Circuit Breaker Keeps Tripping? How to Diagnose the Cause A circuit breaker that keeps tripping is not being faulty for no reason — it's reporting a fault. The way it trips is the diagnosis: instantly with no run time points to a short circuit or earth fault, a delay of seconds to minutes points to overload or heat, and a trip the moment a motor starts points to inrush current outrunning the breaker's magnetic setting. Read the pattern correctly and you can usually name the cause before you've opened the panel. This guide covers the eight most common reasons a breaker trips repeatedly, how each one actually presents, and the checks that confirm it — so you fix the real fault instead of resetting the same breaker every shift until something worse fails. Don't just keep resetting it. A breaker that trips repeatedly is doing its job. Repeatedly forcing it closed against a real fault stresses the contacts and mechanism and, on a short circuit or earth fault, is a genuine shock and fire risk. Isolate, diagnose, and only re-energise once you know what tripped it. Talk to Our Expert Team How a Circuit Breaker Actually Decides to Trip A standard thermal-magnetic breaker is watching the current through it in two completely different ways at once, and that's the key to reading its behaviour. A bimetal strip bends as it heats up, and enough sustained current bends it far enough to trip — slowly, over seconds to minutes, which is exactly what a real overload looks like. Separately, a small solenoid reacts to a sudden surge of current by physically snapping a plunger in, tripping in milliseconds — built to catch a short circuit before it does real damage. Both paths pull the same trip bar, which releases a spring-loaded latch and snaps the contacts open. Once you know which of the two paths fired, you already know roughly what kind of fault you're chasing. Current flows through the breaker and is monitored by two parallel paths: a thermal bimetal element that trips slowly on sustained overload, and a magnetic solenoid that trips instantly on a current spike. Either path releases the trip bar and latch, snapping the contacts open. Current flows through the breaker Thermal element (bimetal) Bends under sustained overload — trips in seconds to minutes, faster the bigger the overload. Magnetic element (solenoid) Reacts to a sudden current spike — trips in milliseconds, built to catch a short circuit fast. Trip bar releases the latch Contacts snap open — circuit interrupted Trip Mechanism Glossary Element What It Does Thermal element Bimetal strip that bends with heat, providing the slow, inverse-time overload trip Magnetic element Solenoid that reacts to a current spike, providing the near-instant short-circuit trip Trip bar The shared linkage either the thermal or magnetic element can push to trigger a trip Latch Spring-loaded catch that holds the contacts closed until the trip bar releases it Contacts Open the instant the latch releases, physically interrupting the circuit Trip curve The published time-vs-current graph (Type B/C/D) that sets how much overcurrent it tolerates before tripping, and how fast 8 Causes of a Circuit Breaker Tripping Repeatedly 1 Overload — Current Draw Exceeds the Trip Curve The single most common cause, and the easiest to confirm: too much genuine load is running on the circuit for its rated current. It typically trips after the circuit has been running fine for a while — minutes under a heavy overload, longer under a marginal one — because the thermal element has to heat up before it bends far enough to trip. Clamp-meter the actual current at the panel while the circuit is under its normal working load; if it's sitting above the breaker's rated current, you've found it, and the fix is either reducing the load or moving to a correctly sized circuit and breaker, not a bigger breaker on the same undersized cable. 2 Short Circuit — Line-to-Line or Line-to-Neutral Fault This is the magnetic element doing exactly what it's designed for: an instant trip, with no run time at all, often the moment the breaker is reset. It means damaged insulation, a trapped or pinched cable, or a failed component is letting current jump between conductors it shouldn't. Don't keep resetting it — isolate the circuit and insulation-test (megger) it before re-energising, and inspect for obvious damage at recent work points, cable glands, and connection boxes first. 3 Earth Fault Tripping an RCD/RCBO, Not the Breaker Itself If there's residual current protection on the circuit, check which device actually tripped before assuming it's the breaker — a leakage to earth from damp cabling, a failing heating element, or a compromised appliance will trip the RCD/RCBO while the breaker itself would happily carry the load all day. Isolate branches one at a time and retest to isolate which downstream circuit is leaking, rather than replacing the protective device that's correctly doing its job. 4 Motor or Transformer Inrush Exceedin…