Furnaces can make a variety of sounds and noises; some may indicate that there is a problem that needs to be addressed. Some of the sounds you hear may be buzzing, humming, grinding, squealing or rattling. While hearing a noise may not necessarily mean there is a problem, you need to know what to be aware of so that you can decide whether to tackle the problem yourself or bring in a professional.
Rumbling – If your furnace rumbles after shutting down and it is an oil-burning hot water model, it could be that there is oil in the combustion chamber that has not burned. This is dangerous and could potentially produce carbon monoxide.
Buzzing – Some furnaces buzz after they shut off, which is pretty common. This may be taken care of by tightening the mounting of the transformer.
Squealing is another noise that some homeowners may notice if you have a forced-air furnace. Typically, a squealing noise indicates that the belt connecting the motor to the fan is slipping. Belts wear out and yours may simply need to be replaced.
Does your furnace make rattling noises? This may be solved by simply screwing the cover panels on tight. Rattling may also be caused when there is a crack in the heat exchanger; in this case, your unit should be checked at once due to the possibility of carbon monoxide coming through the ductwork.
A whining noise could indicate an air leak. If you hear a whining sound coming from near where your furnace is located, switch the furnace off and leave the blower only running. If the whining continues, remove the lower panel from the furnace and trip the power switch that runs the blower to see if the whining ceases.
Determining what is causing a whining sound can be a bit tricky, so you may want to have a professional check it out.
Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems). For more information about furnace noises and other HVAC topics, click here to download our free Home Comfort Resource guide.