Sounds You Don’t Want Your Furnace to Make

Whenever our household appliances make unfamiliar noises, it’s usually a cause for alarm. It’s of particular concern when that noise is coming from the furnace. Unfamiliar furnace sounds, smells or erratic operation should always be addressed as soon as possible.

Here are some furnace sounds to watch out for.

Banging

Often, banging sounds are associated with the expansion and contraction of the ducts as air travels through them under pressure. The expanding ducts may be hitting other structures, such as pipes or framing.

Acoustic liners can help muffle duct noise so that it’s less noticeable. If the noise (usually a loud boom or bang) is originating at the duct joint at the trunk and plenum, an expansion collar could be installed. For noises caused by contact between ducts and structures, place padding between the points of contact.

Vibrations, Rattling

Rattling and vibrations could be from loose ducts. Have your ductwork inspected and any loose segments fixed with metal tape and screws, or mastic sealant. Never use duct tape.

Exploding Noise

Called ignition roll-out, this noise is rare but alarming. It results from a burst of flame as the ignition turns on to light the burners, when the flame is bigger than it should be. Have an HVAC technician check it out.

Scraping Noise

A loud scraping, as of metal rubbing against metal, may mean the furnace’s blower wheel is broken. Turn off the unit and call a technician.

Loud Popping Noise

A loud pop when the burners ignite may mean the furnace burners are dirty, causing delayed ignition as the gas builds up. These explosions can crack the heat exchanger, so don’t ignore them.