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Our Furnace Makes a Banging Noise When it Shuts Off – We Explain What’s Wrong

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It can be quite alarming to hear a furnace that makes a banging noise when it shuts off, so we decided to explain what possibly the cause. In some cases, you may be able to rectify what's wrong without even calling your plumber. Read on:

So, Why Does My Furnace Make a Loud Noise When It Turns Off?

Watch our video below as we think it will quickly explain what to do:

I've got a 10-year-old Rheem gas furnace. I had an HVAC technician out to do the regular cleaning and maintenance and he gave it a good bill of health. But, 2 weeks later I turn it on for the first time and every time it turns on or off, there is one loud snap.

If you are noticing a loud noise coming from your furnace when it turns off as in “furnace makes banging noise when it shuts off” could be something very simple. The noise may be described as a loud boom or bang and can be disconcerting when you hear it, especially for the first time.

Text in image: "Furnace makes banging noise when it shuts off".

Recently my furnace starting making a loud “boom” sound at the end of a heating cycle. It's a relatively new furnace, and this is the first sign of any trouble I've had with it. I turned to Google and learned that a common source of that kind of noise is an incorrectly closed baffle or a dirty filter.

Your heating system becomes dirty as time passes, so that’s why it’s critical to set seasonal furnace maintenance. One of the jobs our technicians perform during this appointment is to clean your furnace’s burners, and quotebeating glasgow south side.

Your ductwork is https://www.quotebeating.co.uk/sensitive to temperature changes, and expands and contracts when the system turns on and off. If you hear loud noises, try opening up a damper to see if that improves the airflow in your ductwork and gets rid of some of the noise.

Your heating system turns grimy over the years, so that’s why it’s critical to set routine furnace maintenance with clean air HVAC. One of the jobs our professionals do during this service is to clean your furnace’s burners. When this component gets grubby, you might hear your furnace making a loud rumbling noise if the ignition is delayed.

If you are having problems with your furnace making a loud noise when it turns off, contact the furnace repair experts at one of the leading heating and cooling companies in your area.

Why Causes a Loud Noise When it Starts?

If your furnace is making a loud noise just as it starts, this could be caused by a serious problem called “delayed ignition. ” this occurs when unburned oil builds up in the firebox chamber and is ignited all at once.

Your heating system turns filthy as time passes, so that’s why it’s critical to schedule annual furnace maintenance. One of the tasks our technicians do during this appointment is to clean your furnace’s burners.

Your furnace uses ductwork to deliver hot air around your house. If the ductwork wasn’t installed correctly or is getting dated, it can be loud when your furnace is on. This may be the case if your furnace makes a banging noise when it shuts off.

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. Your heater may be trying to get your attention with unfamiliar noises.

Your heating system gets dirty as time passes, so that’s why it’s important to book annual furnace maintenance. One of the tasks the pros complete during this work is to clean your furnace’s burners.

Reasons Your Furnace Is Making Loud Noises

A common complaint is that their furnace is making a loud or strange sound they have not heard before. Here are some of the reasons your furnace could be making a funny noise.

Life is only comfortable as long as everything works, and everything works precisely as it should. Your AC system may be working as you expect it to, but you’ve started to notice that whenever you shut it down or start it up, it makes a loud noise.

Noisy pipes or ducts are an unwelcome distraction. However, it can be hard to locate the source of the problem. To help, we're featuring our top reasons why your pipes or ducts might be making noise one more time. Once you locate the source of the problem, it's time to make the fix.

When your furnace is functioning properly, it will not make clunking or knocking noises. One of the reasons a furnace could be making a knocking noise is an issue with the fan. For example, if the blower fan becomes misaligned, the blades can hit the walls or other parts of the furnace.

When furnaces begin making certain noises, it often means that something isn’t working properly and you should take action to get it fixed right away. There are many reasons this could be happening, so you’ll need to pay close attention to the type of noise your furnace is making so that you can better diagnose the problem.

Why Does My Furnace Make a Loud Boom When it Turns On?

All heating systems pick up dirt over time, so that’s why it’s important to schedule yearly furnace maintenance. One of the things our technicians perform during this service is to clean your furnace’s burning chamber. When this part gets dirty, you might hear your furnace making a loud rumbling noise if ignition takes longer than normal.

Is a loud furnace dangerous?

What’s that noise?! is it banging, rapping, scraping or screeching? whether the sounds are soft or loud, it’s enough to give anyone the heebie-jeebies. You’ll want to investigate. It is the beginning of the dark, cold winter after all.

A loud boom is a dangerous sound. It means your furnace has a delayed gas ignition. When this happens, the gas in your furnace builds up instead of igniting right away. When the gas does ignite, it creates a small explosion.

Can a furnace explode?

On very rare occasions a furnace can explode, and neglect to attend to warning noises can be the cause.

A gas-fired forced-air furnace system usually runs very quietly. Loud noises must be corrected by an expert, and in many countries that expert must be fully trained and registered with the relevant professional bodies. If all else is quiet, you can hear the blower running, but that's about all. If there's rattling or squeaking from here, call a repair service, as there is something not right with the motor or fan.

How do you know if your furnace is dying?

Some furnace noises are signs of major heating system malfunctions or indicate your furnace is dying. Trained local plumbing tradesmen provide annual servicing. This includes performing a thorough inspection of your furnace’s condition to provide you with a clear picture of any problem and the solutions available.

A common cause of buzzing in a furnace is a loosely mounted transformer box. Your furnace has a transformer that changes the incoming power to the voltage required for the furnace. The transformer is a small box inside the furnace that has wire connections on both sides.

Is it normal for a furnace to make noise?

Furnaces are known for their strange noises. Normal sounds you may hear are tiny little pops or hums as the furnace runs. However, when your furnace is noisier than usual or you start hearing a noise you have never heard before, this usually indicates that there is something wrong with your furnace and it may be time to talk to your heating technician about some maintenance and repairs.

The blower of my furnace makes a loud noise every time it starts. I understand that a large fan and the movement of large amounts of air will produce some noise. What one owner was puzzled by was a noise that sounds like a “starter”.

All noises such as nocking, banging and clanking noises are not normal for most appliances, but furnaces can be an exception. Loud sounds are not necessarily a problem unless they are coming from the motor.

All HVAC systems, to a degree, make noise while operating. However, how do you know if these noises are normal or an indicator that something is wrong? If you’re hearing strange furnace sounds or experiencing noisy furnace ducts, it could be either business as usual or a sign of trouble.

Why does my AC make a loud noise when it turns on?

The return grille is the opening where warm air from your home enters the ac to be cooled. Before the air reaches the actual ac system, it passes through a filter to remove dust and other contaminants. Return grille located on the ceiling in some homes, the return grille (vent) is located on the ceiling.

If you just bought a house and it's been very cold, meaning that you've had the heat running and when the heat turns on/off the ductwork in the house starts popping get a plumber to check it over as soon as possible.

Heating systems are not unique in making these loud noises in our house a 9-year-old freezer top refrigerator model no 106. 70204990 started making a noise. Every time the compressor turns off, a loud bang occurs. And this happens every 12 minutes. The compressor is on for 6 minutes then off for 6 minutes. If this happens, get an HVAC engineer in or replace the noisy compressor.

How often should you change your furnace filter?

Dirty furnace filters should be checked annually during servicing and how often they need replacing varies.  Some can often be washed out under the tap, others will need changing but generally, each filter should last for at least two years. This buildup gets more severe when your furnace filter is dirty and/ or you skip annual tune-ups for your system.

Regardless of the cause, dirt buildup on your burners will delay the ignition of the gas that is fed to your system.

Dirt in the furnace burners impedes the burners from igniting, causing gas to build up. As soon as the gas finally ignites, you will hear a loud bang. These small explosions could crack the heat exchanger, which is a costly repair.

Generally, a strong smell from your furnace is an indication that it needs to be serviced. Many furnace breakdowns are due to dirt or dust in the system so it’s important to get a tune-up at least once a year.

A whistling sound may be the result of a clogged or dirty air filter. Restricted airflow to your furnace can cause a whistling sound. In a dusty environment, a furnace filter may need changing as often as every 1-3 months to increase airflow, improve indoor air quality, and stop that whistling sound!

Gas (the most common), oil, and electric furnaces all have similar parts, including:

  • a burner (gas or oil) or heating element (electric)
  • a blower,
  • a heat exchanger,
  • a filter,
  • a plenum, and
  • various other parts.

Europeans tend to refer to a furnace as a boiler. Don't be confused by this as just like a furnace, a boiler heats your house.

The room temperature must drop a degree or 2 maybe 3 before a boiler/ furnace normally kicks on again.

Banging noise when a furnace turns off

Your furnace works with ductwork to deliver heated air around your house. If the ductwork wasn’t installed properly or is getting old, it can make a lot of noise when your furnace is heating. This can be a problem if your furnace makes a banging noise when it shuts off.

One of the most common causes of banging furnace ductwork is simply the expansion and contraction of the furnace and air duct system. When the system turns on and off, the ducts may expand or contract from the change in temperature and you may hear small and large banging noises.

The compressor is the part of your outdoor HVAC unit that pumps refrigerant to and from your indoor unit. And inside the sealed compressor casing are many parts, including the refrigerant pump. Most of these pumps are mounted on support springs.

Your furnace relies on ductwork to provide hot air across your house. If the ductwork wasn’t installed right or is ageing, it can be noisy when your furnace is on. This can be the case if your furnace makes a banging noise when it shuts off.

The metal ductwork in the ceiling of our finished basement pops and bangs every time the furnace comes on in the winter then makes more noise after the furnace shuts off. Is there anything we can do to stop the banging? Check that the filter is not blocked up from accumulating dust and if it is, change it for a new one, or wash the original, and return that one to use.

If you hear popping sounds and you don’t have a bag of popcorn in the microwave, you could be dealing with dirty furnace burners or damaged air ducts. When the burners are dirty, the buildup prevents them from igniting, which causes too much gas to build up, making a popping sound.

Furnace Noises You Should Never Ignore

If you hear a rattling noise coming from an exterior AC unit it could be because something fell into the vents such as leaves sticks or other outdoor debris. It is always worth checking this one out, as it can avoid calling out your local plumber or HVAC expert.

Loud Pop or Bang May be Due to Differences in Pressure Between the Supply and Return Ducts.

One of the main causes for these loud noises are differences in pressure between the supply and return ducts. Another common cause is expansion and contraction due to changes in temperature. Oil canning – when the walls of your air ducts move in and out due to pressure differences, you may hear a rumbling, popping sound.

The night before last, we heard a giant bang during our heat cycle. We have forced air heat. Our furnace has always occasionally had a small bang as it turned off, but this was mid-cycle and loud. Scary.

You turn on the thermostat, and after a minute, you hear a “bang” or a popping noise before the fan actually turns on. No matter what you read online, that banging noise is not something to take lightly! true, you probably don’t have to worry about the furnace exploding or catching fire.

Does your furnace remind you every time it's running by offering you a “bang” or a “squeaky, squeaky, squeaky” noise? sure, we are glad the furnace is on, but who wants the life scared out of them or to have to turn the volume up on the tv to mega-loud?

More often than not, noises from a furnace and ductwork are simple to fix and can be remedied rather easily with household items or small purchases of, for example, a new filter unit, from the local home improvement store.

Odd sound after furnace turns off after my furnace turns off (the very second) it makes this “creak” or low vibrato deflating kind of sound. This could mean your furnace has dirty burners. Call your local plumber in to solve this problem.

Why Does My AC Make a Slamming Noise When Shutting Off

Air conditioners and heat pumps are known to make loud noises when starting and shutting off. The sounds are described as the AC making slamming noises, AC making banging noises and it may also be described as the air conditioner making thumping noises at the start or stop

Why the ac makes a loud noise at the start or stop is not clear, but causes can be:

  • the air filter is loose, dirty or too restrictive
  • the blower motor or fan is broken or needs to be balanced
  • ductwork dampers are opening or closing
  • duct sheet metal is contracting or expanding with temperature changes.

If your furnace is making a rattling noise, it could be the result of something small, like an unsecured screw, or something critical, like a broken piece. In either case, we advise shutting your furnace off and calling out heating professionals.

The noise comes firstly from the recording environment and secondly from its immediate surroundings. Unless you're in a completely soundproofed room, which I'm guessing you're not, there will always be some noise, perhaps birds twittering outside your window, your fridge rumbling or your furnace growling.

If your furnace is making a rattling noise, it could be related to something little, like an unfastened screw, or something serious, like a broken part. In either case, we advise shutting your furnace off and calling our heating professionals.

Indoor Noise with Easy Fix

What causes that loud banging noise every time your AC comes on? fortunately, as bad as it sounds, it’s probably only a loose or broken (but non-essential) part. In most cases, it’s a simple fix. The parts that are usually responsible for banging noises during operation are a loose fan, a broken connecting rod, or an unbalanced indoor blower.

Outdoor Noise that’s Normal

Start-up troubles and loud continuous squealing was the problem for one gentleman, clanking, and what I take to be some humming at the outdoor fan-compressor unit contributed. The unit is now unable to start and run normally.

Many water heaters have heat traps or check valves installed in the pipes on top of the heater. These traps are designed to prevent water from flowing in the wrong direction in the pipes, and may make ticking or light tapping sounds.

Furnaces can make all kinds of noises that you might describe as clicking, popping, or knocking. Some other common problems include:

Furnace motor clicking? If the furnace makes a clicking sound while it operates normally otherwise, you might be hearing motor bearings or other small parts knocking around.

When your furnace is running as it should, it should give heat without creating too much disruption through its noise. While it’s normal to hear your furnace making noise as it starts up, other sounds are a signal you must not neglect. Your furnace should be given immediate professional assistance at the next opportunity.

Our new home is now 3 years old. Ever since move-in day, there have been annoying ticking noises in several interior walls of our home. Some of the noises start minutes after our furnace comes on. Your heating system becomes dirty over time, so that’s why you need to clean it.

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  1. Reply

    Thanks for pointing out that you shouldn’t leave a noisy furnace alone since they’re signs that it needs servicing. I have a friend who’s experiencing this on their unit and it also fails to warm their bedroom. He should probably look around for experts that can diagnose and fix this for him.

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