How to Reset an AC Circuit Breaker, and What It Means If It Trips Again

In North America, one of the prime reasons for power problems in summer may be the AC breaker tripping, which may become troublesome when you reset it. The breaker has done what it should have, but the one needs to understand what makes it trip, as just waiting for five minutes does not guarantee the problem is fixed.

In order to avoid damaging the device, follow these instructions and learn about three ways to act.

In conclusion, switch OFF the breaker for a minimum of five minutes as the refrigerant pressure will be equalized in the compressor only after that. In the cases where the breaker turns ON and remains ON then it is suggested that there is only an overload issue that was temporary. In case the breaker trips there and then again, it signifies that a professional must be contacted as there might be a short-circuit in the system. If this occurs within a timeframe of ten to thirty minutes during the operation, the breaker may be weak and faulty capacitor or compressor draws a too high current.

Why an AC Breaker Trips in the First Place

An air conditioner is not a resistive load but is a compressor motor that has a locked rotor current of five to six times its running current, a condenser fan, and a control circuit. The inrush is normal, and the circuit breaker is sized for it. A trip indicates some condition has exceeded the design thresholds, and several common candidates may exist.

• A genuine overload. A dirty condenser coil, a failing fan motor, or a refrigerant charge problem pushes running current up until the thermal element in the breaker operates.
• Locked rotor. The compressor cannot start; it remains at locked-rotor current until either its internal protector or the breaker opens.
• A short circuit burns. Usually, it is a burnt wire at the contactor, a rubbed conductor against the cabinet, or a failed compressor winding.
• A ground fault provides moisture in the disconnect, a damaged whip, or a winding leaking to earth.
• A tired breaker. Years of repetitive heating and cooling through thermal cycling lead the breaker to trip at less than its rated setting, which makes the same unit break on the same circuit during the summer each time.

You’d only reset the first two without evaluating or diagnosing the cause. The other three will repeat quickly, and then repeating a fault into a compressor is how a $200 repair becomes a $2,000 replacement.How a thermal-magnetic device decides between a motor start and a fault is set out in our FAQ on breaker ratings and trip curves.

The Five-Minute Rule, and Why It Is Not Optional

Once a compressor halts, the high side remains under pressure while the low side does not. The motor then has to draw locked-rotor current due to the pressure difference. The pressures balance out through the metering device in around three to five minutes in most residential systems.

Resetting will not allow resolving the problem with the compressor; it only adds one more locked-rotor event to the motor. Do it a couple of times, and the compressor is going to start tripping because its internal overload is going to trip.

Patience is needed for at least five minutes. If there is a hard-start kit in the system or a scroll compressor with long equalization time, ten minutes wait is good engineering practice, and it prevents equipment damage.

Step by Step

• Switch the thermostat off to prevent the system from automatically activating while you carry out the repairs. Next, locate the circuit breaker, which should be a two-pole 240 V switch labeled “A/C”, “condenser” or “heat pump”. In case of a separate 120 V air handler part, ensure that the breaker is a single-pole one. Turn the breaker off completely to check if it is defective.
• Give it five minutes. Use the time for an observation of the outdoor unit, checking whether the disconnect is on, whether there is any ice formation on the pipes or whether the fan is rotated freely.
• When the five minutes expire, switch the breaker on, firmly. If the breaker won’t stay on after you touch it and it keeps tripping tripping, there may be a fault somewhere.
• Restore the thermostat settings at this moment. Watch carefully to see if the contactor is undergoing a single clack change and whether the fan starts followed by the compressor unit activation within a second or two. Any continuous clicking noise or grinding means that the system is unable to operate.

The single-pole branch device feeding a 120 V air handler is a conventional thermal-magnetic MCB, and its behaviour is described in the spec of this single-pole 32 to 63 A MCB, including the trip curve that decides whether a motor start is tolerated.

Reading the Outcome

There is one reason behind system not working electrically that needs to be mentioned: the condensate overflow switch. Most system have float switch in the drain pan that open the circuit if there is enough water in the pan. The thermostat shuts down, and the outdoor unit stops. The user rushes to the circuit breaker. In case the breaker is not tripped check the drain.

What the Condenser Circuit Should Look Like

In North America, a split-system condenser can be identified as a 240V load connected to a double-pole circuit breaker (with the current being at least at the minimum ampacity stated in the manufacturer’s rating document as well at the maximum value of the current). This means that those values are not the same and can hardly be guessed, as a 3-ton system could use either a 25A or a 30A breaker depending on the efficiency rates and features of the design.

The device in question is a thermal-magnetic double-pole breaker with C or D curves because the compressor starting is an inrush event that is considered a fault by the Curve B breakage. The construction and the pole arrangement are shown in this two-pole miniature circuit breaker, which is the same format used in the panel for 240 V residential circuits.

One should never try to ‘fix’ a tripping 30-amp breaker by installing a 40-amp breaker. The wire is rated to 30 amps. It is the breaker that protects the wire from overloading; if the breaker is oversize, the fault shifts from the panel to the walls.

When the Breaker Itself Is the Problem

A circuit breaker that trips at 20 amperes is not serving any purpose on a circuit carrying 18 amperes; it is just old. Thermal-magnetic circuit breakers deteriorate over time and one that has been subjected to excessive use will trip much sooner than its rating.

A number of predictors of the need to replace a circuit breaker can be evidenced: its body is warm on low loads, its lever is loose, its shell discoloured near terminals, and the fact that it trips at the same time every day regardless of the other conditions. All these are satisfactory reasons for replacing the unit, rather than resetting it a fourth time.

The procedure is a 20-minute job for the electrician, but it is a dangerous thing to do for an average homeowner as the busbars remain powered. Our technical service team will identify the correct series and rating from a photo of the panel label, which avoids the classic mistake of buying a breaker that fits the slot but not the bus.

Surge Protection on the AC Circuit

In many cases, repeated trips are often wrongly attributed to surges since surges only happen in microseconds and temperature breakers function in seconds. What actually happens is that a surge causes damage to the contactor coil, control board, and capacitor, all of which then result in a trip which is blamed on the surge.

Therefore, a Type 2 surge protection device installed in the main panel is the solution as it protects electronic devices.The ratings that matter are the maximum discharge current and the voltage protection level; a Type 2 SPD rated 40 kA for distribution boards is the usual residential specification.

FAQ

How long to keep the breaker off to reset AC?

In general, you should turn the switch off at least five minutes. However, turning it off for ten minutes is even better.

Will resetting the breaker fix AC?

Resetting the breaker certainly has the potential to fix the issue most of the times—this is the case only if the system is faced with a temporary overload. In case the breaker fails again and again on the same day, it means that resetting did not require repair.

How do I reset my AC manually?

First, the thermostat must be turned off, then the breaker should be turned off too, and you have to wait a few minutes to turn the breaker back on and turn on the thermostat too.

How to tell if an AC breaker is blown?

It should be noted that unlike a fuse, which can be blown, a circuit breaker does not break. Instead, it trips and the handle turns between the on and off positions. In the case of a blown fuse, a new fuse should be installed. If the handle is in the on position and the system fails to work, it is usually because of some other problem in the disconnect, in the contactor, in the capacitor or even in the control panel.

References

• U.S. Department of Energy — Energy Saver: Heating and Cooling
• Energy Vanguard — HVAC Design and Commissioning Notes
• This Old House — Air Conditioning Repair Basics
• Bob Vila — Electrical Panel and Breaker Repairs
• NEMA — Air Conditioning and Refrigeration Equipment Standards

Conclusion

If you are pressing Reset, you need to wait for five minutes for the process to take place. After waiting for the time period, check the breaker for the current status.If your unit requires a two pole breaker of the said rating instead of a reset type breaker, please let us know about it so that we can arrange for the shipment of your device.