Strange Sounds in Your HVAC’s Duct System

Both your furnace and your air conditioner rely on your home's duct system. A special blower fan pushes conditioned air along the ducts into the rooms of your home. Ideally your duct system should accomplish this task with relatively few noises at all. Depending on your proximity to the blower motor, you may hear a muted hum — but hopefully nothing else.

Unfortunately, however, duct systems don't always behave so considerately. In many cases, ducts produce odd or unusual noises that can interrupt the flow of life in your home. If you would like to boost your ductwork diagnostic skills, keep reading. This article looks into three common culprits behind unusual duct noises.

1. Lack of Dampers

Most duct noises stem from the air handler — that is, the blower motor and fan used to distribute conditioned air. The air handler naturally produces vibrations as it runs. These vibrations often travel through the relatively thin and reverberant walls of your ducts, contributing to excess levels of noise inside of your home. Fortunately, you can effectively eliminate air handler vibrations through the installation of a vibration dampener. An HVAC technician installs this component, also sometimes referred to as a vibration isolator, between the air handler's supply plenum and the supply duct. There the rubberized fabric of the dampener effectively stifles any vibrations before they reach the ducts.

2. Filter Issues

No matter how well isolated your air handler's vibrations, your system may still produce unusual noises as the result of other factors. One frequent problem has to do with the air filters installed in your HVAC system. Incorrectly sized or excessively dirty filters can lead to a wide range of unusual noises, from clunking to whistling to whining.

Undersized filters often lead to strange sounds as unfiltered air whips around the edges of the filter. Homeowners often struggle to find an air filter that fits their system perfectly. A reputable HVAC contractor likely has the right size on hand. If not, the technician can often have a custom filter created just for your system.

To keep odd sounds at bay, you must be proactive about replacing old filters. As an air filter becomes progressively choked with dirt and debris, it begins to negatively affect airflow. Such restrictions throw off the pressure inside of your ducts, often leading to annoying noises.

In addition, such clogs will force your system to work harder than it should, thus driving up costs and putting more stress on your furnace.

3. Poor Sizing

Another common cause of noises involves incorrect duct system sizing. Undersized ducts, in particular, tend to produce audible problems. You may notice that your ducts seem to whistle every time the blower system comes on. Such whistling happens as excessive amounts of airflow move through your insufficiently large ducts, leading to increases in both pressure and velocity.

This issue most often crops up in the wake of a furnace upgrade. Many homeowners select new furnaces that simply have too much power for the existing duct system. Variable-speed furnaces tend to be especially problematic. Such furnaces, designed to operate at different speeds depending on heating demand, often increase their power to compensate for undersized ducts.

Unfortunately, this overcompensation only makes the whistling sounds worse. Moreover, your system simply won't provide efficient results. You'll end up spending far more than you should to heat your home, while also subjecting your furnace to unnecessary wear and tear. Consult an HVAC professional to determine the ideal duct size for your furnace.

Duct noises can cause a lot of frustration, but in most cases the problem has a relatively simple solution. For more information about how to keep your system whisper quiet, please contact the Chicagoland HVAC pros at Always Ready Repair.