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Furnace Noises and What They Mean

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Is it furnace noises or ghosts in your basement?  While we won’t discount the latter, let’s assume it’s just your furnace talking and telling you what it needs. Yeah, let’s go with that.

Your furnace is an important part of keeping your home warm in winter. When working at peak efficiency, it transforms cold air into warm air, keeping your home and your family cozy and comfortable. But as your furnace ages, it’s more likely to have broken parts or to lose some of its efficiency. When this happens, you may hear strange sounds ranging from dull rumblings to loud screeching and grinding.

While some of these noises may be normal, many point to problems that need immediate attention. So to avoid dressing in every sweater you own and draping yourself in multiple blankets, get to know the sounds your furnace should and shouldn’t be making. And maybe you can also avoid needing to cleanse the house with sage.

So, What Are Normal Furnace Noises?

It’s normal to hear a noise as your furnace starts, especially in old furnaces. This noise is usually associated with your furnace igniting and working correctly. An initial pop or click as the unit turns on is entirely normal.  The furnace should then settle into a dull hum as it kicks into gear.

Other common noises include a crackling as metal component cool after a heating cycle,

But an excessive amount of these noises, or louder, stranger noises could signal a problem.

Furnace Noises That May Mean Trouble

1. Rumbling

A rumbling sound from your oil furnace is usually caused by a dirty burner or a malfunctioning pilot light. If oil or dirt has built up around the burner, this can cause rumbling noises as it burns away. You may also hear rumbling if the pilot light is having difficulty staying lit. It’s best to contact a professional to clean the unit and test the pilot light and make any necessary repairs.

2. Rattling

A rattling sound coming from the furnace could simply mean there’s a loose access panel or door. If you can visually see the problem and easily tighten the door or screw, you may not need a service call. But if that doesn’t solve the problem, it could indicate a loose part internally. Furnaces are intricate mechanical devices with constantly moving parts. These parts can become loose over time. Turn off your furnace and contact a professional to help you tighten the loose parts.

In rare cases, rattling could mean there’s a crack in your heat exchanger. A malfunctioning heat exchanger can leak carbon monoxide into your home, making it dangerous. And as in any situation, if your carbon monoxide detector is going off, leave the house and only when you are safely away, call the fire department to help determine the source.

3. Clicking

When you fire your furnace up, it may make a clicking sound. This is normal.  However, if the clicking persists throughout the heating cycle, there’s a problem with your furnace.

Repeated clicking often means there’s a problem with the ignition system. If your furnace can’t ignite, it may produce a clicking sound as the igniter struggles to come on.

Ignition system problems are usually caused by issues like a dirty burner, a defective ignition board or valve, or a damaged flame sensor. Besides the ignition system issues above, compressor or control panel issues may also result in clicking sounds. Additionally, a faulty fan motor can cause clicking sounds. It’s best to contact a professional technician to inspect your furnace if it makes repeated clicking sounds.

4. Whistling

Dirty air filters that haven’t been replaced in a while are a common cause of a whistling sound in your furnace. When the filter is dirty or clogged, air whistles through the narrow openings. If your furnace filter is a disposable one, it’s time to replace the filter. For a reusable filter, take it out, clean it, replace it, and test see if the sound is gone. Cleaning of furnaces and air filters are a routine part of most annual tune ups so make sure you are up to date on your system’s maintenance schedule.

5. Knocking

When your oil furnace knocks, it’s not trying to get you to answer the basement door. The most common cause is air bubbles trapped in the lines. The solution is to “bleed the lines.” This involves draining the lines to remove the trapped air and should be done by a licensed professional.

6. Humming or Buzzing

A low humming noise isn’t necessarily a cause for alarm. Many furnaces produce a dull humming sound while running. But if your furnace produces a loud humming or buzzing sound, there could be an issue with the motor. There may also be something wrong with the fan. It can be something as simple as a loose screw, loose door, or improperly installed furnace filter. Regardless, it’s best to have a professional check it out.

7. Grinding and Scraping

Grinding noises coming from the direction of your oil furnace are never good news. In nearly every case, they indicate a part has worn out and needs repairs or a replacement. When you hear grinding, always shut down your furnace until a diagnosis can be made. A frequent cause of grinding sounds is worn-out bearings. Because of the location of these bearings, it is best to contact a professional to repair it.

Scraping noises may indicate an issue with the blower wheel. It may be broken and need replacement. Or it may have become loose. Turn your furnace off immediately and call a technician to inspect it. Left unattended, it can lead to considerable wear and tear on your system and cause more costly issues.

8. Banging and Popping

Banging and popping sounds are normal. Often, furnaces make these sounds as the ducts expand and contract. However, if the banging and popping sounds are exceptionally loud and frequent, it could signal a problem with your furnace. These sounds are also caused by dirty burners that delay ignition. If your furnace starts making loud banging and popping noises, don’t ignore the problem. It could crack the heat exchanger, which could lead to a carbon monoxide leak. While oil burning furnaces naturally produce less carbon monoxide than their natural gas counterparts. the build-up of soot and other residues can increase your risk of carbon-monoxide poisoning since build-ups prevent proper ventilation. Make sure you use CO detectors in the home. If you suspect a leak, open all doors and windows and call an HVAC professional immediately!

9. Squealing and Screeching

Screeching, squealing or whining can indicate a belt has been stripped or has slipped out of place. These types of sounds can also indicate a problem with the blower motor. A worn-out or damaged belt may need to be replaced before you can use your oil furnace safely again. In some cases, the issue can be resolved by adjusting the belt tension. With blower motor issues, it is always best to contact a technician.

What Should I Do If I Hear These Noises?

As mentioned, in some cases, furnace noises can be normal. But many of these noises can result in serious safety issues, such as carbon monoxide leaks, or broken parts that prevent your equipment from heating your heating your home properly. So if your heating equipment is making any noise in excess, or you just aren’t sure what the noise means, its best to contact a licensed, experienced HVAC technician, like Levco, to diagnose and repair the problem.

Call Levco for All Your HVAC Service Needs!

Whatever your service needs or what type of equipment you have in your home, Levco technicians are among the elite in the industry. Whether it’s an annual tune up or a fuel delivery, we’re ready to service or maintain your system for optimum performance. Give us a call at (203) 533-8249 or contact us today!

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