Furnace Keeps Tripping the Breaker? Causes and What to Check
Furnace tripping the breaker? A dirty filter, a failing blower motor or a shorted igniter are common causes. Check the timing, the filter and when to call.
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A furnace breaker usually trips for one of two reasons: a short in the igniter, inducer motor, blower or heat strip, which trips it as soon as heat starts, or restricted airflow that overworks the blower and trips it after the furnace has run a while. Replace a dirty filter, open blocked vents and, if it keeps tripping, call a licensed technician.
Timing is your best clue. Note when the trip happens before you start checking.
What the timing tells you
| When it trips | Likely cause |
|---|---|
| Right when heat starts | Short in igniter, inducer motor or heat strip |
| When the blower starts | Failed capacitor or seized or shorted blower motor |
| After running a while | Restricted airflow, overheating |
| Randomly | Worn breaker or loose wiring |
Common causes
- Dirty filter and blocked vents. The most frequent airflow problem. The blower works harder and draws more current.
- Failing blower motor. A seized or shorted motor draws a lot of current. One source notes a motor can spin freely by hand and still trip the breaker if its windings are damaged.
- Bad run capacitor. It stops the motor starting properly and causes high inrush current.
- Cracked igniter. Hot surface igniters can crack and short.
- Wet inducer motor. Water getting into it can short the motor.
- Electric heat strip. A short in the strip trips the breaker when heat is called.
How to fix it
- Turn the thermostat off and switch the furnace off at its switch.
- Replace the air filter if it is dirty.
- Open all supply registers and clear the return vents of furniture and rugs.
- Reset the breaker once and turn the furnace on.
- Note when it trips. If it trips right away, stop and call a technician.
If you notice an odd smell when heat starts, see what causes a burning smell from the heat.
When to call a professional
- It trips as soon as heat starts or the blower runs.
- A new filter and clear vents make no difference.
- You see scorch marks or smell burning.
- The breaker will not reset.
If the house is cold in the meantime, see a plan for heating during an outage for staying warm safely, and why hot water fails in winter if the water heater is acting up too.
What not to do
- Do not install a bigger breaker.
- Do not keep resetting the breaker.
- Do not open electrical panels on the furnace with the power on.
- Do not run the furnace with a blocked filter.
Bottom line
Check the filter and vents first. If the furnace still trips, or trips at once, a motor, igniter or heat strip has a fault that needs a technician.
Sources
This guide was checked against these official and manufacturer sources.
Frequently asked questions
Why does my furnace keep tripping the breaker?
If it trips the moment heat starts, suspect a short in the igniter, the inducer motor or an electric heat strip. If it trips after running a while, the cause is often restricted airflow, such as a dirty filter, making the blower work harder.
Can a dirty filter trip the breaker?
Yes. A clogged filter or blocked vents make the blower motor draw extra current, which can trip the breaker after the furnace has run for a while.
Is it safe to keep resetting the breaker?
No. If the breaker trips immediately, there may be a short, which is a fire risk. Switch the furnace off and call a technician.
Can I use a larger breaker?
No. Oversizing a breaker is dangerous and breaks electrical code.
Written by
Agha Ali Abbas
Agha Ali Abbas is the founder and editor of TimeToNote. He has worked in SEO and content writing for 18 years, and he checks every guide against manufacturer documentation and official sources before it goes live.
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