What to Do If You Hear Strange Noises from Your Heating System

Heating units, including furnaces, heating pumps, and boilers, produce a humming sound during normal operation. But what is the best course of action when unusual noises persist? Sure, the sounds can be a nuisance, but it’s important to recognize the significance of their warning of a system malfunction. This blog will guide you through the various heating system noises, what to do about them, and the circumstances to schedule a professional heating repair.

Why Do Heating Systems Make Noises?

Find below the various unusual noises produced by home heating systems, and learn what each means:

» Banging Noise

Ignition delay is among the common causes of the banging noise when a gas furnace or boiler kicks in. The delay causes gas to build inside the combustion chamber, leading to explosive combustion when the system finally lights. These minor explosions can cause significant damage to your system, costing you a ton of money in HVAC repairs.

Common causes of ignition delay in heating systems include:

• Weak pilot flame
• Dirty or clogged burners
• Low gas pressure

Ignition issues normally require the intervention of a professional heating system repair expert. 

Another culprit for banging sounds is the expansion and contraction of the ductwork as it heats up or cools down during and after the furnace’s heating cycles. You do not have to fret over banging ductwork. But you can minimize the noise by replacing rectangular ducts with round alternatives or installing thicker ducts. 

In boiler systems, banging noises may emanate from limescale buildup in the unit’s heat exchanger or air trapped within the pipes.  

» Scraping Noises

Scraping or screeching noises occur when pieces of metal rub against each other, and that could be the situation in your furnace. The obvious culprit is a loose or broken blower wheel hitting against the furnace casing. 

Scraping noises are distracting, but more importantly, they indicate problems that could cause further wear and tear in your system. We recommend turning the furnace off and having a reputable HVAC repair technician diagnose the problem.

» Whistling

Furnace whistling indicates a blockage in airflow, the same way you contract your lip muscles to whistle. It could be a clogged filter or objects obstructing the ductwork or closed vents. Corrective measures include:

• Cleaning or replacing the air filter
• Cleaning the ducts
• Clearing the vents and dampers

Though rare, the noise could occur due to a size mismatch between your furnace and your home/ductwork. Such a situation requires professional intervention, which could include furnace replacement.

Related Article: How Often Do I Really Need to Change My Furnace Filter?

» Squealing Sound

If your furnace or heat pump makes a loud squealing noise, it might be loose or slipped fan belt. You can verify this by inspecting the blower compartment. As you tighten the belt, you can adjust the belt tension by adjusting the motor mounting bolts accordingly. 

A frayed and worn-out belt needs replacing. You can do this yourself or leave it to a technician. For DIY, you may need to take the old belt with you to the hardware to get a matching replacement.

» Rumbling

A gentle whoosh or roaring sound is typical when a furnace completes a cycle, but anything beyond that in the form of rumble signifies trouble. If the rumbling is thunderous and continues after the furnace switches off, the cause is likely the remnant oil or gas burning in the combustion chamber. 

Do not wait any longer when you detect this issue; the extra fuel can cause a dangerous buildup of carbon monoxide in your home. Turn the furnace off and call for professional assistance. 

» Heat Pump Vibrating

When your heat pump is functioning correctly, it should be about as loud as a dishwasher. However, an uneven surface can cause noisy vibrations. Use a rubber pad to create an even base for your unit. 

» Water Heater Noises

Boilers, furnaces, and heat pumps are not the sole sources of strange heating noises. Your water heater can be noisy too, and below are a few causes:

• Crackling: Though not a cause for concern, crackling in water heaters indicates condensation in the burner.
• Popping/knocking sounds: They indicate the accumulation of calcium and other mineral deposits in your water heater tank. The solution is as simple as flushing the equipment. 
• Sizzling: It signifies leaking water falling onto the burner. You may check for water puddles at the base of your heater.
• Hissing: High temperature causes pressure buildup in the water heater. The pressure strains the T & P valve, causing a hissing noise. 

How to Troubleshoot Heating System Noises

Knowing what sounds are normal for your heating system allows you to recognize when something is amiss. If you hear a low, gentle hum, your system is doing just fine. But if the furnace is suddenly making a new, unpleasant sound, see if you can figure out the problem.

Although professional HVAC repair will often suffice for most heating system noises, there are a few fixes you can perform yourself to silence your system. They include:

» Replace a Dirty Filter

The filter traps particles, such as pet dander and dust from the air entering your heating system and being distributed in your home. That ensures you breathe fresh and healthy air. However, the filter can get clogged with time, impeding airflow and straining your furnace. Whistling occurs when air struggles to penetrate a clogged filter.

At Conejo Valley Home Services, we recommend replacing the filter every season. You not only resolve furnace whistles but also spare yourself constant heating system repairs. 

Remember, HVAC filters come in various designs, sizes, and thicknesses. Pick the right size for your furnace—one that allows adequate airflow and yet filters out as many airborne contaminants as possible. 

» Seal Duct Gaps

Check your duct for openings if whistling noises persist after ensuring your filter is working fine. Ducts are also known to produce banging and rattling noises. 

Tighten any loose connection and seal the gaps with duct or foil tape. HVAC silicone sealant is costlier but certainly the most efficient way to seal ducts. 

» Inspect the Air Dampers

Air dampers are plates sitting over vents to control the direction of the airflow in your house. When open, they allow cool air or warm air to escape. When closed, they prevent air from escaping.

Dampers can be mechanical (controlled with a valve installed outside the ducts) or automatic (uses a motor to close the plates)

Closed dampers impede airflow, causing the furnace to whistle. You may only need to adjust the vents and dampers to the open position. 

» Heating System Maintenance

You may not think about your heating system much when it is working well, but it’s important to schedule annual maintenance and keep up with other regular checks to avoid problems down the road. That’s because some issues are less obvious than others, and early damage can lead to significant heating repair costs later on. 

During the heating system maintenance, expect a technician will perform a series of tests on critical components of your heating system, including airflow, heat exchanger, blower motor, control thermostat, gas valve(s), and pressure switch. They may also recommend repairing or replacing any component showing signs of wear or damage.

When to Call for Furnace Repair or Replacement

Some furnace noises should not worry you. If you hear air being sucked into a vent, or your furnace sounds like it is rattling, whistling, or humming, these are often minor issues you could resolve. But if you hear a loud bang, boom, rumbling, screeching, or persistent humming coming from your heating, be quick to schedule a professional HVAC repair service with a competent local contractor. Replacement becomes necessary if your unit is beyond its prime or completely broken.

Note: Besides strange noises, issues that may necessitate heating system repairs include:

• Unusually high electric bill
• Uneven heat distribution in your home
• Home feels cold despite cranking up the thermostat
• Furnace turns on and off frequently 

Talking of furnace replacement, experts at Conejo Valley Home Services ensure you get a system customized to lifestyle and budget. It’s just one example of our commitment to providing you with home comfort solutions that go beyond short-term needs. We even offer financing plans that can make it easier for you to afford extra features or future upgrades as technology improves over time—without having to break the bank.