Why does my breaker keep tripping? Overload one and see
A breaker trips for one of three reasons, and each one looks different from the outside. Plug appliances into the circuit below until the breaker gives up, then switch to a short circuit and a ground fault. You'll see which part inside the breaker does the tripping, and why some trips take minutes while others take milliseconds.
By ToborUpdated Nov 1, 20269 min read
Safety first. This page is a learning model of a standard US 120 V household circuit. Resetting a breaker and unplugging things is safe for anyone. Never remove the panel's inner cover (the dead front): the parts behind it stay live even with every breaker off. If you smell burning, see scorch marks, or a breaker trips with nothing plugged in, stop and call a licensed electrician.
Why does a breaker keep tripping? Three reasons
Short answer: a breaker keeps tripping because the circuit is overloaded (too many appliances on it at once), has a short circuit (a hot wire touching neutral), or has a ground fault (current leaking to ground). An overload trips after seconds or minutes; a short or ground fault trips the instant you reset it.
A breaker isn't there to protect your hair dryer. It protects the wire inside your walls. Push too much current through a wire and it heats up; hot enough, and the insulation melts and can start a fire. The breaker cuts power before that happens. It watches for three kinds of trouble, and the tabs in the simulator above match them:
Cause
What's happening
How fast it trips
What to do
Overload
Too many appliances on one circuit. Every one works fine; together they draw more than the wire is rated for.
Seconds to many minutes, depending on how far over
Unplug something. Move big loads to other circuits.
Short circuit
The hot wire touches the neutral (a crushed cord, a loose wire in a box). Current shoots to hundreds or thousands of amps.
Instantly, in under 1/60 of a second
Find and remove the damaged cord or device. If it's in the wall, call an electrician.
Ground fault
Current escapes to ground: through water, a damaged appliance, or a person.
A hot wire touching grounded metal trips any breaker instantly, like a short. A small leak (through water or a person) only trips a GFCI, in about 1/40 of a second.
Unplug the wet or damaged device. Check that wet areas have GFCI protection.
Trips after a while: too much load. Trips instantly: something is broken.
That one distinction tells you where to look, and it's the most useful thing to remember from this page.
How many amps can a 15 or 20 amp circuit handle?
Most household outlet circuits are 15 amps (wired with 14-gauge copper) or 20 amps (12-gauge). Kitchens and bathrooms get 20 amp circuits because that's where the heating appliances live. To find what an appliance draws, divide its watts by 120 volts:
amps = watts ÷ 120
Appliance
Typical watts
Amps at 120 V
Space heater
1,500 W
12.5 A
Hair dryer
1,500–1,875 W
12.5–15.6 A
Electric kettle
1,500 W
12.5 A
Air fryer
1,400–1,700 W
11.7–14 A
Microwave (1,000 W cooking power)
about 1,200–1,500 W
10–12.5 A
Coffee maker
1,000 W
8.3 A
Vacuum
1,000 W
8.3 A
Toaster
900 W
7.5 A
Window AC (5,000 BTU)
500 W
4.2 A
TV
120 W
1 A
Laptop, LED lamp, phone charger
10–65 W
under 0.6 A
Your appliance's nameplate (on the bottom or the cord tag) has the real number. Notice how lopsided the list is: anything that makes heat draws roughly 7 to 15 amps, and everything else barely registers. A 15 amp circuit can run a TV, a laptop and every lamp in the room, but not a space heater and a hair dryer together.
The 80% rule
Electricians don't plan to run a circuit at 100%. The electrical code (NEC) limits a single plug-in appliance to 80% of the circuit's rating, and sizes circuits so loads that run for three hours or more stay under 80% too. That's 12 amps on a 15 amp circuit and 16 amps on a 20 amp circuit. The dashed line on the meter in the simulator marks it. A space heater alone (12.5 A) is already over that line on a 15 amp circuit.
What's inside a circuit breaker
The breaker in the simulator is drawn x-ray so you can watch the parts move. A standard household breaker has two separate ways to trip, and a GFCI breaker adds a third:
Bimetal strip
Two metals bonded together that expand at different rates. Current heats it, it bends, and eventually it pushes the trip bar. It heats up the way the wire in your wall does, which is the point. Handles overloads.
Electromagnet
A coil the current passes through. Normal current barely magnetizes it. A short-circuit surge, typically 5 to 10 times the rating or more, snaps the armature over and trips the breaker instantly. Handles shorts.
GFCI sensor coil
A ring around the hot and neutral wires that measures the difference between current going out and current coming back. More than about 5 thousandths of an amp missing means a leak to ground. Handles ground faults.
Contacts and latch
Whatever trips it, the result is the same: a spring snaps the contacts apart and the handle jumps to the middle position. That's why a tripped breaker looks "half off".
Why one trip takes minutes and another takes milliseconds
Put the two mechanisms together and you get the breaker's time-current curve. The more current, the faster it trips. A little over the rating takes minutes (or never trips at all), and past roughly ten times the rating, the electromagnet takes over and the trip is instant. The orange dot is whatever you've plugged in above; go back and add a heater to watch it slide.
A simplified curve for a 15/20 A thermal-magnetic breaker. Real breakers trip inside a band around this line; check your breaker maker's published curve for exact numbers.
The slow thermal part is deliberate. Motors and compressors pull a big surge for a moment when they start, and a breaker that tripped on every brief spike would be useless. UL 489, the standard US breakers are tested to, requires a breaker to trip within an hour at 135% of its rating. In practice it trips much sooner than that, as the curve shows.
Breaker trips after a few minutes? It's an overload
If the breaker holds for a while and then trips, especially when the same appliances are running, it's almost always an overload. To find it:
Notice what was running. Heater, hair dryer, kettle, microwave, vacuum, window AC. Any two of those on one circuit is a likely culprit.
Map the circuit. Turn the breaker off and walk around: every outlet and light that went dark is on that circuit. Circuits often run between rooms, so a bathroom outlet may share a breaker with a bedroom.
Split the load. Move the heater or the hair dryer to an outlet on a different circuit. That's usually the whole fix.
Don't stack heat. Space heaters run for hours at 12.5 A. Give each one its own circuit, plug it straight into the wall, and never into a power strip or a thin extension cord.
If one appliance alone trips a breaker that has nothing else on it, the appliance may be faulty or simply too big for that circuit (a 1,875 W hair dryer on its highest setting draws 15.6 amps, a little over a 15 amp circuit by itself).
Space heater keeps tripping the breaker?
It's the classic overload. A 1,500 W heater draws 12.5 amps for hours, which is already over the 12 amp all-day limit of a 15 amp circuit. Anything else on that circuit, even a vacuum for a few minutes, tips it over. Give the heater a circuit to itself, plug it straight into the wall, and never run it through a power strip or a light-duty extension cord.
Breaker trips immediately when you reset it? A short or a ground fault
An instant trip is the breaker telling you something is damaged, not overloaded. Try the short circuit tab above and reset the breaker without unplugging the lamp: it trips again before you can blink. Here's how to narrow it down:
Unplug everything on that circuit and turn off its wall switches.
Reset the breaker (OFF, then ON).
If it holds, plug things back in one at a time. The one that trips it is the culprit: look for a crushed cord, a burned plug or water.
If it trips with nothing plugged in, the fault is in the wiring, an outlet or a fixture. Stop here and call an electrician. Resetting a breaker into a short over and over is how wiring gets damaged.
How to reset a tripped breaker
A tripped breaker doesn't go all the way to OFF. The handle stops in the middle, which can make it hard to spot. The simulator makes you do it the real way:
Find it. Open the panel door (not the inner cover). Look for the handle that's out of line with the others, sometimes with a red or orange window showing.
Push it firmly to OFF. You'll feel a click as the latch resets. Pushing straight to ON from the middle does nothing.
Push it to ON. If it won't stay, it either has a fault on it or (after an overload) needs a minute to cool.
Can I replace a 15 amp breaker with a 20 amp breaker?
No. It's the most common and most dangerous "fix". The breaker's size is set by the wire, not by what you want to plug in:
Copper wire
Largest breaker allowed
14 AWG
15 A
12 AWG
20 A
10 AWG
30 A
Those limits come from NEC 240.4(D). Put a 20 amp breaker on 14-gauge wire and the breaker happily lets 19 amps through a wire built for 15. Nothing trips; the wire just cooks inside the wall. In the simulator, the 15 A and 20 A buttons always switch the wire gauge too, because they belong together. If you need more power somewhere, the answer is a new circuit, not a bigger breaker.
GFCI and AFCI breakers: protecting people and stopping arcs
Try the ground fault tab: drag the hair dryer into the sink with a standard breaker installed. About 80 thousandths of an amp leaks through the water, and the breaker doesn't notice: it only sees 12.6 amps, well under 15. A leak that small can still stop a heart. Switch the breaker (top left of the panel) to GFCI and it trips in about 1/40 of a second, because it measures the difference between hot and neutral instead of the total. A Class A GFCI must trip by 6 milliamps.
That's why codes require GFCI protection near water: bathrooms, kitchens, garages, outdoors, basements and laundry areas (the exact list depends on which code edition your area uses). It can be a GFCI breaker in the panel or a GFCI outlet with Test/Reset buttons, which also protects the outlets downstream of it.
AFCI (arc-fault) breakers look for the electrical "signature" of a spark: a frayed cord, a nail through a cable, a loose connection. Those arcs often draw too little current for a regular breaker to notice, yet they start fires. Newer homes have AFCI protection on most living-area circuits. An AFCI that trips on its own is worth taking seriously: unplug things one at a time, as above.
When to call an electrician
The breaker trips with nothing plugged in.
You smell burning plastic, or see scorch marks on an outlet, switch or the panel.
An outlet, switch plate or the breaker itself feels warm.
Lights dim or flicker when something turns on, or outlets work intermittently.
A breaker won't reset, feels loose, or trips more and more easily.
You have an older panel brand such as Federal Pacific (Stab-Lok) or Zinsco, which have a reputation for breakers that fail to trip.
You need more capacity: an electrician can add a dedicated circuit for a heater, a freezer or a workshop.
Video walkthrough
Prefer to watch? This 3½-minute video runs the same simulator: an overload that trips slowly, a short circuit in slow motion, a ground fault with and without a GFCI, the time-current curve, and why a bigger breaker isn't the fix. It's also on YouTube.
FAQ
Why does my breaker trip when I use a space heater or hair dryer?
Each of them draws about 12.5 amps on its own. Add anything else on the same circuit and you pass 15 amps, so a 15 amp breaker heats up and trips after a minute or two. Move one of them to an outlet on a different circuit.
Why does my breaker trip immediately when I reset it?
An instant trip points to a short circuit or a ground fault, not an overload. Unplug everything on the circuit and reset. If it holds, plug things back in one at a time to find the culprit. If it still trips with nothing plugged in, the problem is in the wiring: stop and call an electrician.
Can I replace a 15 amp breaker with a 20 amp breaker?
Not unless the whole circuit is wired with 12 AWG copper or larger. The breaker is sized to protect the wire: 14 AWG copper is limited to 15 amps. A bigger breaker on that wire lets it overheat inside the wall without tripping.
Can a circuit breaker go bad?
Yes. Breakers can wear out, especially after many trips, and then trip too easily or feel loose and hot. But it is usually the last thing to suspect. Rule out overloads and faulty appliances first, and have an electrician test and replace a breaker.
Is it dangerous if a breaker keeps tripping?
The trip itself is the breaker doing its job. It is a warning that something on the circuit draws too much current or has a fault. Find the cause instead of resetting it over and over, and call an electrician if you smell burning, see scorch marks, or it trips with nothing plugged in.
Can I plug a space heater into a power strip?
No. A power strip adds outlets, not capacity, and most are not rated for a heater's continuous 12.5 amp draw. Plug space heaters directly into a wall outlet, ideally one with nothing else running on that circuit.
Why does my breaker trip when nothing is on?
Usually something is still running: a refrigerator or freezer compressor, a furnace blower or a dehumidifier can start on its own and push a nearly full circuit over. If it trips with everything truly unplugged, look for moisture in an outdoor or basement outlet, or an AFCI or GFCI reacting to a wiring fault, and have an electrician check it.
Why does my breaker trip when it rains?
Water is getting into an outdoor outlet, a light fixture or a buried cable and leaking current to ground, and a GFCI trips on that leak. Use weatherproof in-use covers on outdoor outlets and have damaged outdoor wiring repaired.
What's the difference between a 15 amp and a 20 amp outlet?
A 20 amp outlet has a sideways "T" on one slot so it can accept 20 amp plugs. Both kinds can be installed on a 20 amp circuit; only 15 amp outlets go on a 15 amp circuit. The outlet doesn't change how much current the circuit can carry. The breaker and wire do.
Still stuck? Ask me
A breaker that trips in a way this page doesn't explain, or a different topic you'd like taken apart like this? Ask here. Popular questions become new simulators.
This guide models one US 120 V branch circuit with a standard thermal-magnetic breaker. The trip times in the simulator come from a simplified thermal model and are illustrative; real breakers trip inside a band published by each manufacturer. It isn't a substitute for your local electrical code, permits, or a licensed electrician. Code references: NEC 240.4(D) (conductor protection), 210.23 (80% limit for plug-in equipment), 210.8 (GFCI), 210.12 (AFCI); UL 489 (breakers) and UL 943 (GFCIs).
