Bonding vs grounding
Grounding connects the electrical system to the earth as a reference; bonding ties all the conductive parts together so a fault has a low-impedance path back to its source. The two words get used as if they mean the same thing. They do not, and the difference is the whole reason a ground fault trips a breaker.
What each one is for
Think about where fault current actually wants to go. When a hot conductor touches something it should not, the current is trying to get back to the source it came from — the transformer — not into the ground under your feet. Bonding gives it that road home: every metal enclosure, raceway and frame is tied together and back to the source, so a fault becomes a big current on a low-impedance path, and a big current is exactly what a breaker is built to notice and cut off.
Grounding — the connection to earth — is doing a different job. It pins the system to a stable voltage reference and gives lightning and utility surges somewhere to go. Earth itself is a mediocre conductor; you cannot rely on the dirt to carry enough current to trip anything. That is why a system that is "grounded" but not properly bonded is dangerous: the reference is there, but the fault-clearing path is not.
Keep the two jobs separate in your head — reference to earth on one side, a solid low-impedance tie back to the source on the other — and the terms stop blurring. Which specific conductors do which, and how they are sized and identified, is set by the code and stays in the code book.
Questions people ask
Is bonding the same as grounding?
No. Grounding connects the system to earth as a reference. Bonding ties conductive parts together so they sit at the same potential and a fault has a low-impedance path back to the source. They are related jobs that people say interchangeably, but they are not the same thing.
Why does bonding trip the breaker but grounding does not?
Because the fault current that operates a breaker wants to return to its source, not to the dirt. Bonding provides that low-impedance return path, so a ground fault becomes a large current the breaker can see and clear. Earth is a poor conductor by comparison and will not carry enough to trip anything.
What does the earth connection actually do, then?
It holds the system at a stable voltage reference and helps with things like lightning and utility surges. It is about reference and transient events, not about clearing everyday faults — that is bonding's job.
Related
- AFCI vs GFCI
- 240 V receptacle wiring — where the bond shows up in a diagram.
- Back to the glossary
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