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Jan 07

MM Comfort BLOG


Posted by MM Comfort BLOG

Tips to understanding what the sounds are your furnace makes and why

Furnaces are big metal contraptions with internal moving parts, so it’s not surprising to hear a few noises now and then when the heater turns on or off. Although most furnaces usually aren’t noisy, when it does make a sound we haven’t heard before, is it trying to get your attention?

Forced air furnaces are highly efficient heating systems that can quickly and evenly warm-up a house, but they also double as a central air conditioner in the summer. Due to the dual jobs they perform though, the many composite parts that make up these systems can cause noises throughout the house as heat travels up through the registers.

Typically, the majority of noises a furnace makes aren’t cause for alarm, but just to make sure, here are some of the sounds you may hear from your furnace and why:

  • If you hear a screeching noise coming from your furnace, it’s most likely a result of problems with a belt, bearing or the motor. While this isn’t hazardous, if left in poor condition, it can cause larger repairs later.
  • A chirping sound from your furnace mostly occurs when the unit has not been in use for a while and could just be an indication that the heat is coming on. After the furnace has warmed up and run for a few minutes, the noise may stop. If the noise continues or grows worse over time, it may need a belt replacement. In this case it’s probably a good idea to contact a furnace repair technician to check the unit and make any necessary repairs.
  • A rattling sound coming from the furnace could mean there is a panel loose and can be fixed by simply tightening the cover panels. If you have checked the panels to make sure everything is tightened, the rattling noise may be from your furnace expanding and contracting the metal parts as they heat up and cool down. However, if the rattling noises still continue it may be something more serious and a furnace repair technician should be contacted.
  • If a clanging or knocking noise occurs only when your furnace first starts or right after it stops blowing hot air, the sound probably is caused by expansion and contraction. The metal housing, vents, pipes and other parts make clanging and banging noises as they heat up and cool down. This is normal and shouldn’t indicate a problem.

A continuous knocking sound though that occurs while the furnace is running is a signal that a furnace repair technician should be contacted. The two most likely sources of the continuous sound are a damaged or cracked belt, or bad bearings.

  • A loud boom or bang coming from your furnace could be one of two things. If the boom or banging noise is located at the heater, a delayed gas ignition is most likely the problem. Delayed gas ignition is when gas in the furnace builds up rather than igniting immediately. When the gas finally ignites after a while, a mini explosion happens and can harm your furnace. 

The second cause of a loud boom or bang could be the metal ductwork that’s expanding and contracting when the heating system’s blower starts. Try changing the air filter and make sure your home’s supply vents are open. If that does not solve the problem, you’ll need to contact a professional to find a solution. 

  • If a humming sound is coming from the furnace, begin by trying to pinpoint where the hum is originating from. One of the most common problems is that the blower motor makes a humming sound. If this is the case, then the first thing you should do is turn off your motor and allow it to cool. When it has cooled down to a safe temperature, check the motor, the humming could be the result of something as simple as improper lubrication.

Once your house is warm, the furnace blower begins to naturally run on a slower speed. But if your blower motor slows down unusually and makes a humming sound when it has slowed down, it might be due to a fault in the capacitor and the motor and may have to be replaced. This problem is typically caused by dust and dirt in your filter. An unclean and blocked filter makes the motor work harder to push out air. Make sure you check and clean the filter regularly to avoid this kind of problem from recurring.

HVAC (heating, ventilation and air conditioning) systems require the expertise of a professional for proper installation, maintenance and repairs. If you are having problems with your furnace, it is important to remember to always contact a heating and air conditioning specialist.

By taking care of and properly maintaining your home’s HVAC unit, you’ll have an efficient heating and cooling system that will provide for your family’s comfort for many years to come.

Have questions about a strange or loud noise coming from your furnace? Contact MM Comfort throughout the Seattle area to help with your Heating and Cooling needs.

MM Comfort experts can help you with repairs and servicing of your current HVAC system or help you choose the best heating and cooling options for your home, no matter how big or small it may be. Call us at 425.881.7920, or use our online contact form to arrange for a free heating and cooling consultation