Apprentice path · Stage 8: Equipment and faults · Lesson 28

Open, short and ground fault

Three different faults: one breaks the path, one creates a path that should not exist, and one connects a live conductor to something grounded.

Why this matters on the job

They look similar from the outside -- something stopped working -- and they need completely different fixes. Naming the fault correctly is most of the diagnosis.

How to think about it

  1. An open interrupts an intended path -- the circuit is broken where it should be continuous.
  2. A short creates an unintended low-resistance path -- current takes a shortcut it was never meant to have.
  3. A ground fault connects an ungrounded conductor to a grounded path.

Worked through

A broken wire and a wire faulting to a metal enclosure are not the same problem. The broken wire is an open: the path is gone and nothing runs. The fault to the enclosure is a ground fault: the path is still there, plus a new one to grounded metal, and now the enclosure is part of the circuit.

Check yourself: Equipment has stopped working and its metal enclosure is energized. Open, short, or ground fault?

Answer: A ground fault -- an ungrounded conductor has found a connection to a grounded path.

An open would simply stop the equipment and leave the enclosure dead. The enclosure being energized means a live conductor has made contact with grounded metal, which is what a ground fault is.

Watch out for: Calling everything a short. A short and a ground fault both create current where you did not want it, but they are different faults with different consequences and different things to look for.
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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.