Troubleshooting guide

Why Does a Circuit Breaker Keep Tripping?

Overload, short circuit, ground fault, inrush, loose connections and heat: how to tell the causes apart from how and when the breaker trips.

Electrical & Power · Last reviewed October 15, 2026

A breaker trips for a reason, so the first question is how it tripped. A breaker that trips after minutes or hours behaves differently from one that trips instantly, and the difference points to the cause.

Do not keep resetting a breaker that trips repeatedly, and never replace it with a larger one to stop the tripping. The breaker protects the wire. Diagnosis on live circuits belongs with a qualified electrician.

How it trips	Likely cause	What to check
After minutes or hours, with the load running	Overload: the circuit carries more current than the breaker rating over time	Total connected load against the breaker rating; continuous loads are limited to 80% of the rating in most code applications
Instantly, on closing or on starting a load	Short circuit, or a large inrush (motors, transformers, some power supplies)	Wiring damage, a failed load, or inrush against the breaker's instantaneous setting or curve
Instantly or after a short delay, GFCI or ground-fault type	Ground fault: current leaking to ground through damaged insulation or moisture	Damp locations, damaged cords, appliance leakage. Disconnect loads one at a time
AFCI breaker trips with no overload	Arcing from a damaged or loose conductor, or a device that mimics arcing	Loose terminations, damaged cable, and which device triggers it
Trips more in hot weather or in a full panel	Breaker heating from a loose connection or high ambient temperature	Terminal tightness; heat marks; thermal imaging by a qualified person
Trips with no apparent load	Worn breaker, loose connection or a fault that appears intermittently	Connections at the breaker and the load; replace a breaker that has been tripped many times

A quick overload check

A 20 A breaker feeds a 120 V circuit. For a continuous load the usual limit is 80% of the rating.

Continuous limit = 0.80 × 20 A = 16 A.
At 120 V, 16 A is 1,920 W.
Loads totaling 2,400 W on that circuit draw 2,400 ÷ 120 = 20 A. That is right at the rating and well over the continuous limit, so a trip after some time is expected.

Write a useful problem statement

Breaker type and rating, and the circuit it feeds.
How it trips (instantly or after a delay) and what was running.
When it started, and what changed.
What was tried, with the result.

A second example: two loads on one circuit

A 1,800 W space heater and a 900 W vacuum cleaner share a 120 V, 20 A circuit.
Total = 2,700 W ÷ 120 V = 22.5 A, which is over the 20 A rating, so the breaker trips after some time.
Moving the vacuum to a different circuit leaves 1,800 ÷ 120 = 15 A on the first one. That is below 20 A, but a continuous load should stay at or below 80% of the rating, which is 16 A here, so 15 A passes.

Preventive checks

Label every circuit and keep a record of what is on it.
Keep continuous loads at or below 80% of the breaker rating.
Have terminations checked and re-torqued by a qualified person on a schedule, and look for heat marks.
Replace a breaker that has tripped many times under fault conditions, or that feels hot in normal use.

Related tools and labs

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Questions

Can I use a bigger breaker?

No. The breaker rating must not exceed the wire's ampacity. A larger breaker lets the wire overheat before it trips.

Why does a motor trip a breaker on starting?

A motor draws several times its running current for a moment. A breaker with the wrong curve or too low a rating trips on that inrush even though the running current is fine.

How many trips is too many?

There is no fixed count, but a breaker that has tripped repeatedly under fault conditions may no longer trip at its rating and should be checked or replaced.

What is the difference between a thermal and a magnetic trip?

The thermal element responds slowly to a sustained overload by heating a bimetal strip. The magnetic element responds immediately to a very large current such as a short circuit.

Can a loose connection trip a breaker?

It can cause heating that makes a thermal breaker trip, and a loose connection can also create arcing. Both are reasons to have the terminations checked.

When should I call an electrician?

When a breaker trips repeatedly, trips instantly after a reset, feels hot, smells of burning, or shows scorch marks. Do not keep resetting it.

Educational material. Examples use simplified, hypothetical inputs and are not a design, a construction document or professional engineering advice. Confirm requirements with the codes and standards adopted where the work is built and with a licensed engineer.

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