker, start at Table 250.122. For a grounding electrode conductor, start at 250.66 and check the rule for that electrode. See worked examples for equipment grounds, grounding electrode conductors and the main bonding jumper.
Why neutral and ground separate after the service
In a typical new feeder-supplied panel, isolate the neutral from the enclosure and equipment grounding bar. Bonding them again can put normal neutral current onto metal paths intended for equipment grounding.
A separate building generally needs its own grounding electrode system as well as the required equipment grounding path with the supply. Adding rods doesn’t replace that path. Article 250 contains limited exceptions for specific arrangements, including some existing installations. Don’t turn an exception into a rule for new work.
Quick exam check
A feeder supplies a detached garage. Someone proposes two ground rods instead of an equipment grounding conductor. Does that solve the fault-path requirement for a typical new feeder?
See the answer
No. Earth is not the effective ground-fault current path. The electrode system and equipment grounding path have separate jobs. Read 250.32 for the separate-building requirements.
Common questions
Does an equipment ground carry current normally?
It isn’t intended to carry normal load current. It provides a path for fault current and helps connect exposed conductive parts.
Is the neutral a ground wire?
No. The neutral is a grounded circuit conductor and can carry normal load current. It isn’t interchangeable with an equipment grounding conductor.
Examples use the 2020 NEC. References checked October 25, 2026.
