Why does my circuit breaker keep tripping?
Short answer: Most repeat trips come from an overloaded circuit, a short circuit, a ground fault, or, on AFCI breakers, an arc fault. A 15-amp, 120-volt circuit handles 1,800 watts in total, so a 1,500 W space heater uses most of it. Spread big loads across circuits. Call a licensed electrician if it keeps tripping.
What makes a circuit breaker trip?
A breaker is a safety switch. It cuts power when current rises to a level that could overheat wiring or start a fire. Repeat trips usually come from one of four causes.
| Cause | What is happening | Typical clue |
|---|---|---|
| Overloaded circuit | Devices draw more current than the circuit is rated for | Trips after a heater, hair dryer, or microwave turns on |
| Short circuit | A hot wire touches another conductor | May come with a burning smell or scorch marks |
| Ground fault | A hot wire contacts the ground wire or a metal box | Trips again soon after reset |
| Arc fault (AFCI breakers) | Sparking from damaged, overheated, or stressed wiring or devices | AFCI breaker trips; may follow a nail or screw driven into a wall |
ESFI says arc faults are caused by “damaged, overheated, or stressed electrical wiring or devices.” Its examples include older wires that become frayed or cracked, a nail or screw that damages a wire behind a wall, and overburdened outlets or circuits.
How many watts can a 15-amp or 20-amp circuit handle?
Power equals voltage times current: watts = volts × amps. On a standard 120-volt household circuit:
| Breaker size | Formula | Maximum load |
|---|---|---|
| 15 A | 15 A × 120 V | 1,800 W |
| 20 A | 20 A × 120 V | 2,400 W |
That limit covers everything on the circuit, not each outlet. One circuit often feeds several outlets and lights.
Why does my space heater trip the breaker?
Many portable space heaters are rated 1,500 watts on high; check the label. On 120 volts that is 1,500 ÷ 120 = 12.5 amps. That is about 83% of a 15-amp circuit, leaving only 300 W for everything else.
Add a 1,200 W appliance on the same circuit and the total is 2,700 W, or 22.5 amps. That is over both a 15 A and a 20 A circuit. See what a space heater costs to run, or check any appliance with the appliance electricity cost calculator.
What should I do when the breaker trips?
These steps are for an ordinary overload only. If you notice any warning sign in the next section, leave the breaker off and call a licensed electrician.
- Unplug or switch off devices on the dead circuit, especially heaters, hair dryers, and kitchen appliances.
- Reset the breaker once. Find the handle in the middle or “off” position. Push it fully to OFF, then firmly back to ON.
- Plug things back in one at a time. If it trips when one device comes on, that device or the total load is the likely cause.
- Spread high-watt loads across different circuits. Don’t run a space heater and a hair dryer on the same circuit.
- Inspect cords. CPSC says not to use equipment or cords that are damaged.
ESFI advises against overloading outlets. It says to use extension cords only temporarily, and never with space heaters or air conditioners. If you need more capacity, have an electrician add circuits or outlets.
When should I call an electrician?
ESFI lists circuit breakers that trip repeatedly as a warning sign and says to “contact a qualified electrician immediately.” CPSC lists breakers that need resetting frequently as a hazard sign. Call a licensed electrician if you notice:
- A breaker that keeps tripping, or won’t reset or stay on
- Tripping with nothing plugged into the circuit
- A burning smell or the odor of overheated plastic
- Hot outlets, outlet covers, or switch plates
- Dim or flickering lights
- Sizzling or buzzing sounds from outlets or the panel
Don’t keep resetting a breaker that trips again right away. Leave it off until an electrician checks it.
Can I just put in a bigger breaker?
No. Never replace a breaker with a larger one. A breaker’s rating is matched to the wire it protects. A bigger breaker lets more current flow than the wire can safely carry, so the wiring can overheat before anything trips.
Never tape, wedge, or hold a breaker in the ON position. That disables the protection.
Quick answers
Is it dangerous if my breaker keeps tripping? The breaker is doing its job, but repeated trips are a warning sign. ESFI and CPSC both treat it as a reason to have an electrician check the system.
How many space heaters can run on one 15-amp circuit? One. A 1,500 W heater draws 12.5 of the 15 amps. Two would draw 25 amps.
Why does my breaker trip with nothing plugged in? That points to a wiring fault rather than an overload. Leave it off and call a licensed electrician.
Can a bad breaker cause tripping? It can, but only a licensed electrician should diagnose or replace one. Never swap in a larger size.