Many households stay warm during wintertime with a furnace. Modern furnaces are very safe and should be virtually silent when functioning well. Find out more about the noises you may hear that can indicate potentially serious problems.
A Bang or Boom Upon Startup
Fuel-burning furnaces are prone to dirty burners due to carbon deposits from combustion. Gas can build up because of the blockages and lead to delayed ignition. When the built-up gas finally ignites, it essentially creates a small explosion and the boom sound. The danger is that repeated booming can eventually crack or otherwise damage the heat exchanger. Another risk is that dirty combustion equipment increases the likelihood of carbon monoxide (CO) exposure.
High-Pitched Squealing or Screeching
These sounds are often the result of a blower problem. They can be loudest when the furnace first turns on but will often continue throughout the cycle. With most modern blower motors, this noise indicates that one or more worn ball bearings require replacement. With some older configurations, it can mean you have a frayed or otherwise worn blower belt. It may also suggest that the blower motor lubricant has dried out. A prompt response will generally lead to a relatively inexpensive repair. If you delay service, the extra friction can eventually cause significant blower damage requiring expensive repairs.
Whistling From Your HVAC Return
All central HVAC systems have one or more returns where air enters the system. The returns require filters to improve air quality and protect the HVAC equipment. A whistling sound means that the filter is clogged, and the air is now circumventing it. Replacing the filter will solve the problem. Continuing to use it as is will cause excessive static air pressure. That will diminish energy efficiency and could eventually cause damage to the HVAC components.
Persistent Clicking
You may hear an occasional click from your furnace, especially when the furnace cycles on. That usually isn’t cause for concern since some components will click when they activate. If you hear persistent clicking, it often suggests a failing ignition system or a faulty flame sensor. If the system clicks but fails to turn on, stop using the furnace until a professional can inspect it. With both electric and fuel furnaces, it may be the result of an electrical short in the control board. With fuel furnaces, there’s also the risk of unburned gas dumping into the combustion chamber.
Rattling or Other Rumbling
There are many potential furnace issues that can result in rattling or other vibrations. Sometimes, the problem can be as simple as a loose screw or an access panel. If the sound is from the ducts, it could be failed mounting hardware rather than an issue with the furnace itself. If the vibration is coming from the heat exchanger, then the underlying problem may be quite serious. If you notice the pilot light flickering or not burning blue, stop using the furnace immediately. Those are telltale signs of CO exposure.
Whistling or Hissing
A hissing or whistling sound is usually an indication of an airflow obstruction. Earlier, we discussed clogged return filters. Some furnaces have filters directly within the unit itself. It could also be an obstruction within the ductwork. Ducts can accumulate dust over the years that can eventually get dense enough to block air. There may be one or more blocked vents throughout the home. You may also have duct leakage that requires duct sealing or other duct repairs.
Grinding
Grinding is usually blower related and may occur intermittently or on a recurring basis. One potential cause is that the blower fans are imbalanced and require rebalancing. There could be a foreign object in the assembly causing the interference. It could also be some of the issues discussed earlier regarding squealing and screeching. Those include a lack of lubrication, worn ball bearings, or a worn blower motor belt.
Humming That’s Louder Than Usual
Furnaces do create some sound, and it should be relatively steady during a cycle. With modern furnaces, it’s generally low enough that most people don’t notice it at all. If you do hear or feel it, it should be nothing more than a light hum. If it intensifies, then it could point to a problem with the furnace’s electrical system. Possibilities include coil whine, bad capacitors, worn electrical wires, or loose connections.
CO Detector Chirping or Alarm
Homes with fuel-fired furnaces need adequate CO detector coverage. An unexplained activation may indicate the furnace is releasing CO into your living spaces. It’s also important not to ignore intermittent chirping. It may mean that the CO detectors are not providing active monitoring.
Your Local Furnace Experts in Southwest Florida
Arctic Air Home Services services electric and fuel-fired furnaces out of our location in Sarasota, FL. Our technicians provide inspection and seasonal maintenance services. We also perform both warranty and non-covered repairs for all furnace brands and models. To schedule an appointment, call today or book online through our website.
