When Your Heating System Makes Noise as It Runs, Here’s How You Can Fix It

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

Any odd noise coming from a furnace, boiler, or heat pump could mean something in the system has malfunctioned and is in need of repair. While low humming sound is typical when heating systems operate, any sound that is not common coming from the furnace or heat pump could mean a problem is present.

Whether it’s a banging noise, rattling, whistling, or something else, Williams Comfort Air is here to help. Below, find out what might cause the loud sounds you notice in your home and what these noises could mean for your HVAC system. Make sure you don’t ignore an unusual noise coming from the furnace or heating system, because any new noises are a sign your furnace, boiler, or heat pump is trying to tell you something. Parts might need to be replaced by a professional technician or your system may need service.

Why Do Heating Systems Make Noises?

Noises from heating systems that are not the usual humming sound typically mean there is something wrong, whether it’s malfunctioning parts inside the furnace, a simple error that you can fix on your own, or something more serious that requires professional service help to correct. Learn what that sound coming from your heating and air conditioning system means and what you need to do about it.

Banging Noise

Banging noise from a furnace, boiler, or heat pump can mean a number of things. Here are some of the potential problems this loud noise indicates.

Ignition Issues

When your gas furnace or gas boiler system makes a banging noise as it starts up, an ignition issue is likely. A problem with the ignition parts prevent the burner from igniting when it should and can cause a buildup of gas inside the system’s combustion chamber. Once the heating unit finally lights, this excess gas is ignited, causing a loud banging noise. The ignition system will need repair to prevent this potentially dangerous issue. Burner cleaning may be needed if they are clogged, or the gas pressure or pilot light flame may be too weak.

Air Inside Pipes

If you have a boiler heating system, trapped air within the pipes can cause a loud banging noise throughout your home. To rid the system of trapped air, you need to bleed the pipes.

  1. Shut down power to your boiler system.
  2. Find the valve below the radiator end cap and turn it counterclockwise to release air pressure.
  3. Once air escapes the pipes and there is a trickle of water coming from the valve, close it.
  4. Repeat this step for all radiators in your home.

*Note: If you are uncomfortable doing this yourself, contact your HVAC technician to bleed your pipes and fix the issue.

Buildup on Heat Exchanger

A banging noise from a boiler can also mean there is a buildup of limescale on the unit’s heat exchanger. Professional service will be necessary to clean out the system and protect the heat exchanger. The boiler may make a whistling noise, called kettling, when this problem is present. The whistling mimics the hot, boiling water inside a teapot.

Ductwork Expansion

A banging noise can also be caused by the ducts throughout your home as the furnace, boiler, or heat pump runs. When heat hits the cold metal ducts, it causes expansion. When the heat cycle finishes, the ducts start to contract which may produce a loud bang. While these noises from your ductwork can sound concerning, there’s usually nothing wrong with your ducts or ductwork system – it’s just a normal sound.

Grinding Sound

A grinding noise from your system’s blower fan typically means the bearings in the motor do not have enough lubrication. As the furnace or heat pump runs, the bearings cause a grinding sound. This is common if the heating system has not had its regular maintenance tune up, as the blower motor bearings are lubricated during this service. Schedule a tune up if you haven’t already this year to make sure the motor and blower are not damaged during operation.

Squealing Sound

If you hear a squealing sound from your furnace or heat pump, it’s a good idea to check the fan belt within the blower compartment. A loose or slipped belt is usually the cause of this problem. The blower motor and fan in your unit may be linked by a belt, which can break or slack.

  1. Turn off power to your heating system.
  2. Open the panel to the blower compartment so you can see the fan belt and motor.
  3. Check for signs of fraying and wear – a damaged fan belt needs to be replaced.
  4. If the belt is loose, it needs to be tightened – there shouldn’t be more than a half inch of give in either direction. If the tension is loose, tighten it by turning the bolt on the blower motor.

If your blower motor fan belt needs to be replaced, you can do so yourself or contact a technician to make this repair for you. If you want to make the repair yourself, take the old belt with you when you purchase a new one to make sure you buy the correct parts.

Rattling Noises

Rattling noises from the heating system tells you something is loose. Usually, it’s a panel on the exterior of the furnace or air handler, but it could be loose parts within the unit. Inspect the panels on your heating system and make sure each fits securely while the system runs. If you do not notice any loose panels, rattling sounds are usually due to loose parts inside the system and a professional will need to make a repair.

Furnace and Heating System Noises Are No Problem with the Right Help!

If you are unable to diagnose the cause of the heating system noises you hear inside your home, call a professional for help. Service will find the cause and fix parts to prevent something like this from happening further. Whether it’s a banging, rattling, squealing, or whistling noise you hear, contact Williams Comfort Air for fast repair service for your furnace, heat pump, or boiler heating system.

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