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Why Does My Circuit Panel Make Buzzing & Humming Noises When My AC Comes On?

An HVAC tech wearing a yellow hard hat and overalls working on a circuit panel

It is common for individuals to have concerns regarding electricity and wiring. Electrical fires and shocks are fairly common when home systems are improperly maintained. When you run your air conditioning unit, it is understandable to feel apprehensive if you notice buzzing or humming noises emanating from your circuit breaker panel, also known as the main electrical panel. But not all noises mean there's a problem.

To give you peace of mind, we'll discuss the primary causes of the buzzing or humming noise that can happen when you turn on the AC:

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When You Should Be Concerned

Did you know that most things that use electricity release a faint vibration or very quiet hum? The more electricity something uses, the more noise it makes. If the hum you hear is quiet, it's likely normal. If the buzzing is loud enough to interrupt a conversation, or you hear it when the house isn't silent, it could be a cause for concern.

If the buzzing noise stops after a few minutes, that's also normal. When AC units first turn on, a big surge of electricity and moving parts start to generate noise. The extra power draw fades off seconds after your machine starts running, so you can probably relax if the buzzing noise stops after a minute.

You should call in an HVAC technician from George Brazil HVAC if the noise is loud and persistent. It could mean several failing parts, and repairs need to happen quickly.

Bad AC Capacitor

Outdoor unit on a concrete pad in a grassy backyard.

Why does my circuit breaker panel make a buzzing/humming noise when my AC comes on? A faulty AC capacitor could cause it. Allow us to explain. Large motors, like those needed when your system starts up, require significant power. A capacitor provides air conditioners with the extra power needed for a quick start.

The capacitor acts as a large battery that stores energy and delivers an electrical jolt to the AC motors at start-up. However, like any battery, capacitors can deteriorate or run out of power, causing your AC to struggle to start and potentially leading to annoying buzzing noise.

A bad capacitor can cause your AC to continuously draw more power than necessary, creating a buzzing noise but also potentially causing damage to the expensive AC compressor. Don't let a faulty capacitor ruin your AC. If you suspect it may be the source of the buzzing noise, contact an AC technician immediately for a replacement.

Circuit Breaker Failing To Trip

A circuit breaker is designed to trip or disconnect the electrical current when the electrical load exceeds the rated capacity of the circuit. If a circuit breaker fails to trip, it is not properly disconnecting the electrical current when there is an overload. This can lead to a buzzing noise for a few reasons:

  1. Overheating: When a circuit is overloaded, and the breaker fails to trip, the excess electrical current can cause the wiring and electrical components to overheat. This can create a buzzing or humming noise as the wires expand and contract due to the heat.
  2. Arcing: When the circuit breaker fails to trip, the electrical current can arc or jump from one conductor to another. As the electrical current jumps the gap, this can create a buzzing or humming noise.
  3. Motor Overload: If the circuit breaker serves an electric motor, such as an air conditioning unit, and it fails to trip, the motor may be overloaded and start to make a buzzing noise.

Loose or Exposed Electrical Wires

Loose wires can create an intermittent electrical connection, which can cause arcing and create a buzzing or humming noise. Arcing occurs when an electrical current jumps through the air instead of flowing through a conductor, and it can generate heat, sparks, and noise.

Exposed wires can also create a buzzing sound if they come into contact with other materials, such as metal, or if they are in close proximity to other wires. The contact or proximity can cause arcing, generating heat and noise. Additionally, if the exposed wires carry an electrical current, they can cause electrical shock or electrocution.

Faulty Thermostat Parts

A woman pressing the down button on a thermostat with her right hand.

A faulty thermostat can potentially cause buzzing in your electric panel. If the thermostat is not functioning properly, it may send incorrect signals to the air conditioning unit, which can cause the unit to turn on and off frequently. This can cause the electric panel to buzz as the circuit breaker repeatedly switches the current on and off.

Broken AC Condenser Fan

The condenser fan is responsible for blowing air over the condenser coils, which helps to release heat and cool the refrigerant. If the fan is not working properly, it can cause the condenser coils to overheat, which can cause the circuit breaker to trip and turn off the power to the AC unit.

It can create a buzzing noise when it trips by switching the current on and off. Additionally, if the fan is making a grinding or scraping noise, this can also create a buzzing noise in the electric panel.

It's important to note that a broken AC condenser fan can also cause other issues, such as reduced cooling efficiency, higher energy bills, and potential damage to the compressor. It's important to address this issue as soon as possible and get it fixed by a professional to prevent any further damage or issues.

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