What Does It Mean When Your HVAC Ductwork Makes Noises?

Posted by Ohio Heating

Mar 26, 2016 10:04:39 AM

Your heating and cooling system consists of the heating and cooling units, blower, air ducts, return grills, vents and the air filter. Any of duct_aluminum.jpgthese components can make some strange noises if something is wrong.  The source of the duct and furnace noise can sometimes be hard to find. 

The most common noises are from metal ducts. Ductwork comes in three different shapes: circular, square and rectangular. Each shape has a different threshold for the amount of pressure (CFMs) it can handle. In some cases, excessive air flow can cause whistling. Pressure differences between the supply and return ducts can move their walls in and out, resulting in a rumbling sound called "oil-canning." 

Ductwork can also carry the sound of a noisy blower through your entire house.  You might also hear some innocuous creaking, but if the duct is rubbing against wood, it might suddenly "pop" and reverberate, then pop again as the metal cools. 

Commercial ductwork is stronger and thicker and less likely to react and pop under pressure. While it can be annoying, the popping is not dangerous. It is just your ducts being exposed to more pressure than they can handle without expanding.

It is possible to reduce the amount of popping by using round ducts, square ducts, or simply increasing the gauge of the metal used. When using rectangular ducts, they can be constructed with crease or bend in the long side. This is called “breaking of the ductwork”.  When a manufacturer “breaks” the ductwork he puts a crease or bend in the sheet metal before shaping and assembling it to the rectangular shape. This crease will sit on the wide side of the rectangle and it effectively stiffens and strengthens that larger side. Increased strength will enable it to withstand higher pressure before it “pops”.  At Ohio Heating, we fabricate custom ductwork and we utilize the crease to strengthen your ducts.

Another common problem is undersized ductwork, which causes the ducts on the supply side to expand as they pressurize. This in turn creates a small vacuum on the return side. When this happens, the ducts will expand and contract.  As the blower turns on, the metal ducts will start to make a banging sound.

If you hear ticking noises, these are usually from the expansion and contraction between the hangers and the ductwork itself. One remedy is to insulate the ductwork from the hangers with rubber cushions to cut down on the noise or it may even resolve the problem entirely. 

Another common issue comes from the internal and external components being linked together. They both carry a lot of acoustic noise, and if they’re on the same path, the duct work will carry the vibrations of the acoustics into the home, causing howling, buzzing and whining noises. You should check to see if the internal duct system is connected on the same pathway as the external system. 

At Ohio Heating, we know that your HVAC ductwork is a major component of your HVAC system working efficiently and quietly.  HVAC system noise can be annoying but it may also be a symptom of something wrong.  your Our custom sheet metal shop can fabricate custom ductwork that meets the specific requirements for your home and your furnace and air conditioning units.  If you're experiencing excess noise from your HVAC equipment, you may need to have it checked by a professional.  Our NATE certified technicians can pin point the problem and provide a solution.  Give us a call at 614.863.6666 to schedule an appointment.

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Topics: custom fabrication, ductwork, metal shop, HVAC noise, custom ductwork

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