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Are Furnace Noises Making Your Heating System Sound Pained?

  • January 21, 2015

furnace noisesSince furnaces are mechanical in nature, they have components that turn on, run and turn off. During this cycle time, it’s not unusual to hear noises coming from the furnace or ductwork. In almost every instance, these noises are perfectly normal and in no way compromise the safety or effectiveness of the furnace.

Here are some of the most common furnace noises that you might hear during start-up or when the fan is blowing.

Popping or Banging Noises

For a few minutes after start-up, you may hear popping or banging noises. In virtually all cases, this is merely the ductwork starting to expand.

As the air blows through cold ducts, the warm air begins to expand the metal, and as the metal flexes, it may pop or bang. This is an especially common occurrence with square or rectangular ductwork, particularly if a lighter gauge of sheet metal has been used. The lighter the gauge of sheet metal, the more flex as it expands, and the greater the popping or banging noise as it heats up.

Using a higher gauge of sheet metal helps, but the best solution is using round ductwork that symmetrically expands and limits popping or banging noises.

Whistling Noises

Whistling is also a common furnace noise that generally begins in the ductwork. Clean ducts will sometimes whistle as the unimpeded air blows through. But dirty ductwork can also whistle as air blows past dust and dirt inside the ducts. Changing furnace filters regularly will eliminate most dust and dirt build-up and will probably eliminate ductwork whistling.

Half-closed vents may also cause whistling, so if whistling occurs, always check the vents to make sure they’re wide open.


A booming sound as the furnace starts may be a delayed ignition or blocked furnace burners. In this case, an experienced technician should be consulted to ascertain the problem.

When you have questions about furnace noises, the professionals at Comfort Services Inc. are here to help. We can give you the answers you need and service Aberdeen, North Carolina, and the surrounding areas.

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