Have you noticed that your furnace has recently started running loudly or making odd sounds? Excessive and/or unusual noises indicate an issue with some part of the furnace. In this article, we’ll look at the most common furnace noises, what causes them, and how to fix the problem.
Booming Sound When Burners Light
You may hear a succession of different sounds from a gas furnace. The sound of startup can echo through your air ducts. You’ll first hear a reasonably quiet sound caused by the furnace’s inducer fan coming on. This fan creates negative air pressure to ensure that the hot combustion fumes are drawn up through the heat exchanger and then vented outside through the exhaust flue. Once the inducer fan is fully up and running, it triggers a component known as the pressure switch. This signals the gas valve to open so the electronic igniter lights the burners. Once the heat exchanger reaches a specific temperature, you’ll hear the blower come on.
You may hear a fairly loud noise just as the burners light. However, the furnace shouldn’t make an overly loud booming sound. If you hear this noise, it indicates a slight delay from when the gas valve opened until the gas was finally ignited. When this happens, the combustion chamber starts to fill with gas. The gas then produces a small fireball once it lights. If your furnace makes this noise, you should check it out as soon as possible.
This issue typically happens for one of two reasons. The burner assembly or gas ports near the electronic igniter may be partially or fully clogged. The electronic igniter can cause a delayed ignition. Furnaces either have a hot surface igniter or a direct spark igniter. If a hot surface igniter is still working, it will light the gas immediately. If you have a direct spark igniter that’s beginning to wear out, it may fail to spark immediately, leading to an ignition delay.
Metal-on-Metal Grinding Noises
The inducer fan and blower are the only two moving components in a furnace. That means if you hear a sound like metal grinding on metal, it almost certainly comes from one of these two parts. In most cases, this sound indicates that the blower has started to come loose, resulting in the blower wheel scraping against the housing. When facing this situation, shutting your heating system off is a good idea. If it keeps running, the blower will likely need to be replaced.
Squealing or Screeching
Squealing noises may indicate an issue with the bearings that drive the blower motor. If you have a much older furnace with a belt-drive motor, it may also mean the belt is worn out. If your furnace has a bearing-drive motor, the sound usually means the bearings are wearing out. If you hear noises like this, call a professional. Ignoring this issue will eventually cause the blower motor to wear out. Replacing or lubricating the bearings isn’t all that expensive, but replacing the blower motor can be quite costly.
Hissing and Whistling
Whistling and hissing are signs of gases moving through small openings. Like breath through a flute, a duct with holes can create musical tones as air flows through it. If you hear these sounds coming from ducts, stand near your furnace to see if you hear similar sounds. If your furnace sounds quiet, you may wish to call a professional to inspect your ductwork.
If you have a gas furnace, hissing may also be a sign of a natural gas or propane leak. Carbon monoxide detectors can help to detect fumes caused by combustion, but they can’t detect gas before it has been burned. Instead, a natural gas detector is required. Companies put a strong-smelling chemical into propane and natural gas to warn you of its presence. If you smell this, exit the house immediately with your family and pets, shut off the valve for the main gas or propane line to the house and call emergency services.
Rattling
Rattling most commonly comes from a loose component. This may be a piece of your furnace or your air ducts. This is another issue, so you should have a technician check immediately. It may be a sign that your gas furnace heat exchanger is cracked. A cracked heat exchanger is a severe problem, resulting in combustion fumes escaping and mixing with the hot air from the furnace. There’s a chance you can end up with carbon monoxide circulating throughout your house.
Loud Fan
If your heating system starts producing much more noise than it usually does, it could mean that the blower has to work extra hard for one reason or another. One possibility is that it’s beginning to fail due to its motor wearing out. It can also be that the housing is caked in dust, which also interferes with the blower’s ability to circulate air and results in it working harder. The most common reason that the blower will work harder and run louder is that the furnace filter is dirty. That’s why the first thing to do if you encounter this issue is to replace the filter, as it may fix the problem and save you from paying for a service call.
Other Noises
There are a number of outside factors that can also cause sound to emanate from your HVAC system. A leak in your roof can drip onto your ducts and create a tapping sound. Rodents in or on top of your ductwork can sound like scurrying and chewing. These noises may be obvious in some cases. However, when they are deep within your walls or ceiling, echoes and insulation can alter the sounds. One clue that you have an issue with your ductwork but not your HVAC unit is timing. If the sounds are not occurring when your furnace or air conditioner is running, the issue is probably in your ducts. While a ductwork expert may be able to help you diagnose the cause, you may need a different kind of expert to address the problem in these cases.
How Regular Maintenance Helps Prevent Furnace Issues
The best way to avoid all of the issues in this article and most other furnace problems is to have a professional HVAC technician service your furnace at the start of each winter. Servicing a furnace includes essential tasks like cleaning the burners and blower housing, testing the igniter, checking the safety switches and all other necessary components, etc. The technician will also lubricate all moving parts as needed and test that your furnace is functioning as well as it should. That way, your heating costs don’t increase and your unit stays reliable. Your furnace will usually have a longer lifespan if serviced yearly.
With over three decades of experience, Coleman Mitchell Heating & Air Conditioning is the company to count on when you need heating or air conditioning service in Bridgewater, PA. Our certified technicians can work on all makes and models of HVAC equipment and are ready to assist when you need repairs or maintenance. We’re also available 24/7, so you can call us whenever an emergency arises. We pride ourselves on being the top HVAC service in the area and will do whatever it takes to make sure your home stays sufficiently warm during the winter and cool enough during the summer.
To get to the bottom of your furnace issues, contact us today for a full inspection.
