Breaker Trips When AC Turns On — Why and How to Fix It
An air conditioner that trips the breaker every time it starts — or after running for a while — is one of the most common summer electrical complaints. The problem can range from a simple overloaded circuit to a failing compressor. Here is how to diagnose it.
Why AC Units Are Hard on Breakers
Air conditioners draw significantly more current when starting than when running. A 240V central AC unit rated at 20 amps running may draw 40–60 amps for the first few seconds during startup (called inrush current). This startup surge is normal — but if the breaker is already weakened or the circuit is undersized, it can trip.
Cause 1: Dirty Air Filter or Blocked Condenser
A dirty air filter or blocked condenser coil forces the AC compressor to work harder, drawing more current than normal. This is the most common and easiest-to-fix cause of AC breaker trips.
Fix: replace the air filter and clean the condenser coils. Run the AC again and see if the tripping stops.
Cause 2: Overloaded Circuit
If the AC is on a circuit with other loads, the combined draw may exceed the breaker's rating. Central AC units should always be on a dedicated circuit.
Fix: ensure the AC is on a dedicated circuit sized for its nameplate amperage plus a 25% safety margin.
Cause 3: Weakened or Undersized Breaker
A breaker that has tripped many times, or one that was originally undersized for the AC unit, may trip on the startup surge even when the AC is working normally.
Fix: have an electrician verify the breaker size matches the AC nameplate requirements. Replace the breaker if it is faulty.
Cause 4: Failing AC Compressor
A compressor that is beginning to fail draws much higher current than normal — sometimes 3–4x its rated amperage. This will trip even a correctly sized, healthy breaker.
Signs: the AC runs for a while then trips, or the breaker trips immediately when the compressor tries to start. The breaker may be hot after tripping.
Fix: have an HVAC technician test the compressor. A failing compressor usually needs replacement.
Cause 5: Low Refrigerant
Low refrigerant causes the compressor to work harder and run longer, drawing more current over time. This can cause the breaker to trip after the AC has been running for 10–30 minutes.
Fix: have an HVAC technician check and recharge the refrigerant.
Related Circuit Breaker Resources
- Why Does My Circuit Breaker Keep Tripping?
- What Size Circuit Breaker Do I Need?
- How Long Do Circuit Breakers Last?
Need a replacement breaker for your AC circuit? Call AllBreakerSales.com at (951) 903-9804 — our catalog includes 2-pole breakers in all amperages. Current availability is confirmed in the written quote.