Furnace Tripping Breaker? Reset Once, Then Call
Why it trips, the one reset that is reasonable, and who should fix what.
The short answer: A furnace tripping breaker means the furnace circuit drew more current than it safely should or developed a fault, usually from a worn blower motor or capacitor, damaged wiring, an igniter fault or a shared circuit. Set the thermostat to Off, unplug anything else on that circuit, then reset the breaker once. If it trips again, leave it off and call a technician.
The furnace has gone quiet, and in the basement one breaker sits between On and Off. A furnace tripping breaker is your electrical system doing its job: it cut the power because something on that circuit pulled too much current or let electricity go where it should not. The real questions are why, and whether it is safe to turn it back on.
This guide for Ontario and GTA homeowners covers the one reset that utilities consider reasonable, what the timing of a trip reveals, the seven common causes and which trade fixes each. Nothing here asks you to open the furnace, touch wiring or use a meter. If the heat is already off, book a repair visit online or call 310-HEAT any time.
The one-reset rule
Only if nothing looks, smells or sounds wrong at the panel.
Skip the reset if you smell burning, see scorch marks, hear crackling or find water near the panel. See stop signs below.
What a Furnace Tripping Breaker Is Telling You
A breaker is a safety switch. When current climbs past its rating, or electricity finds a path it should not, the breaker opens and cuts power before the wires overheat. A gas furnace needs that electricity for its controls, igniter, inducer fan and blower, so a trip means no heat even with gas available.
The Electrical Safety Authority (ESA) homeowner handbook says circuits that frequently trip indicate overloading or possibly faulty wiring, and advises contacting a Licensed Electrical Contractor as soon as possible. One trip on a bitter night can be a one-off. A furnace tripping breakers again and again is a pattern that needs a diagnosis.
Rule out look-alikes. A blank wall display is often a thermostat not working, and a flashing status light is covered in our furnace blinking light guide. A dark status light suggests no power at all.
Furnace Tripping Breaker? The Timing Is Your Best Clue
Note when your furnace tripping breaker event happens and what else was running, then tell your technician.
| When it trips | What it often points to | Who usually fixes it |
|---|---|---|
| The moment you reset it | A short in the wiring or in a component | HVAC technician or electrician |
| When the blower fan starts | A failing blower motor or run capacitor | HVAC technician |
| At the start of a cycle, before the flame | An igniter or inducer motor fault | HVAC technician |
| After a long run time | An overheating motor or a weak breaker | HVAC technician first |
| Only when another appliance is on | A shared, overloaded circuit | Licensed electrician |
| After water appears near the furnace | Moisture reaching electrical parts | HVAC technician |
These are patterns, not a diagnosis; only a technician can confirm the cause.
7 Common Causes of a Furnace Tripping Breaker
Most furnace tripping breaker calls trace back to one of these seven.
1. Worn blower motor or weak capacitor
The blower is the biggest electrical load in a gas furnace. Worn bearings, a dirty wheel or a weak run capacitor make the motor draw extra current, often at start-up. A hum or squeal often comes first; see our guide to a furnace making noise.
HVAC technician2. Shorted or damaged wiring
Vibration, heat, age and rodents can wear through wire insulation inside the furnace or along its circuit. A bare conductor touching metal causes an instant trip.
Either trade3. Igniter or inducer motor fault
Both power up at the start of each heat cycle. A shorted igniter or a seizing inducer motor can overload the circuit just as the furnace tries to light. See what causes a bad furnace ignitor for the igniter side.
HVAC technician4. Overloaded or shared circuit
Ideally, a furnace has a circuit of its own. In some older homes and finished basements it shares one with outlets or lights, and a dehumidifier or hair dryer can push the total past the limit.
Licensed electrician5. Space heaters on the same circuit
A portable heater draws a lot of power on its own. If it shares a circuit with the furnace, the two can trip the breaker when the blower starts. Our space heater vs furnace comparison explains when one makes sense.
Homeowner habit6. Worn or weak breaker
Breakers are mechanical and can weaken with age and repeated trips, tripping below their rated load. Replacement is a job for a Licensed Electrical Contractor, never a do-it-yourself swap.
Licensed electrician7. Moisture and condensate leaks
High-efficiency furnaces produce water. A cracked drain, a blocked trap or a frozen condensate line can let water reach the control board or wiring. See why a gas furnace leaks water for the other causes.
HVAC technician
Safe Steps for a Furnace Tripping Breaker: Do and Do Not
One reset is ordinary utility advice. Toronto Hydro tells customers to flip a tripped breaker firmly to off and back on, and, if it trips again, not to reset it, since that may indicate a more serious problem for a qualified electrician.
Do
- Note when it tripped and what was running.
- Set the thermostat to Off first.
- Use a flashlight, with dry hands on a dry floor.
- Unplug space heaters sharing the circuit.
- Reset once, then leave it off if it trips again.
Do not
- Reset the breaker over and over.
- Remove the panel cover or any screws.
- Open the furnace, touch wiring or use a meter.
- Swap in a larger breaker or hold one on.
- Touch a panel that is wet, buzzing or smells of burning.
If your furnace has a light-style service switch nearby, note its position, leave it as is and mention it when you call.
Stop signs: leave the breaker off and get help now
- Smoke, sparks or flames: get everyone out and call 911.
- A burning plastic smell or scorch marks: leave it off and call. See our furnace burning smell guide.
- A rotten-egg smell: leave the home, then call Enbridge Gas at 1-866-763-5427 or 911 from outside.
- A carbon monoxide alarm: get everyone outside and call 911.
HVAC Technician or Licensed Electrician?
A furnace tripping breaker can be an equipment fault or a circuit fault, and those belong to two trades.
Your HVAC technician
- Blower motor and run capacitor
- Igniter and inducer motor
- Wiring and controls inside the furnace
- Condensate drains and humidifier leaks
A Licensed Electrical Contractor
- The panel and its breakers
- Wiring from the panel to the furnace
- Adding a dedicated furnace circuit
- Outlets and wiring in walls
In Ontario, anyone you hire for electrical work must be licensed; ESA suggests asking for the contractor's ECRA/ESA licence number, and its online locator finds one near you. Often the best first call is to the furnace side: our HVAC servicing and repairs team can tell you whether the fault is in the equipment or the circuit.
Staying Warm Safely While You Wait
While a furnace tripping breaker keeps the heat off, the house cools as it would in a blackout; our furnace during a power outage guide covers longer waits. For now:
- Use a certified heater with a CSA, cUL or cETL mark, as Health Canada advises.
- Plug it straight into the wall, on a different circuit. Health Canada warns never to use an extension cord or power bar.
- Give it space: at least 1 metre from curtains and bedding, unplugged before sleep.
- Never heat with fuel indoors. A barbecue, camp stove or generator can produce deadly carbon monoxide.
Preventing the Next Trip
- Book a yearly tune-up. A technician can catch many furnace tripping breaker faults early by checking motor current, the capacitor, the igniter, wiring and the drain. Our maintenance and protection plans include it.
- Keep space heaters off the furnace circuit and label which breaker feeds the furnace.
- Watch for water around the furnace and book a furnace repair at the first drip.
- Plan bigger loads. A heat pump or EV charger changes electrical demand; see our 100 amp panel and heat pump guide.
Local Help When the Breaker Will Not Stay On
Aire One has kept York Region and GTA homes warm since 1990, with TSSA-registered, NATE-certified technicians on call 24/7 and a 4.8-star Google rating from 541 reviews. We serve Markham, Richmond Hill and nearby communities, and a service call is $79. If a repeat furnace tripping breaker problem points to an aging furnace, ask about our free Total Home Assessment, financing and 10-year worry-free warranty. Learn more about our HVAC company in Markham and our HVAC company in Richmond Hill.
Breaker tripped a second time?
Leave it off. Our technicians answer 24/7.
310-HEAT (310-4328) · 24/7 service · $79 service call*
Frequently Asked Questions
Is it safe to reset a furnace breaker?
Once, in most cases. Set the thermostat to Off, unplug anything else on that circuit, then switch the breaker firmly to Off and back to On. Toronto Hydro advises against resetting a breaker that trips again, and you should skip the reset if you smell burning.
Why does my furnace trip the breaker when the blower starts?
The blower motor is the largest electrical load in a gas furnace, so a worn motor or weak run capacitor often trips the breaker at start-up. An HVAC technician should test both and replace them if needed.
Can a bad breaker cause a furnace tripping breaker problem?
Yes. Breakers wear out and can trip below their rating. Only a Licensed Electrical Contractor should test or replace one.
Can I use a space heater while the furnace is off?
Yes, with care. Use a certified heater plugged directly into a wall outlet on a different circuit, keep it at least 1 metre from anything that can burn, and unplug it before sleep.
Should I call an HVAC company or an electrician first?
If only the furnace circuit trips, start with an HVAC technician. If other circuits trip too, the panel buzzes or the furnace checks out, call a Licensed Electrical Contractor.
Sources and Helpful Resources
- Toronto Hydro: What to Do During an Outage (Tripped Breakers)
- Electrical Safety Authority: Homeowner Electrical Safety Handbook
- Electrical Safety Authority: Find a Licensed Electrical Contractor
- Health Canada: Electrical Product Safety
This article is general safety information for homeowners. When in doubt, leave the breaker off and call a professional.
Matthew leads the Aire One Markham and Metro Toronto team, helping homeowners keep their heating safe through every Ontario winter. Aire One has been a TSSA-registered, Carrier Factory Authorized Dealer since 1990.