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Why Does My Circuit Breaker Panel Make a Buzzing/Humming Noise When My AC Comes On?

When it comes to electricity and wires, people are skittish.

So if you hear buzzing/humming noises coming from your circuit breaker panel (aka, the main electrical panel) every time your AC kicks on, you're probably a little nervous (as you should be).

To help keep your AC healthy and your family safe, we’ll cover the main reasons your electric panel is making this buzzing/humming noise when your air conditioner is running.

Are you in Phoenix or a surrounding area looking for an air conditioning repair service? Ask one of our experts for help.

A vibrating/buzzing noise is normal if...

...it's not very loud

First, we want to possibly ease your concerns. If the humming or buzzing isn’t very loud, this is normal.

Energy comes in and out of the panel at a rapid pace and this creates vibrations in the breaker that you can hear coming from inside the panel.

...it's only heard as the AC starts up

If the buzzing noise occurs right as the AC kicks on but stops once your air conditioner is running steadily, this is normal.

You see, large motors (like the one that runs your AC) draw a LOT more energy at startup than it does when it's steadily running. And this extra power is probably pushing your AC breaker to its limits, which is causing that buzzing noise.

But the AC motor should only pull extra power for a few seconds, meaning the buzzing noise should stop within 30 seconds of the AC kicking on.

Hear a loud buzzing noise that persists as the AC is running steadily? That's not normal. Keep reading to determine what AC or electrical problem you may have...

Hear a loud buzzing noise? You might have a bad AC capacitor

Remember how we explained that large motors draw a lot more power as they start up? Well, your AC actually has a sidekick that provides that extra "oomph" it needs to kick on quickly. That sidekick is called the AC capacitor—and if the capacitor is bad, it could be causing that loud buzzing noise.

Location of an AC capacitor in an AC system

Location of your AC capacitor

The capacitor is basically a huge battery that stores energy and sends an electrical jolt to the AC motors when they kick on. The bad news is that, just like normal batteries, capacitors can go bad or run out of juice. And, when that happens, sometimes the AC will struggle to start.

If an AC has a bad capacitor, it may continuously draw more power than it should, which creates that buzzing noise. But along with that buzzing noise, you may hear a few clicking noises at the outdoor unit (that's the AC getting the call to turn on) followed by the hum of the AC motor. Sometimes, the AC will come on for a few moments and then shut off again.

If it's not replaced soon, a bad capacitor can ruin the AC's compressor (which is a very expensive repair). So, if you hear the tell-tale noises of a bad capacitor, call an AC tech immediately.

Other electrical problems that cause loud buzzing noises:

  1. A circuit breaker is failing to trip. A circuit breaker that isn't tripping when it's supposed to will allow an unsafe amount of current to run through your home's wiring. This high level of current can cause a loud buzzing noise and requires professional repair/circuit replacement.
  2. A loosely connected wire. If a wire connected to a circuit breaker isn’t connected securely (or it’s damaged), it can cause a buzzing noise (and create some sparks, too).

Just like the bad breaker, this is dangerous and needs a professional’s attention ASAP.

Need help?

If you live in the Phoenix metro area and have a loud buzzing/humming noise coming from your AC, we can help. Our techs will come out to inspect your system, determine the problem and offer a same-day solution.