Frightening Furnace Noises and What They Mean
Are menacing sounds coming from your attic or basement? Before you call in the paranormal investigators, do a little investigating of your own and find out if those terrifying noises are coming from your furnace and how to fix them.
Frightening Furnace Noises
If you are hearing strange sounds in the middle of the night, it's not necessarily a ghost or ghoul.
If you hear a loud boom coming from your furnace, it's likely that there is a delayed ignition problem and what you are hearing is a mini gas explosion.
This is very similar to what may happen when you leave the gas running in your outdoor grill and then decide to turn on the ignition switch. When gas builds up inside the container and the ignition switch is lit, you will experience a small to medium gas explosion.
Why is this happening to me? There are several reasons why your gas may have a delayed ignition, including a high air-to-gas ratio, not enough gas, low gas pressure, clogged burners, and dirty equipment.
If you haven't had your furnace maintained yet, now is the time to do so! When you schedule HVAC maintenance with Gold Medal Service, we make sure to inspect the entire system and clean and test all components.
We make sure the burners are clean and that you have a healthy blue pilot flame color. If your pilot flame is any other color than blue, call your HVAC technician come and take a look. This is a tell-tale sign that you have a problem with your furnace. We also work on heat pumps, boilers, and more.
If you hear a deep rumbling throughout the house when the furnace finishes one of its cycles, it could be due to oil that continues to burn in the combustion chamber even after the burners are off.
Rumbling sounds can indicate problems with your blower motor, burners, flame sensor, or pilot light.
Call a professional HVAC technician to inspect and tune-up your furnace. They will be able to tell you why you are experiencing a rumbling sound.
Popping and Banging
If you hear popping or banging metal noises, you could have a problem with the way your ductwork was installed.
Although all air ducts make some noise, sometimes what you are hearing is "oil-canning," which is when there is a significant pressure difference between the supply and return ducts. This will move the metal sheet walls in and out, causing a popping and/or banging sounds.
Some innocuous sounds, such as creaking and the sound of air flow is normal, but constant pops and bangs are something you want to bring up to your HVAC technician. Ask your technician first about the ductwork.
You don't want to start making adjustments and repairs if the entire duct system needs to be replaced. Just like HVAC units, ductwork installation is complicated and requires a lot of expertise. If the person who installed your ductwork wasn't experienced, you may be better off replacing the ductwork or opting for a ductless system (where you won't have to worry about any ducts at all!).
If the duct system is fine, but the noises are still annoying you, there are several things you can do for noise reduction. First, make sure that you have sealed your ductwork with mastic sealant or aluminum foil tape. Then you can insulate the ducts with fiberglass insulation.
If you are looking for a professional duct sealing solution, learn about Aeroseal Duct Sealing, which seals all of the cracks and gaps in your ductwork from the inside! Not only will this help reduce your energy bills, it will also minimize any noises produced.
The two main causes of a loud bang are:
- Contracting and Expanding Metal - most likely the contraction and expansion of metal will be coming from your ductwork, but can occur anywhere in the HVAC system. When you have ducts that are undersized, closed, flimsy, or have poor airflow, it's important to take a look at your duct system and have it repaired as soon as possible.
- Dirty Furnace Burners - dirt and debris on the burners and flame sensors can cause a buildup of gas, which when lit, will create a loud, reverberating bang.
Never ignore this sound as this could also indicate a cracked heat exchanger, which is notorious for leaking carbon monoxide into the home.
Although sometimes you can tell if you have a damaged heat exchanged by listening for rattling noises, many times a further investigation is needed. A cracked heat exchanger is something you want to pay attention to since it leads to carbon monoxide leaks that can cause sickness, and even death.
Make sure you have carbon monoxide detectors installed throughout the home and you are testing them (along with your smoke alarms) every 30 days!
If the CO detector near your furnace goes off, that is a strong indication that there is some kind of damage to your HVAC system.
Carbon monoxide is produced whenever any fuel is burned, so if a CO alarm goes off, it's probably coming from your furnace. If it's not your furnace, check inside and outside your home for any fuel-consumption happening.
Is a car running in the garage? Is someone grilling indoors? NEVER ignore a CO alarm!
Learn more about carbon monoxide safety.
Discolored and Erratic Furnace Flame
If you have a cracked heat exchanger, you may be able to tell by looking at your furnace flame. Look for a flame that moves erratically and jumps around. The pilot flame should be blue and fairly still.
A damaged heat exchanged normally produces flame problems.
Rattling and Scraping
If you are hearing metal against metal, it could be the blower fan coming loose and hitting another metal part inside, most likely the side of the housing. This could mean that the blower motor mount is broken or the blower has otherwise become displaced.
It could also be a screw or another piece of metal that fell into the blower wheel and is being kicked around.
In either case, turn off the unit immediately and call a professional for help before you cause any more damage. It may be as simple as tightening a few screws, or you might need a professional blower wheel replacement.
Screeching or Squealing
If the sound is coming from your furnace and not from a tormented soul, it's probably because a motor belt slipped off its track.
There are three main causes for a squealing sound:
- Loose Fitting and Fraying Blower Belts - don't try to adjust or replace your furnace blower belt on your own (this should always be performed by a qualified technician).
- Dry Shaft Bearings - can create a squealing sound. Call your HVAC technician to lubricate the shaft bearings and prevent the high-pitched squeal.
- Broken Blower Motor - when you motor ages, it develops problems that are easily detected by the sounds it makes. If it’s making a squealing sound, it's likely that you need a professional repair or replacement.
Cacophony of Clicks
A clicking sound is perfectly normal when you turn on the gas to your oven, gas grill, or furnace. It's similar to the sound you hear when you are using a lighter.
In order for heat to be produced, some sort of ignition has to light the fuel. Clicking sounds are perfectly normal unless the clicking is followed by more clicking and no ignition ever happens.
If you hear a clicking sound and the blower turns on and then off again, you probably have a problem with your flame sensor. Call you HVAC technician for a furnace inspection and cleaning.
Call a Heating Professional Every Fall!
Many things can go wrong with a furnace, including carbon monoxide poisoning, which can cause hallucinations and even death. The problems highlighted above are just a few examples of what could go wrong.
Avoid an real-life horror story in your home by remembering to schedule furnace maintenance every fall and air conditioning maintenance every spring. We recommend signing up for a Home Maintenance Plan so you never have to remember this important home maintenance chore again.
All of our electrical, plumbing, and HVAC work comes with 100% Satisfaction Guarantee.
Winterize NOW and SAVE!
Call the professionals at Gold Medal Service to fix all your heating problems and ward off energy waste with these energy efficiency tips from the U.S. Department of Energy: