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Commonly Reported HVAC Problems:

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Noisy Air Vents, High-Pitched Noise:

installing a ceiling register

All air vents, meaning supply registers, ceiling diffusers, floor vents, and return grilles make some noise when the system fan is running. This is normal. Some systems are louder than others. Some systems are much louder than others.

For example; a house with plenty of return air ducting, including return vents in every room will probably be quieter than a system with just one large return grille cut directly into the return duct of the equipment. There is nothing technically wrong with the latter, it is just a less expensive system to install and is a very basic approach to ducting the equipment. The downside of course is that it may be loud!

The most common complaint we get on this matter is usually from return vents making a high-pitched, tuning-fork type of sound. This usually, not always, but usually, indicates a lack of return air. The system needs to pull more air so the pressure and velocity increases, thus increasing the sound level. By adding more return air, the pressure drops, and the system doesn't have to work as hard, and it quiets down.

Now, why do we have a lack of return air? The ductwork could be undersized or not installed properly. But it could also be as simple as a blocked air filter. Maybe someone closed off too many vents. Yes this could cause the problem as well. The system is designed to move a certain amount of air. By blocking either the return or supply vents, (anything that restricts the airflow) it causes a pressure problem - increasing the sound level. We have seen furniture blocking return vents, restricting air flow.

Other vent-related noises include rattling and or flapping sounds - which are usually due to debris in the duct... screws, nails, small toys, plastic, construction materials, saw dust, and so on. So after checking all the obvious things, the next step would be to have a technician inspect the system's performance.

checking static pressure

Hannabery's service technicians can not only check the equipment, but can diagnose the ductwork for proper air-flow. Along with system pressures and temperature splits, they can check for proper CFM and static pressures to determine if the system is moving the air properly.


Below is a list of possible causes. Items in red usually require a service call. Items in blue however can be addressed, some even fixed by the homeowner.


Red = Professional fix | Blue = Homeowner fix

  • Undersized ductwork
  • Restricted ductwork
  • Faulty grille
  • Large return very close to unit
  • Filter blocked
  • Return vents blocked or shut off
  • Supply vents blocked or shut off
  • Dampers shut off
  • Debris in ducts - may need professional cleaning

Please keep in mind that the information found on our website is provided free of charge and Hannabery HVAC does not assume any liability resulting from the information we provide. We hope this information helps, but please note that these are just rough guidelines, and not all possible situations are covered. Your HVAC system should be inspected and repaired by a trained technician.

Commonly Reported HVAC Problems

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