Why Is My RTU Making Loud Unusual Noises?

Your rooftop unit (RTU) runs almost constantly, so a certain amount of background hum is normal. But when the sounds change, get louder, or turn into something you’ve never heard before, that’s your system telling you something is wrong. As a property owner, you should understand:

• Which RTU noises point to which problems
• What common causes of noises are
• How these sounds affect performance
• When you need to hire a professional

Here at Van Drunen Heating & Air Conditioning, we want you to understand when you should be concerned about your RTU making noises. If you need further assistance or are worried about your unit, feel free to contact our team.

What Do Different RTU Noises Actually Mean?

Not every strange sound means the same thing. The type of noise your RTU makes is often the first clue about what’s going wrong. Here are a few examples of noises that may point to specific problems:

• Banging or clanking usually points to a loose or broken part, such as a fan blade, motor mount, or compressor part, hitting other surfaces during operation.
• Squealing or screeching is often due to a slipping belt or a bearing that’s starting to fail in the blower motor.
• Rattling typically caused by loose panels, screws, or debris that has gotten inside the unit.
• Humming or buzzing can indicate an electrical issue, a failing contactor, or a refrigerant problem.
• Clicking repeatedly during startup or shutdown may signal a failing relay or control board

Each of these sounds is worth paying attention to. Left alone, minor noise issues tend to become bigger, more expensive problems. It’s important that you reach out to a trusted company to prevent small damage from becoming big issues.

What Are the Most Common Causes of RTU Noise Issues?

Once you know what you’re hearing, the next question is why it’s happening. Most RTU noise problems come down to a handful of common causes:

• Worn belts and bearings: Over time, belts stretch and crack, and bearings wear down.
• Loose components: Vibration from years of regular use can loosen screws, panels, and motor mounts, which then rattle or bang while the system runs.
• Debris buildup: Leaves, dirt, and other debris can collect inside or around your RTU, especially after storms. Even small amounts of buildup can interfere with fan blades and other moving parts.
• Refrigerant issues: Low refrigerant levels or refrigerant leaks can cause hissing or bubbling sounds.
• Dirty or clogged coils: When coils are heavily fouled, the system works harder than it should, which can create unusual operational sounds.

Regular RTU maintenance goes a long way toward catching these issues before they start making noise. Many of these problems are entirely preventable with routine inspections and cleaning.

How Do RTU Noise Problems Affect System Performance?

A loud RTU isn’t just annoying. The problems causing those sounds usually have a direct impact on how well your system performs. Here are some negative effects of not addressing issues: 

• Reduced efficiency: When worn parts force your RTU to work harder, energy consumption goes up, often noticeably on your utility bills.
• Inconsistent heating and cooling: A failing blower motor or damaged fan blade won’t move air properly, leading to uneven temperatures throughout the building.
• Increased wear on other components: One failing part puts stress on the components around it. A worn belt, for example, can strain the motor it’s connected to.
• Higher risk of full system failure: A system running with unresolved mechanical problems is far more likely to break down completely, often at the worst possible time.

Basically, unusual sounds are a symptom of something that’s already affecting performance, even if you haven’t noticed the effects yet. An experienced technician can help you determine the best solutions.

When Do Unusual RTU Noises Require Commercial HVAC Service?

Some noises are more urgent than others. Here’s a brief guide to help you understand when you need these services.

Call for service right away if you hear:

• Loud banging or metal-on-metal clanking, which can signal a broken component causing damage inside the unit
• Hissing or bubbling sounds, which may point to a refrigerant leak
• Burning smells paired with unusual sounds, which could indicate an electrical or motor problem

Schedule an inspection soon if you notice:

• A new squealing or screeching sound that wasn’t there before
• Persistent rattling that doesn’t go away after a quick visual check for obvious debris
• Clicking that happens repeatedly or at unusual times during operation

Monitor and mention at your next maintenance visit if you hear:

• A slightly louder hum than usual, with no other symptoms
• Occasional, brief rattling that seems weather-related

RTUs are investments, and catching a problem early almost always costs less than waiting until something breaks. If you’re not sure what’s going on, it’s always best to get it checked out.

Don’t Let Small Sounds Become Big Repairs

If your commercial RTU is making noises that have you concerned, the team at Van Drunen Heating & Air Conditioning is ready to help. We’ve been serving businesses in Illinois for over 50 years, and our technicians know commercial HVAC systems inside and out. Contact us today and schedule a service visit.