Short answer
Start by confirming the breaker and circuit are correctly sized for the HVAC or appliance, then isolate whether the trip is caused by overload, a short/ground fault, or nuisance protection. Clean and inspect the equipment, check connections, and measure current draw with a clamp meter. If trips persist, especially instant trips or signs of overheating, call a licensed electrician or HVAC technician.
Why breakers trip with HVAC and major appliances
Major appliances and HVAC units use motors and heating elements that can cause high inrush current, sustained overload, or faults. Common causes include:
- Overload from dirty filters/coils causing motors to work harder
- Failing run/start capacitors leading to high amp draw or locked-rotor
- Loose or burnt connections at the breaker, disconnect, contactor, or lugs
- Short to ground in compressor, heating element, or wiring
- Mis-sized breaker or wire vs. equipment nameplate (MCA/MOP)
- Nuisance tripping on GFCI/AFCI where not required or due to shared neutrals
Example signs:
- Breaker trips instantly: likely short to ground or severe fault
- Trips after a few minutes: overheating motor, poor airflow, dirty coil, failing capacitor
- Trips only at start-up: high inrush, weak capacitor, locked-rotor, undersized circuit
What you need
- Non-contact voltage tester and a good flashlight
- True-RMS clamp meter (with inrush feature if possible)
- Multimeter with capacitance (for HVAC capacitors)
- Screwdrivers, nut drivers, and a torque screwdriver for lugs
- Infrared thermometer (optional) for hot spots
- Replacement air filter, coil cleaner, soft brush
- PPE: safety glasses, insulated gloves
Quick safety notes
- Turn off power at the breaker and verify with a tester before opening any panels. Avoid live work in the main panel.
- Capacitors can hold charge; discharge properly before testing or replacing.
- Refrigerant and sealed-system repairs require certification.
- If you smell burning, see melted insulation, or the breaker trips immediately after reset, stop and call a pro.
Step-by-step troubleshooting
1) Identify the exact circuit and load
- Label which breaker is tripping and what it feeds. Many HVAC systems have two circuits: outdoor condenser and indoor air handler/furnace.
- For appliances, confirm if they are on a dedicated circuit (dryer, range, water heater should be).
2) Check nameplate vs. breaker and wire
Read the equipment nameplate:
MCA (Minimum Circuit Ampacity): e.g., 24 A
MOP (Maximum Overcurrent Protection): e.g., 40 A
Voltage: 208/230 V
- Breaker should not exceed MOP and wire gauge should support MCA.
- Examples:
- Electric dryer: typically 30 A, 240 V
- Range: 40–50 A, 240 V
- Water heater: 30 A, 240 V
- Outdoor condenser: often 20–60 A depending on unit
- If the breaker is undersized, a licensed electrician should correct it. Do not upsize without verifying wire gauge and nameplate.
3) Inspect and clean
- HVAC:
- Replace air filter.
- Clean condenser coil (outdoor unit) and evaporator coil if accessible. Straighten bent fins gently.
- Check that outdoor fan spins freely and there is no debris.
- Appliances:
- Dryer: clean lint trap and vent run; clogged vents cause high heat and higher current.
- Fridge: vacuum condenser coils.
Time: 30–90 minutes. Cost: $0–$30 in cleaners/filters.
4) Tighten and inspect electrical connections
- With power off, open the disconnect at the condenser or appliance junction box.
- Look for discoloration, melted insulation, or loose lugs.
- Retorque lugs to manufacturer specs using a torque screwdriver. Re-terminate any burnt conductors.
5) Measure running current
- Clip a clamp meter around the hot conductor and run the unit.
- Compare measured amps to nameplate RLA/FLA and MCA.
- If amps exceed normal by more than ~10–20%, look for airflow issues, failing capacitors, or mechanical binding.
Tip: If trips occur only at startup, use the meter’s inrush function and compare to LRA. Persistent LRA-level current suggests a locked rotor or bad start components.
6) Test capacitors (HVAC)
- Power off and discharge the capacitor.
- Remove leads and measure capacitance; compare to rating (e.g., 40/5 µF). Replace if off by more than ±6–10%.
- Cost: $15–$60 for a run capacitor.
7) Check protection devices
- If the circuit uses GFCI/AFCI, verify it is required for that location/equipment. Some HVAC circuits are not GFCI-required and can nuisance-trip due to motor leakage. Do not remove required protection; consult code or an electrician.
- Inspect for shared neutral issues on multi-wire branch circuits feeding AFCI/GFCI devices.
8) Appliance-specific checks
- Dryer: check heating element for short to chassis with a multimeter (continuity from element to ground indicates a fault).
- Water heater: element short to ground will trip instantly; test each element with leads removed.
- Fridge/AC compressor: check winding to ground (infinite ohms expected). A reading to ground indicates a grounded compressor.
Best practices and tips
- Log the pattern: weather, time of day, start-up vs. run. This helps pinpoint inrush vs. thermal overload.
- Avoid extension cords for major appliances; they cause voltage drop and extra heat.
- Replace weak breakers only after confirming there is no underlying overload or fault. HACR-rated breakers are typical for HVAC.
- Consider a hard-start kit only after a tech confirms it is appropriate and the compressor is healthy.
Common mistakes
- Upsizing a breaker without matching wire size and nameplate MOP
- Ignoring loose neutrals/grounds or overheated lugs
- Neglecting airflow maintenance (dirty filters and coils)
- Swapping parts before measuring current and capacitance
- Installing tandem breakers in panels not listed for them
When to call a pro
- Immediate trips on reset, visible arcing, burned insulation, or hot buzzing breakers
- Aluminum branch wiring, subpanel feeder issues, or service upgrades
- Compressor grounded or locked rotor, repeated tripping after cleaning and capacitor replacement
- If you are not comfortable opening disconnects or testing live circuits
Typical costs:
- Electrician diagnostic: $150–300
- HVAC capacitor replacement: $100–250 (parts and labor)
- Breaker replacement: $15–60 part, plus labor
- Fan motor: $200–600
- Compressor or major sealed-system work: $1,200–3,000+
With careful inspection, proper measurements, and basic maintenance, many recurring trips can be resolved without guesswork. Prioritize safety, verify sizing against the nameplate, and do not hesitate to bring in a pro for persistent or hazardous faults.