Wireman · Breaker keeps tripping: troubleshooting for electricians · 2023 NEC ·

Breaker keeps tripping

Find out whether it’s an overload, a short, a ground fault or the breaker itself.

Before you start

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How it works

A standard breaker trips two ways. The thermal part trips on overload: too much current for too long, so it takes seconds to minutes. The magnetic part trips instantly on a short circuit or ground fault, when current jumps to hundreds of amps. When it trips tells you which one you’re dealing with.

Step by stepFull flowchart

Every question and answer in this guide. Tap “Step by step” to walk through it.

When does it trip?
- The instant I reset itUnplug every cord-connected load and turn off every switch on that circuit, then reset. Does it still trip instantly?
  - Still trips instantlyTest: Test the wiring for a shortExpect: OL (open) on both, or a very high reading.
    - Hot to ground near 0 ΩHot shorted to ground in the wiring
    - Hot to neutral near 0 ΩHot shorted to neutral
    - Both read OL (open)What kind of breaker is it?
      - Standard breaker (no test button)The breaker or its bus connection is bad
      - AFCI, GFCI or dual functionAn AFCI or GFCI protection trip, not an overload
    - Some ohms (roughly 5–200 Ω)Something is still connected
  - Holds nowPlug things back in and turn them on one at a time. Does it trip when one particular thing comes on?
    - Yes, one item trips itA fault inside the appliance or its cord
    - It trips once several are onTest: Measure the circuit currentExpect: Below 80% of the breaker rating for loads that run for hours (16 A on a 20 A).
      - At or above the breaker ratingOverload: too much on one circuit
      - Well below rating, but the breaker or wire is hot or discoloredA loose or failing connection at the breaker
      - Well below rating, nothing hotA weak breaker
    - Everything works nowAn intermittent fault: a loose connection, damaged cable or a load that only faults sometimes
- When one thing turns onIs that load a motor or compressor?
  - Yes, it has a motorTest: Compare the load to the breakerExpect: Running amps at or below the nameplate, and the nameplate below about 80% of the breaker.
    - Running amps above nameplateThe motor is drawing too much current
    - Normal amps, but the breaker is small for itThe circuit is too small for the load
    - Normal amps, breaker is sized rightStarting current on a borderline circuit
  - No (heater, kettle, microwave, hair dryer)What else is on that circuit when it trips?
    - Other heavy loads are on tooOverload: too much on one circuit
    - It trips even when it’s the only thing onA fault inside the appliance or its cord
- After it runs a whileTest: Measure the circuit currentExpect: Below 80% of the breaker rating for loads that run for hours (16 A on a 20 A).
  - At or above the breaker ratingOverload: too much on one circuit
  - Well below rating, but the breaker or wire is hot or discoloredA loose or failing connection at the breaker
  - Well below rating, nothing hotA weak breaker
- Randomly, no patternIs it an AFCI, GFCI or dual-function breaker?
  - YesAn AFCI or GFCI protection trip, not an overload
  - No, standard breakerDoes it happen more in rain, humidity or when sprinklers run?
    - YesMoisture causing a ground fault
    - No patternAn intermittent fault: a loose connection, damaged cable or a load that only faults sometimes