Common HVAC Noises and What They Mean

Common HVAC Noises and What They Mean

We all expect some noise out of our HVAC systems. In fact, if you’re feeling too cold or too hot, the sound of the HVAC system starting up can be one of the most comforting sounds of all. However, if the noise changes oddly or starts to interfere with daily activities, you don’t have to put up with the annoyance and worry. Instead, you can get some insights and contact us for some help identifying just what is going on.


HVAC systems are some of the hardest-working systems there are, mostly because their jobs are never done. When you think about it, it’s great that they run as well as they do for as long as they do. Here are some of the most common sounds people report to us and what is generally going on.


If you hear hissing coming from your system, it is usually one of two issues:

  • Misaligned air filters: the air filters in your vents are meant to create a seal so that all air has to pass through them rather than around them. Sometimes, air filters are the wrong size or have been installed correctly, which results in air escaping past them and creating that hissing noise you hear. Generally, it will be a light hissing noise rather than a loud one. Ensuring the filter is the correct size and that it has been installed correctly is an easy fix that should leave your system hiss-free.
  • Leaky ducts: old, broken, or badly-installed air ducts will leak air into your walls, which is where you’ll hear most of the noise. It’s not just annoying; it’s a compromise of your system and it wastes energy. Your HVAC system will have to work harder to get your home to the right temperature because it’s losing air into the walls.


If you’re heating rattling coming from your HVAC system, there are two common reasons that we’ve encountered:

  • Debris in the system: if you check your outdoor unit and find the noise is coming from there, it is possible that it just needs to be cleaned out. Outdoor units come with gratings designed to keep large debris out, but smaller pieces can get through, and over time, it can build up if you aren’t regularly maintaining your unit. To remedy this problem, the system needs to have the power cut and the debris removed. It is usually best to have a professional do this because debris often damages the unit and we can quickly fix any damaged components, ensuring the unit is good to go before we leave.
  • Damaged internal components: if you’re hearing rattling that comes from inside the unit or your home, gives an HVAC technician a call and turn the system off until he or she can check the unit out. Chances are good that the issue isn’t simple and would benefit from professional expertise.


We saved this noise for last because it is generally the most serious. Clanking noises generally mean you’ve got loose parts, and if you don’t get the problem addressed, they can cause expensive damage. Anything can be loose, like blades, pipes, or blow motors. If you hear clanking, you should turn your system off and give us a call so we can quickly identify and remedy whatever is going on.

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The average HVAC system lasts a great 15 to 20 years, and you can maximize yours by getting it cleaned and checked regularly. Ensuring the filters are clean as well as giving the system a break as often as possible will also keep it running strong for as long as possible.

Turn to the experts at DUCTZ for all of your HVAC and air duct cleaning in Palm Beach. We are here to help!

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