A Complete Guide to Furnace Maintenance

As summer starts to wind down and the kids return to school, it’s a clear signal that the heating season is just around the corner. While the temperatures may still be warm, it’s never too early to prepare your home for cold weather. Making sure your furnace is in good condition before the chill sets in can keep your home warm, your energy bills manageable, and your family safe this winter.

Regular furnace maintenance isn’t just a task for the pros – there’s plenty homeowners can do to keep their systems running smoothly and efficiently. By taking the right steps, you can extend the life of your furnace, improve energy efficiency, and prevent unexpected breakdowns when you need heat the most.

HVAC.com helps you navigate the essential tasks you can tackle on your own, as well as what’s included in a professional maintenance visit from your local HVAC technician.

Furnace Maintenance Steps for Homeowners

1. Replace or Clean the Air Filter

One of the simplest and most effective – yet often overlooked – maintenance tasks is replacing or cleaning your furnace’s air filter. A dirty filter can restrict airflow, which makes your furnace work harder and less efficiently. This can lead to higher energy bills and even system damage.

How to Do It:

• Locate the filter, usually found inside the blower compartment or behind a removable panel.
• If it’s disposable, replace it with a new one of the same size and type. Make sure to insert the new filter in the correct direction, following the arrows printed along its frame.
• If it’s a reusable filter, follow the manufacturer’s instructions for cleaning, which often involves rinsing it under water and letting it dry completely before reinserting.
• Check your filter monthly once the heating season starts, as filters often require more frequent care during periods of heavy HVAC system use. Replace or clean it every 1-3 months.

2. Check and Clean Vents and Registers

Blocked or dirty air vents can impede the flow of warm air throughout your home, forcing your furnace to work harder and creating hot and cold spots across your home. Dirty vents and registers can also cause more dust and debris to circulate, worsening indoor air quality.

How to Do It:

• Walk through your home and locate all vents and registers.
• Make sure they’re not blocked by furniture, rugs, or curtains.
• If you have louvered vent covers, check that all the louvers are fully open. If the louvers are stuck or broken, replace these covers.
• Use a vacuum with a brush attachment to clean dust and debris from the vent openings.

3. Inspect the Furnace Area

Keep the area around your furnace clear to ensure proper airflow and prevent fire hazards. Regularly check this space for obstructions or issues.

How to Do It:

• Clear away any clutter – including boxes, laundry, or other items – from around the furnace.
• Make sure there’s at least three feet of clearance on all sides.
• Do not store combustible materials near the furnace.
• Check for any signs of leaks or rust on the furnace itself, which could indicate a problem that needs professional attention.

4. Furnace Humidifier Maintenance

If you have a whole home humidifier with your HVAC system, it also requires maintenance to ensure it provides the moisture needed to combat dry winter air.

How to Do It:

• Locate the humidifier, which is usually installed directly onto the return duct, supply duct, or on a bypass duct to the furnace. Turn off power to the humidifier before starting maintenance.
• Clean or replace the humidifier pad.
• Check that the water supply line to the humidifier is clear and open. Then, look for any signs of leaks, blockages, or wear, and make sure the valve is functioning properly.
• If your unit has a water reservoir or other components that can collect sediment, give them a good cleaning to remove any scale or buildup. 

5. Replace Batteries in Smoke and Carbon Monoxide Detectors

Gas furnaces burn fuel to generate heat, which can produce carbon monoxide – a colorless, odorless gas that’s dangerous if it leaks into your home. Smoke and carbon monoxide detectors are necessary safety devices that can alert you and your loved ones to the presence of these threats, so make sure they are working properly.

How to Do It:

• Check if your detectors need replacing, as most have a lifespan of 5 to 10 years. Look at the label on the back of each unit for the manufacturing date or an expiration date. If your detectors are expired, make sure to replace them.
• Test each detector in your home to make sure it’s working.
• Replace the batteries, even if they’re not dead. If your detectors are hardwired, you should still make sure each unit has fresh batteries as a backup in case of a power outage.

Schedule Professional Furnace Maintenance

While there’s plenty homeowners can do to maintain their furnaces, a professional inspection and tune-up is incredibly valuable. HVAC technicians can identify and address potential issues that might not be visible to you, and ensure all parts of your system are working properly and efficiently.

Here’s a look at what happens during a professional furnace tune-up:

Inspecting the Furnace

The technician begins with a detailed inspection of your furnace. This includes checking all internal and external components for signs of wear, damage, or potential issues. Key areas of focus include:

• Heat Exchanger: The technician will inspect the heat exchanger for cracks or damage. A cracked heat exchanger can leak carbon monoxide into your home.
• Burners: The burners are examined to ensure they are clean and operating properly. Dirty burners can cause incomplete combustion, leading to poor efficiency and potential safety hazards.
• Ignition System: Whether your furnace has a pilot light or electronic ignition, the technician will check that it’s functioning correctly to ensure reliable operation.

Cleaning Critical Components

Over time, dust, dirt, and debris can accumulate in your furnace, affecting its performance and efficiency. The technician will clean several critical components, including:

• Burners: Any buildup on the burners is removed to ensure proper combustion and efficiency.
• Blower Motor and Fan: Dust and debris are cleared from the blower motor and fan to improve airflow and prevent overheating.
• Flame Sensor: The flame sensor is cleaned to ensure it can accurately detect the burner flame.

Checking Electrical Connections

Loose or corroded electrical connections can lead to system failures or even pose a fire hazard. The technician will:

• Tighten and Secure Connections: All electrical connections are checked for security, and any loose connections are tightened.
• Inspect Wiring: The technician looks for signs of wear or damage to the wiring that could cause shorts or failures.
• Test Safety Controls: Safety controls, such as limit switches and sensors, are tested to verify they will operate correctly if the furnace overheats, or another issue arises.

Lubricating Moving Parts

Furnaces have several moving parts, such as the blower motor and bearings, that need to be properly lubricated to reduce friction and prevent wear. The technician will apply lubrication where needed to keep these components operating smoothly and quietly.

Testing System Performance

To ensure your furnace is running efficiently and effectively, the technician will perform several performance tests, including:

• Thermostat Calibration: The thermostat is checked and calibrated to ensure it accurately reflects the temperature and controls the furnace correctly.
• Airflow Check: The technician measures airflow to confirm that the system is delivering the proper amount of air throughout your home.
• Carbon Monoxide Test: A carbon monoxide test is conducted to ensure that the furnace is burning fuel cleanly and that there are no dangerous leaks.
• Fuel-to-Air Ratio Check: The balance between the amount of fuel and air being mixed and burned in the furnace is measured and adjusted if needed to maximize efficiency.

A professional furnace tune-up is a comprehensive service that goes beyond what most homeowners can do themselves. With annual maintenance from an HVAC technician, you’ll ensure your furnace runs efficiently, safely, and reliably throughout the heating season. This preventative care helps extend your furnace’s lifespan, boosts indoor comfort, and can save you money on energy bills.

How Often Should Furnace Maintenance Be Performed?

Furnace maintenance should be performed at least once a year to ensure optimal performance and prevent potential issues. Scheduling a tune-up before the heating season starts – typically in the fall – can help catch any problems early and keep your system running smoothly throughout the winter.