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Why Is My Furnace Making a Loud, Rumbling Noise?

A furnace that makes loud rumbling noises is a cause for concern among Birmingham area homeowners – as is any unexpected, new noise from your home’s heating equipment! New noises, especially those loud enough to be disruptive, should never be ignored. In our most recent blog, the technicians at Douglas Cooling & Heating discuss what a loud, rumbling noise typically tells you about your heating system and what to do when you first hear it.

Causes of a Loud, Rumbling Noise from Your Furnace

The range of potential problems in play when you have a furnace making loud rumbling noises varies from minor to serious and demands immediate attention. Rumbling is typically associated with a few specific heating system issues, but there are some other malfunctions that have the potential to produce a rumbling noise.

Dirty Burners

The most common reason for this noise is that the burners are dirty. Soot collects on the burners during normal furnace operation and should be cleaned regularly. Douglas Cooling & Heating does this as part of your annual furnace tune up. If the burners do not receive a regular cleaning, the soot can block airflow. In this case, the burners don’t receive adequate airflow for combustion, which leads to a furnace making loud, rumbling noise. The rumbling occurs when a heating cycle first starts and during furnace operation.

Yearly furnace maintenance typically prevents this problem. If you haven’t had a furnace tune up recently and hear this noise, inspect the burners to see if soot is present on or around them. Call your HVAC technician to clean your furnace burners if they are covered in soot.

Pilot Light Problem

If your gas furnace is more than 15 years old, it probably uses a pilot light to initiate combustion. This component can cause a furnace to make rumbling noises when it isn’t properly adjusted or is covered in soot. The sound occurs while the furnace runs and even after a heating cycle is completed.

Take a look at the pilot light – if the flame appears low or the component has visible soot, this could be the cause of this concerning noise. Call your HVAC technician to inspect, clean, and properly adjust the pilot light. If your heating system still operates using a pilot light, you’d be wise to start investigating replacement options before the aging system fails on you.

Dirty Draft Inducer Motor

A furnace’s draft inducer sits near the heat exchanger. It moves combustion gases into the flue pipe so they are safely exhausted out of the home, preventing exposure or explosion inside the heat exchanger. It also directs oxygen to the burners to aid in their efficient performance. When dirty or loose, this component can lead to a rumbling noise when the system first starts up for a heating cycle.

Call your HVAC technician to inspect the furnace and its draft inducer. Your technician will clean the component and ensure it is properly secured within the system.

Loose Panels

The exterior access panels of the furnace can become loose and produce noises as the system operates. Typically, they bang around, but if the screws are only a little bit loosened, rumbling can occur.

Check the exterior of the furnace and ensure all metal panels are properly fit and secured. Tighten screws as needed.

Cracked Heat Exchanger

A cracked heat exchanger is perhaps the most serious issue a furnace can have, requiring immediate service with discontinued use until repair or replacement is completed. A crack in the heat exchanger allows carbon monoxide to escape and mix into the air supply rather than venting safely outdoors, creating the potential for deadly carbon monoxide exposure inside.

Usually, the sound produced is more of clink or rattling noise, though a low-pitched rumble can occur in some units. If you do not find signs of the other causes outlined above, a cracked heat exchanger may be the source of the sound. Turn off your furnace, cut its gas supply, and call your HVAC contractor for emergency furnace repair.

Furnace Repair from Douglas Cooling & Heating

Furnace sounds should never be ignored. If your furnace is making a loud rumbling noise, let Douglas Cooling & Heating get to the bottom of the issue today! We will find the cause of the sound and perform the necessary repairs to restore safe, efficient, and quiet operation! Call us to schedule service.

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