It's three in the afternoon, the heat index is 112, and the air conditioner has been running since ten that morning. Then the breaker trips. You reset it, the house cools for twenty minutes, and it trips again.
Nine times out of ten that isn't an air conditioner problem. It's an electrical one, and it's usually the same three things. The compressor is asking for more current than the circuit wants to give. The breaker is already hot before the compressor even starts. And the panel was never sized with a Louisiana summer in mind.
Locked rotor amps, in plain numbers
An AC compressor is a sealed induction motor, and induction motors have one bad habit. They don't make back pressure until they're already spinning, so for the first split second they pull whatever the utility will push through them. That surge is what the trade calls locked rotor amps (LRA). On most residential condensers it runs five to seven times the running amps printed on the nameplate.
A four-ton condenser in a Baton Rouge backyard usually carries a running load of about 20 amps and an LRA up around 105 to 110. The running number is what the wire and the breaker are chosen for. The LRA is what the compressor briefly asks for, and the gap between those two numbers is where every nuisance trip starts.
In mild weather that surge is over before it matters. In an August heat soak it isn't.
Why a hot afternoon changes the math
A condenser sitting in the sun at 100 degrees doesn't hold the same refrigerant pressures as one running on a 75 degree morning. The head pressure on the high side climbs, so the compressor has to push against it to get moving. Higher resistance means a longer start, and a longer start means more heat, which is how the whole event outlasts what the breaker wants to tolerate.
Then there's the breaker itself. A standard residential breaker is thermal-magnetic. The magnetic half clears a dead short instantly. The thermal half is a bimetallic strip that bends as current heats it, and its trip curve is calibrated to a fixed ambient temperature. Under UL 489 a manufacturer can pick either 77 or 104 degrees Fahrenheit as that calibration point, and either way the number describes the air around the panel rather than the air in your house.
A lot of panels around here aren't sitting in normal room air. They're on a west-facing exterior wall or in a garage that has been baking all afternoon, and the inside of that enclosure can run well past 104 before anything in the house turns on. The strip is already partway bent when the compressor hits it with LRA. It doesn't take much on top of that to finish the job.
That's also why the trip tends to happen on a restart. If the thermostat calls for cooling again before the refrigerant pressures have equalized, the compressor starts against a head of pressure it wouldn't normally face, and the start takes longer.
The flicker is the tell
If your lights dip every time the condenser kicks on, you're watching the startup current drag the voltage down across the whole panel. That's worth fixing for its own sake. Every dim is a small voltage sag reaching your fridge, your router and anything else with a control board in it.
Hard start kit or soft starter
Both get called "hard start kits" by homeowners, and they aren't the same part.
A hard start kit is a start capacitor with a potential relay, wired at the condenser. The capacitor gives the start winding a shove, and the relay takes it back out of the circuit once the motor is up to roughly 75 or 80 percent of full speed. It raises starting torque, which is exactly what an older compressor fighting high head pressure needs. It's the cheapest real fix on the truck, which is why the trade reaches for it first.
A soft starter sits in the same place and works differently. It's solid state, and it ramps the voltage up over the first fraction of a second instead of letting the motor take the full hit at once. That cuts the inrush substantially, which is why soft starters are what people reach for when a generator has to carry a 3 to 5 ton unit, or when the lights have been dimming for years.
Which one you need depends on the compressor, the age of the unit and what the circuit is doing under load. Guessing is how people end up with the wrong part bolted to a condenser.
The circuit has to match the nameplate
HVAC equipment is its own article in the code, Article 440, and it doesn't follow the same sizing logic as the rest of the house. Two numbers on the nameplate rule the install. Minimum circuit ampacity is the smallest conductor the unit is allowed to run on. Maximum overcurrent protection is the largest breaker or fuse the manufacturer permits ahead of it. The wire is sized to the first number and the breaker to the second, and they're often not the number you'd have guessed.
That matters when a compressor is replaced, because the new unit is rarely the same size as the old one. Putting a larger compressor on a circuit that was run for a smaller one gives you voltage drop on the conductor, and a motor running on low voltage pulls more current to make the same horsepower. It runs hot and shortens its own life, and it trips the breaker on the hottest day of the year. In the newer subdivisions out toward Prairieville the houses are bigger and so are the systems, which is where a four or five ton condenser ends up on a circuit that was sized for the three ton unit it replaced.
One thing never to try: a bigger breaker on the same wire. That doesn't fix a trip. It removes the protection that was keeping the conductor inside your walls from acting as a heating element.
Questions I get asked
Why does it trip right after it just ran?
Because the system didn't have time to equalize. The compressor is starting against residual head pressure, which means that start draws out longer than it would from a cold start.
Can I just put in a bigger breaker?
No, and this is the one I won't do. Upsizing the breaker without upsizing the conductor is how a nuisance trip turns into a fire.
What's the difference between the breaker in my panel and the box outside?
The panel breaker protects the wire between the panel and the condenser. The disconnect at the unit gives a technician a way to kill power at the equipment. Some of them carry a fuse and some are just a switch.
What if the problem is out at the pole?
Then it belongs to Entergy Louisiana, and you want them out to look at it. Your side starts at the weatherhead and the meter can and runs back into the house. If the voltage sagging into your service is coming off the line side, that's a utility call rather than an electrician call, and I'd rather tell you that than sell you work you don't need.
What to do about it
If your AC is tripping breakers on hot afternoons, the useful step is a load evaluation rather than another reset. We come out, measure what the compressor actually pulls on start, look at the conductor size against the nameplate, check the breaker for heat damage from all that cycling, and tell you whether this is a starting component, a circuit problem or a panel that has been running hot for years.
That's the difference between a fix and another summer of resets.