Quick answer
The 7 reasons a breaker trips — at a glance
- Overloaded circuit — too many things on one circuit (most common)
- Short circuit — hot wire touches neutral, trips instantly
- Ground fault — hot wire contacts ground, shock risk near water
- Worn-out breaker — the breaker itself is tired
- Wrong breaker size — mismatched wire gauge after DIY work
- Panel at capacity — 100A panel struggling with modern loads
- Zinsco or Federal Pacific panel — replace immediately
Scroll down for the full diagnosis guide on each one, or use the table of contents on the left.
Overloaded circuit — the most common reason
- Happens when too many devices share the same circuit
- Breaker trips after several minutes of heavy use — not instantly
- Typical spots: kitchen, garage, basement workshop
This is the number one reason breakers trip in Montreal homes, especially in houses built before 1995 when the wiring was sized for far fewer appliances.
A 15A circuit is designed to handle 1,440W continuously (80% of 1,800W rated). One microwave, one toaster, and a kettle on the same circuit will push well past that. The breaker heats up and trips.
The tell-tale sign is that the breaker trips after a few minutes of combined use — not the instant you plug something in. If it trips right away, scroll down to cause #2.
What to do right now: Unplug everything on that circuit, reset the breaker, then add devices back one at a time. When it trips again, that's your culprit. Long-term fix: add a dedicated circuit for the heavy appliance, or split the circuit.
Short circuit — trips instantly, sometimes with a bang
- Hot wire contacts neutral wire directly — resistance drops to near zero
- Breaker trips the instant the circuit is engaged
- Sometimes accompanied by a pop, flash, or burning smell
A short circuit is a different category of problem from overloading. Instead of too much current flowing through a normal path, current is taking a shortcut it shouldn't. This causes an immediate current spike that trips the breaker almost instantaneously.
Common causes: a damaged extension cord (the insulation has worn through), a faulty appliance with an internal wiring failure, or physical damage to wires inside a wall — from a nail, screw, or pest chewing through insulation.
If you plug in an appliance and the breaker trips in under a second, test that appliance on a completely different circuit. If the problem follows the appliance, the appliance is faulty. If the breaker trips with nothing plugged in, the short is in the wiring.
Do not keep resetting a breaker that trips instantly. A persistent short that isn't repaired can start a fire inside the wall. This is a call-an-electrician situation.
Ground fault — the shock hazard hiding near water
- Hot wire touches a ground wire or grounded surface (metal pipe, wet drywall)
- Most common in bathrooms, kitchens, laundry rooms, outdoors
- GFCI outlets are specifically designed to catch this before the breaker does
A ground fault is the shock-risk cousin of a short circuit. Instead of hot touching neutral, the hot wire contacts the ground — either directly, or through a conductive surface that happens to be grounded (think: metal pipe, damp concrete, a wet outlet box).
In wet areas, moisture can bridge the gap between a hot wire and a ground surface. That's why electrical code requires GFCI-protected outlets near every water source. If a GFCI outlet is tripping rather than your breaker, the system is working exactly as designed — a ground fault is being caught before it can shock you.
If your GFCI keeps tripping: check the outlets downstream on the same circuit first. A damaged cord plugged into a bathroom outlet two rooms away can cause the hallway GFCI to trip. Unplug everything downstream, reset, and re-plug devices one at a time.
What NOT to do: Replace a tripping GFCI with a regular outlet to 'fix' the tripping. That disables the only protection between a ground fault and a person getting electrocuted.
Worn-out breaker — it's not always the circuit
- Breakers are mechanical — they wear out over 15–25 years
- A tired breaker trips at loads it used to handle without complaining
- Breaker replacement is usually quick and affordable
People assume the circuit is the problem. Sometimes the breaker itself is just old.
Breakers have a spring-loaded tripping mechanism. After 15–25 years of normal operation — and especially after repeated trips and resets — that mechanism gets weaker. It starts tripping at currents it was originally rated to handle comfortably.
If you genuinely haven't changed anything on a circuit (no new appliances, no renovation) and a breaker that was fine last year is suddenly tripping regularly, suspect the breaker itself.
A worn breaker can also feel different from its neighbours when you flip it — stiffer, looser, or it doesn't fully click back into the ON position. That's a sign the mechanism is compromised.
What to do: Breaker replacement is usually a 45-minute job. A standard 15A or 20A breaker runs $20–$60 in parts. Get a diagnosis first — don't just replace breakers blindly — but if the circuit tests clean and everything else checks out, the breaker is the likely culprit.
Wrong breaker size — a DIY wiring mistake
- 14-gauge wire is rated for 15A. 12-gauge for 20A. They must match.
- A 20A breaker on 14-gauge wire means the wire overheats before the breaker trips
- Common after DIY work, permit-less renovations, or 'temporary' fixes
This is less common than the others but more dangerous when it occurs. The breaker is the wire's protection. It trips before the wire can overheat and start a fire. This safety function only works if the breaker is correctly sized for the wire gauge.
14-gauge copper wire is rated for 15A maximum. 12-gauge is rated for 20A. If someone installed a 20A breaker on a 14-gauge circuit — often to 'stop a breaker from tripping' — the wire can now carry 20A before the breaker trips. At that current level, 14-gauge wire heats up significantly. Inside a wall, that means fire risk.
The reverse is also possible: a 15A breaker on a circuit that consistently runs 16–18A will trip constantly. The load sizing was wrong, not the protection.
What to do: This requires opening the panel to verify wire gauge vs. breaker rating. If your home has had any DIY electrical work, permit-less additions, or flips, this is worth having an electrician verify. It's not a 'get to it someday' issue — it's a fire hazard.
Panel at capacity — the modern appliance problem
- Montreal has thousands of homes with 100A service, sized for 1970s loads
- EV chargers, heat pumps, and electric dryers push old panels to the limit
- Panel upgrade to 200A is the practical long-term fix
A 100A electrical panel was a reasonable size for a 1970s home with gas appliances, a few lights, and a television. Today's typical Montreal home runs electric baseboard heat, a heat pump, a Level 2 EV charger, an electric dryer, a home office, and multiple large screens simultaneously.
When a 100A panel is consistently running near its rated limit, the main breaker gets stressed. You start seeing seemingly random trips across multiple circuits — not because any single circuit is overloaded, but because the whole panel is being pushed.
Signs that panel capacity is the issue: multiple breakers trip at the same time, the main breaker trips (the big one at the top), or tripping correlates with cold weather when baseboard heaters run constantly.
What to do: An electrician can do a load calculation in under an hour to assess your actual average draw. If you're regularly exceeding 80A, a 200A upgrade makes sense. In Montreal, this means coordinating with Hydro-Québec for the service entrance — typically a half-day project. Budget $2,000–$4,000 all-in.
Zinsco or Federal Pacific panel — not a normal breaker problem
- Zinsco (including Sylvania) and Federal Pacific Electric (Stab-Lok) panels have documented failure rates
- Breakers can fail to trip under overload — the protection doesn't work reliably
- Common in Montreal homes built 1960s–early 1980s
If you have one of these panels, the tripping breaker is the least of your concerns.
Both Zinsco and Federal Pacific Electric (FPE) panels have well-documented histories of breaker mechanisms that fail to trip under overload or short-circuit conditions. Meaning the protection the breaker is supposed to provide doesn't reliably work. This failure mode has been associated with residential fires in Canada and the US.
These aren't just aging panels — the design of the bus/breaker interface is fundamentally flawed. You can't fix it by replacing individual breakers; the entire panel needs to go.
How to know if you have one: Look at the brand name on the panel door. Zinsco panels often have coloured breaker handles (orange, blue, green). FPE Stab-Lok panels often have red breakers and the words 'Stab-Lok' on the breakers themselves. Homes in Montreal built between 1960 and 1985 are most likely to have them.
What to do: Schedule a panel replacement. This isn't an 'eventually' item. The tripping is just the panel showing its symptoms — the actual risk is that it may stop tripping when it should.
All 7 causes at a glance — comparison table
| Cause | When it trips | Key signs | DIY? | Urgency |
|---|---|---|---|---|
| Overloaded circuit | After a few minutes | Multiple devices running | Yes | Medium |
| Short circuit | Instantly | Pop / burning smell | Partial | High |
| Ground fault | Instantly (GFCI) | Near water sources | Partial | High |
| Worn-out breaker | Randomly | Old panel, no new load | No | Medium |
| Wrong breaker size | Regularly at load | Post-DIY work | No | High |
| Panel at capacity | Multiple circuits | Added EV/heat pump | No | Medium |
| Zinsco / FPE | Unpredictably | Pre-1985 home | No | Critical |
When do you actually need to call an electrician?
Some tripping breakers you can fix in 10 minutes by unplugging devices and reorganising your loads. Others put you at real risk if you keep resetting them. Here is the honest breakdown:
You can probably handle it yourself if:
- The breaker trips after running several things at once — redistribute the load across different circuits
- A single troublesome appliance is causing it — test the appliance on another circuit, replace if faulty
- Your GFCI outlet is tripping and you can identify which downstream outlet is the cause
Call a licensed electrician if:
- The breaker trips the instant you reset it — even with nothing plugged in
- You smell burning, hear a pop, or see any darkening/scorch marks near outlets or the panel
- Multiple circuits are tripping without obvious cause
- You have a Zinsco or Federal Pacific Electric (Stab-Lok) panel
- The main breaker is tripping (the large breaker at the top of the panel)
- Any of this started right after DIY electrical work
Not sure which category you're in?
Describe what your breaker is doing — when it trips, what was running, how old the panel is — and we'll tell you whether it's a simple fix or something that needs attention. No charge for the phone diagnosis.
Frequently asked questions
Electrique 360
Licensed electrical contractors in Greater Montreal. RBQ Licence 5839-5724-01. We publish these guides to give homeowners a straight answer before they pick up the phone — so when you do call, you already know what you're dealing with.