Fix Your Heating System if It's Making Noises While it Runs

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

When your furnace, boiler, or heat pump turns on, you might be used to the common rustle of warm air rushing through your vents. However, if that humming sound has been replaced by other noises coming from the furnace or air conditioning system, there could be a problem.

Loud booms, banging noises, rattling, or whistling noises can be nerve-wracking and may occur at unusual times, prompting you to take a second look at your heating system. While some noises are normal and don’t indicate a deeper problem with your furnace, others may indicate problems with your ductwork, blower, motor, fan, heat exchanger, or burner. If your heating system is trying to tell you something, Jarboe’s Plumbing, Heating & Cooling is here to help. Our professional technicians are always available and can come out to diagnose and resolve heating problems in your home in no time. Until then, here are a few common reasons your furnace might be making extra sounds.

What Causes Some Heating Systems to Make Extra Noise?

When your furnace starts up, you may hear a click coming from the thermostat, followed by the gentle humming sound of your furnace starting up, and then the sound of air moving through your metal ductwork. Anytime you hear anything unusual, there may be problems with your furnace, heat pump, or boiler. Sometimes, parts within your heating system can break or malfunction. Here are a few of the noises you may hear if something goes wrong, and how a technician may repair broken heating systems.

Loud Bangs

Loud banging sound coming from your boiler, heat pump, or furnace can be caused by these problems:

Ignition Problems

Loud banging noises typically indicate problems with the ignition, since the noise can be caused by a buildup of gas and a sudden ignition. Problems with the ignition components, such as dirty ignitors or a dirty burner, can cause a buildup of gas inside the combustion compartment, and when the heating system ignites, it can signal a larger-than-normal explosion inside your furnace that creates the sound. Since this issue can be dangerous, always call a professional if you notice a banging noise. The burner network inside your ignition unit may need to be cleaned, or the gas pressure or pilot light flame may need to be adjusted.

Air Stuck Inside Pipes

Boiler heating systems can also create loud banging noises, but for another reason. Air can become trapped inside of the pipes in your home, resulting in pressure changes that create noise. To remedy this problem, you can bleed the pipes.

  1. Turn off your boiler system by cutting the power.
  2. There should be a valve below the radiator end cap. Turn it counterclockwise to release air pressure.
  3. You may hear air escape from the valve, and a trickle of water may follow. Close the valve when water starts to escape.
  4. Repeat these instructions to bleed all the other radiators in your home.

*Note: Anytime you are uncomfortable working with your furnace or radiator, an HVAC professional can help.

Limescale Accumulation on Heat Exchanger

Sometimes, banging sounds are caused by a buildup of limescale within your boiler on the unit’s heat exchanger. This issue isn’t something you can repair on your own, and you will need professional service to remove the accumulation. In a boiler, the system may create a whistling noise that sounds like hot water boiling in a teapot if limescale buildup is present.

Expansion Inside Ducts

Between heating cycles, your ductwork can become cool, and contract slightly. When your furnace starts up, it can trigger an expansion reaction of the metal ducts, producing a loud bang. While it may sound scary, this type of banging noise is normal, and may repeat when the heater turns off and the metal ducts contract again.

Grinding Noises

Your furnace’s blower fan operates using ball bearings. If these bearings don’t have adequate levels of lubrication, they can cause a metal on metal grinding sound. If you hear a grinding noise, your furnace may be due for a tune up. Professional HVAC technicians can check and lubricate bearings and ensure that the motor and blower haven’t been damaged.

Loud Squealing Sounds

Squealing noise coming from a heat pump or furnace can signal an issue with the blower compartment. Sometimes, this issue is caused by a damaged or slipped belt. Follow these steps to check your fan belt:

  1. Shut down your furnace.
  2. Open the blower compartment panel. You should be able to see your fan belt and motor.
  3. Look for signs of belt wear and tear. You may see fraying edges, cracks, or burn marks. If the fan belt is visibly damaged, it may need to be replaced. Place a service call to have an HVAC professional tackle the job for you or take the old belt to the hardware store with you to make sure you purchase the right size.
  4. Anytime the belt has extra slack in the line, it may need to be tightened. As a general rule of thumb, there shouldn’t be more than ½ inch of give in any direction. If the tension is loose, turn the bolt on the blower motor to tighten it.

Rattling Sounds

Anytime you hear rattling coming from inside a furnace, it could mean that something is loose from within your system. Sometimes, the issue is as simple as a loose access panel or a missing screw, while other times, it could mean damaged and out-of-place components inside your furnace. If you inspect your furnace exterior and don’t see any loose panels, place a service call to have an HVAC technician check your heating system for damage.

Tackle Furnace and Heating System Noises with Our Help!

Anytime you can’t spot the cause of a heating system noise, let us know. We are only a call away, and our team is available 24 hours a day, 7 days a week, and 365 days a year. From banging and squealing to rattling and whistling, we are committed to listening to your system and resolving its challenges. Contact our team here at Jarboe’s Plumbing, Heating & Cooling for help when you need it!

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