Duct & Furnace Noises Can Cause Concern, But Not All Mean Trouble

Posted on: November 17, 2015

It can be unsettling to wake up to strange pops and whistles on cold nights in your North Carolina home, but it’s not an uncommon occurrence in forced air HVAC systems. Duct and furnace noise may occur at any time, particularly right after a professional duct cleaning.

The good news is that it’s rarely a sign of ductwork damage or other problems, but the duct and furnace noise can be intrusive. If you think that you need help right away, you can contact Air Experts in Raleigh, NC now! Otherwise, read on to learn the most common types of noises and what you can do about them.

Popping Ductwork

Ducts that pops when the air turns on or off are simply flexing with the interior air pressure. It’s especially common after professional duct cleaning or furnace maintenance, as the entire system operates at its peak level when clean. Air filters aren’t clogged by any debris, ducts have nothing clinging to the sides to shield the walls or to slow airflow, and the blower motor or other components work together flawlessly.

Flexing ductwork won’t cause damage. In fact, most types of ducts have creases along the sides specifically to allow them to flex as needed. The only way to really fix this popping is by replacing the ductwork. You obviously don’t want to do that when you have fully functioning ducts in good repair, but here are some considerations when it’s time for a replacement:

  • Duct shape – Some shapes, such as rectangluar ducts, flex easily with air pressure. Stronger shapes such as circular ducts may reduce or eliminate flexing with their superior aerodynamics.
  • Thickness – Ducts come in a wide range of thicknesses, and larger or more powerful furnaces should have thicker ducts. Flexing ductwork may be an indication that the existing ducts are a little too thin, so opt for a thicker replacement.
  • Broken ductwork – If existing ducts aren’t creased, replacing them with a creased model may give the system a little more flex room without creating unwanted noise. This creasing is called “breaking” the ductwork.

If the popping becomes an issue before the ductwork needs to be replaced, discuss the problem with an HVAC specialist to explore other options that may work for your home.

Phantom Whistles in the Vents

Whistling around one or more vents can be among the most disruptive of all duct and furnace noise. Don’t worry, it’s not a ghost – and it’s usually not a difficult problem to fix, either. The sound you hear is usually caused by air that’s too restricted as it passes through heat vents or air supply registers. Check the vents for debris, replace any existing air filters that have clogged, and check that all of the covers fit tightly on their respective vents. Ensure that the louvers are either completely open or completely closed on all vent covers.

If all the vent covers are clean and in place but the system still whistles, check the blower motor. Some systems have multiple blower speeds. If yours is variable, turn the blower down a notch to see if a lower air volume solves the problem.

Diagnosing Noisy Furnace Problems

A boom or pop coming from inside the furnace may indicate a potentially serious issue. Most often, it’s caused by delayed burner ignition. In other words, the burners don’t light immediately after the gas turns on, or they don’t all light. As a result, gas builds up inside the heating element and produces a tiny explosion when the burners finally catch.

Delayed burner ignition can be caused by a faulty ignition, dirty burners, corrosion or buildup inside the furnace. Stand several feet away from the furnace, and have someone turn the thermostat up high enough to turn the furnace on. Watch the burners from a distance. If the fire takes several seconds to start and is accompanied by a pop or boom, you’ve confirmed that delayed burner ignition is the most likely problem.

Gas furnaces can be dangerous, so most home DIY enthusiasts shouldn’t attempt to work on them. Call your trusted HVAC technician and describe the duct and furnace noise, as well as your observations about the burners. An expert technician will inspect and clean the furnace, and then repair any faulty parts.

Contact Air Experts for Furnace or Duct Services in Raleigh, NC Today!

For additional help or information about duct and furnace noises, contact Air Experts online today, or call us anytime at 919-480-2727! We provide comprehensive services for all your HVAC needs in Raleigh-Durham and surrounding areas.

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