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What Is the Difference Between the Start and Run Capacitor?

Your air conditioner is vital to maintaining comfort in your home, especially during hot summer days. When you switch on your AC, numerous components work together to cool your space effectively. Among these, capacitors play a crucial role. These components are essential for powering your air conditioner, enabling it to operate efficiently. Without capacitors, your system simply couldn't function.

There are two main types of capacitors within your AC unit: start and run capacitors. Each serves a unique function that is vital for the proper operation of your air conditioning system. Understanding the role of each type of capacitor will help you better diagnose issues and ensure your unit receives the appropriate maintenance or repairs.

In this article, we’ll explore:

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What Does a Capacitor Do?

A black and white diagram showing in red where the AC Capacitor part is located

An AC capacitor is a cylindrical device that stores energy. Its goal is to supply your air conditioner's motor with the power it needs to function properly. Without a properly working capacitor, your AC unit must work much harder to cool down your home. This can cause your energy bill to spike and strain your unit considerably. It's important to address any issues with your capacitor immediately because they can impact your entire HVAC system.

Start Capacitors: The Initial Boost

The start capacitor is responsible for providing the initial surge of energy that your AC unit needs to run. This electrical push comes as a current that activates the motor rotation. As the current gradually builds up, the motor begins to rotate with the field of current. Start capacitors also allow the motor to be quickly cycled on and off. They stay energized until the motor reaches 75% of its maximum speed and are removed from the circuit to prevent an overload.

Run Capacitors: Maintaining Efficiency

Unlike start capacitors, which only provide an initial burst of energy, run capacitors are designed for continuous use. They remain energized the whole time the AC motor is running. Once the start capacitor provides that initial current to get the motor going, the run capacitor boosts the current to keep the air conditioner working. The main purpose of a run capacitor is to maintain a charge to keep the AC unit performing at its best.

How Each Type Works Together

Both capacitors work in tandem to keep your HVAC system functioning at optimal performance. The run capacitor essentially picks up where the start capacitor left off and provides supplemental energy to keep your AC running. Without the run capacitor, the start capacitor would eventually burn out trying to maintain such a high level of energy, which could lead to electrical issues. Likewise, the run capacitor relies on the start capacitor to set the whole process in motion before it can continue.

Signs of Faulty Capacitors

Don't overlook the signs of malfunctioning capacitors in your air conditioner. Even seemingly minor capacitor issues can escalate into more severe problems that are costly to fix. Here are some clear indicators that your AC capacitors may need professional attention:

  • Sudden Increase in Energy Bills: An unexpected rise in energy costs can indicate that your AC is working harder than normal, possibly due to failing capacitors.
  • Humming Noise: A continuous humming sound from your unit suggests that the capacitor struggles to start the AC motor.
  • Inability to Turn On: A faulty start capacitor could be the cause if your air conditioner doesn't start.
  • Unexpected Shut-Offs: Your AC turning off on its own might indicate a problem with the run capacitor, which helps maintain the motor's operation.
  • Burning Smell: Any burning odor emanating from your unit is a warning sign of potential electrical issues, including capacitor failure.

If you notice any of these symptoms, it’s crucial to contact a professional HVAC technician who can accurately diagnose and resolve the issue to prevent further damage and ensure your system’s longevity.

Keep your AC unit running smoothly with professional service.

Since 1955, the team at George Brazil has taken pride in its reputation as a top-tier HVAC company. We offer fast, convenient scheduling to take all the hassle out of the process. When you schedule an AC repair with us, you can rely on us to fix your unit in just a single visit.

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