Here's How to Repair a Noisy Heating System

A home high efficiency furnace with a residential gas water heater & humidifier.

During the winter, your heat pump, boiler, or conventional forced air furnace switching on makes a common, comforting humming sound. When the system starts up and that normal humming noise begins, you know that heat is on the way to warm up your space. Unfortunately, furnaces can develop problems, and you may notice that your heating system makes noise you haven’t heard before.

Unusual noises like loud booms, banging noise, rattling, or whistling noise coming from the furnace can be frightening, but some of these sounds are harmless. However, it’s always important to reach out to Thomas & Galbraith Heating, Cooling & Plumbing if your furnace or air conditioning unit starts making noise you haven’t heard before. An HVAC professional can perform important checks and diagnostic tests to rule out more serious problems, such as a damaged blower, motor, or ball bearings. However, this guide will help you to know what the problem might be, and how a technician will resolve the issue at hand.

What Could Cause Extra Noise Coming from a Heating System?

Anytime you notice strange noises emanating from your heating system, there may be something wrong, and it’s a good idea to look into the issue. Never assume that the system is operating smoothly when it is making a noise you have never heard before. Some problems may require simple repairs, while others require professional service to fix. Find out what the sounds coming from your furnace mean, and what you need to do to fix it.

Banging Sounds

Anytime your boiler, furnace, or heat pump creates a loud banging noise, it could mean these problems are present:

Malfunctioning Ignition

Ignition issues are one of the top causes of loud banging noises coming from furnaces. Oftentimes, this sound is caused by a buildup of gas within the furnace’s combustion chamber, resulting in a miniature explosion inside your heating system when the unit does light. Sometimes this issue is caused by dirty ignitors, a clogged burner, gas pressure problems, or a weak pilot light flame. Place a service call to have a professional HVAC technician inspect and test your furnace whenever you hear loud bangs coming from your furnace.

Air Trapped Inside of Pipes

Banging sounds can also occur when air becomes trapped inside the lines of boiler heating systems. To fix this issue, you may need to bleed the pipes. Here are instructions for taking care of this routine task:

  1. Turn off the breaker to your boiler system to cut the power.
  2. On each radiator in your home, there should be a valve below the radiator end cap. Turn the valve counterclockwise to release air from the lines.
  3. After air escapes and water starts to trickle from the valve, make sure to close it again.
  4. Use the steps above to bleed air from all of the radiators in your home. If you do not feel comfortable working with your radiator, an HVAC professional would be happy to help.

Dirty Heat Exchanger

Banging noises can occur when the heat exchanger inside your furnace becomes encrusted with limescale. While you may be able to spot a chalky white accumulation on your heat exchanger, you shouldn’t attempt to clean it on your own. Instead, order a service call. When limescale builds up within a boiler, the system can create a “kettling” noise, which sounds like boiling water inside a teapot.

Normal Expansion and Contraction Inside Ductwork

As ductwork cools after your furnace, heat pump, or boiler runs, the metal can contract and bend slightly, producing a banging noise that reverberates throughout your home. When your heating system starts again, the metal may cause an expansion reaction in the ducts, generating the same type of sound. While it may seem jarring, this type of banging sound is harmless, and will not hurt your furnace.

Grinding

Metal on metal grinding sounds could mean you have unlubricated ball bearings. This common problem often stems from a lack of routine tune ups, so schedule one if you notice the sound. Professional technicians can lubricate ball bearings and inspect your blower and motor for damage.

Squealing

Your blower motor and fan inside your furnace are connected by a fan belt, which can become cracked, broken, or slipped during normal operation, producing a squealing noise. Follow these steps to check your fan belt for damage.

  1. Turn off your furnace by flipping the breaker.
  2. Look for the access panel that hides the blower compartment. You should see the motor and fan belt.
  3. Using a flashlight, inspect the fan belt for signs of wear and tear. You may spot fraying edges, cracks, or burn marks. If the belt is damaged, you may need a new one. You can remove the van belt by loosening the bolt on the blower motor. Take the belt with you to the home improvement store to make sure you purchase an identical replacement and switch out the belt. Remember, you can always call a professional for help.
  4. The belt shouldn’t have more than ½ an inch of slack in any direction. If the tension seems too lose, you can remove extra slack by tightening the bolt on the blower motor.

Rattling

Rattling usually means that one or more parts, screws, or replaceable panels are loose on or within your furnace. Check your furnace cabinet panels for signs of loose access doors and replace any missing screws. If all of the access doors are firmly in place and don’t appear to move at all when the system runs, the issue could stem from loose or damaged heating components. Place a service call to have a professional check your system if you can’t find an obvious reason for the rattling.

Resolve Furnace and Heating System Noises with Help from Our Team!

Noisy furnaces, heat pumps, or boilers can be nerve-wracking, but don’t let that extra racket scare you. Our experienced, NATE-certified heating contractors can inspect, diagnose, and resolve furnace issues that cause extra sounds to create a quieter, more serene home. Call us here at Thomas & Galbraith Heating, Cooling & Plumbing for help with your furnace when you need it.

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