Apprentice path · Stage 4: Finding your way around the code book · Lesson 17

Grounded, grounding, bonded

Three words that sound almost identical name three different things, and mixing them up changes what you are talking about entirely.

Why this matters on the job

These get used interchangeably on site all the time, and they are not interchangeable. In an exam question, and in a fault, the difference is the whole answer.

How to think about it

  1. Grounded conductor: a conductor intentionally connected to ground -- often a neutral. It is a normal current-carrying conductor.
  2. Equipment grounding: provides a conductive path for fault current.
  3. Bonding: joins conductive parts together so they are electrically continuous.

Worked through

Think about what each one is for. A grounded conductor does a job in normal operation. An equipment grounding conductor does nothing in normal operation and everything during a fault -- it is the path that lets enough current flow to trip the protection. Bonding is about continuity: making separate metal parts behave as one piece so there is no difference of potential between them.

Check yourself: A metal enclosure is driven into the earth with a ground rod. Is that an effective ground-fault current path?

Answer: No. Earth alone is not an effective ground-fault current path.

Fault current has to get back to its source to trip the protection, and the earth is too high a resistance to carry enough of it. That is what the equipment grounding conductor is for -- a low-resistance path back, not a path into the dirt.

Watch out for: Assuming "it is grounded" means "it is safe". Grounded, grounding and bonded are three different statements, and only one of them is about a fault path.
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Written from the owner's poster for this lesson. Nothing added beyond what the poster states.

Written for Texas apprentices as free study material. The Texas apprentice licence is an application, not an exam (Occupations Code 1305.161), and nothing here counts as apprenticeship hours or continuing-education credit. VoltMark is not affiliated with, endorsed by, or sponsored by NFPA, PSI, TDLR, or any state or local licensing authority. Always follow your employer's safety programme and your supervising electrician.