Central air conditioners demand a considerable amount of power. In fact, their energy demands regularly exceed the capabilities of the average home’s wiring. When an air conditioner enters its cooling cycle, it’s drawing from energy reserves that have been harnessed and stored by its capacitor. Although an AC capacitor doesn’t move refrigerant or cold air, it’s still a critical element of the cooling process. Without it, your air conditioner might turn on, but the temperature inside of your San Antonio home will remain unchanged. Understanding what an AC capacitor does and how its performance affects home comfort is key for recognizing developing issues and solving them.
The Role of the AC Capacitor in the Cooling Process
Despite being wired directly into your electrical system, your air conditioner doesn’t have enough power to initiate and complete a cooling cycle. The electricity provided by this connection is only sufficient for running your air conditioner in fan mode. If you want it to actually cool the building interior rather than simply circulating air, something will need to kick-start its motors. This is exactly what an AC capacitor does.
At the very start of the cooling cycle, the capacitor sends out powerful pulses of electricity to ramp the air conditioner’s motors up. Once the cooling cycle has been successfully started, the capacitor lowers its output and continues to provide a steady supply of power until the cooling cycle reaches its end. These actions seamlessly correspond with the thermostat setting and the real-time temperature indoors. Whenever the indoor temperature matches the temperature that’s been set at the thermostat, the AC capacitor pauses. However, it never actually remains completely dormant. In-between cooling cycles, this component harnesses the energy and stores it in preparation for the next cycle.
Single-Function vs. Dual-Function AC Capacitors
Most modern air conditioners have a single, dual-function capacitor. A dual-function capacitor provides micro-bursts of power to initiate the cooling cycle and then a lower but steady stream of power to keep the motor running until the desired indoor temperature is achieved.
Older air conditioners and several low-cost AC models actually have two separate, single-function capacitors instead. These are known as run capacitors and start capacitors. A start capacitor provides the initial jolt of energy that AC motors need to start up, and run capacitors keep air conditioner motors running throughout the cooling cycle. Air conditioners with dual-function capacitors tend to be smaller and more compact. A single, dual-function capacitor takes up far less space than two single-function units do.
If your air conditioner has two single-function AC capacitors, it might be possible to upgrade both of these to a dual-function unit. In many newer AC models with two capacitors, this upgrade can be performed at a very reasonable cost even when only one capacitor has failed. This way, if new capacitor problems ever arise in the future, only one unit will need to be repaired. This is an important investment to consider if your home is prone to power outages, short circuits, and nearby lightning strikes or if your AC condenser is an uncovered area and constantly subjected to direct sunlight.
Common Reasons Why AC Capacitors Break Down
AC capacitors have a tough job. When compared to many other AC components, capacitors have a fairly high likelihood of breaking down before an air conditioner has reached the end of its lifespan. Thus, if you have an air conditioner that’s rated to last 15 years or more, you’ll probably have to have its capacitor replaced at least once. In some households, AC capacitors might break down two or even three times throughout the course of an air conditioner’s lifespan. When this is the case, it’s largely the result of excess wear caused by frequent power surges.
One way to limit this type of AC capacitor wear is by having whole-house surge protection installed. A whole-house surge protector will protect all of your appliances and electrical devices from power outages and short circuits. Other common causes of AC capacitor problems include:
- Direct lightning strikes
- Impact events
- Exceedingly high temperatures that cause it to overheat
Having your AC condenser installed in a heavily shaded area can limit the likelihood of premature AC capacitor failure. You should also make sure that low-hanging branches and other foliage around the outdoor condensing unit are regularly limbed. This will prevent weak or dying tree branches from falling directly on top of your air conditioner’s outside component and causing major damage.
Signs Your AC Capacitor Has Failed
If your air conditioner doesn’t turn on, this may be a sign that its capacitor isn’t working. However, it is not uncommon for air conditioners to continue running even though their capacitors are broken. What an air conditioner cannot do without a functional capacitor is actually cool things down. Absent of the perfectly timed jolts of power that this unit provides, the cooling cycle will never be initiated. Thus, if your air conditioner has been running for quite some time and your living environment still feels hot and humid, a broken capacitor may be the culprit.
A broken or ill-performing capacitor can also cause:
- Rising energy bills
- Loud humming noises at the outside condenser unit
- Smoke and a faint, burnt odor at the outside condenser
- Delayed cooling cycles
When a capacitor is failing, air conditioners often shut themselves off at random.
Why Homeowners Should Never Try to Replace AC Capacitors on Their Own
Replacing an AC capacitor is a job for professionals. Although AC capacitors can and should be replaced when they fail or start performing erratically, it’s never safe to tackle this project on your own. These components are hardwired directly into the air conditioner’s condensing unit, and removing them and putting them back in poses the threat of electrocution. In terms of their functioning, AC capacitors are somewhat comparable to batteries. However, they aren’t simply pulled out and popped back in when things go awry. Not only is there the risk of serious and potentially fatal injuries, but there’s also the fact that tampering with these components can instantly void your manufacturer warranty.
It’s additionally important to note that identifying one or two signs of a failed capacitor is not enough to accurately diagnose this issue. HVAC professionals perform special tests to determine a capacitor’s:
These tests are the absolute best way to determine whether or not a capacitor is responsible for the problems that an air conditioner is experiencing and to ensure that replacing the capacitor will actually restore normal AC functioning.
At Beyer Air Conditioning & Heating, we’re proud to be a trusted provider of heating and cooling services to residents of the greater San Antonio, TX area. We also offer ductless AC systems, VRF systems, and indoor air quality services. Our team is NATE-certified, and our company is accredited by the BBB, Dave Lennox award winners, and are recognized as a Lennox #1 Training Company five years in a row. If your cooling system’s AC capacitor has failed or is currently underperforming, we can help. Call us today to schedule an appointment.