Can It Get Too Cold for My Furnace?

As polar vortices become more common, you may wonder if it can get too cold for your furnace. In cold weather, the furnace works harder to overcome the temperature difference between the indoor and outdoor air. If your furnace is undersized, it may not have the capacity to heat your home properly, and freezing weather can cause other problems that affect furnace operation.

This May Also Interest You: The 4 Types of Furnaces

Can the Weather Outside Ever Get Too Cold for My Furnace to Function Properly?

Yes, it can get too cold in winter for your furnace to work correctly. Common furnace issues in cold weather include:

• Insufficient design capacity. When the weather is colder than the furnace's design capacity, it may not heat your home sufficiently.

• Equipment failure due to frigid temperatures. Extremely cold weather, ice and snow can cause components to malfunction, shutting down the furnace.

• Continuously running fan. If the fan runs all the time, it will blow cold air during the furnace's off cycle, causing unpleasant temperature variations in the home.

What Can Happen If My Furnace Can't Keep Up With the Cold?

When the weather is extremely cold, your furnace has to work harder, which can affect its performance and efficiency. Other factors can also reduce your furnace's effectiveness:

Furnace Isn't Sized Correctly

If your furnace doesn't have the right capacity to match the size of your home, it can struggle to put out sufficient heat and may run constantly — something it's not designed to do — which could lead to component breakdowns.

More Related Articles:

• Need a New Furnace? Here’s What You Should Know About Costs

• How Much Does It Cost to Switch to an Electric Furnace?

• Do You Need a Zoned HVAC System?

• How Much Does It Cost to Replace an Oil Furnace?

• Why Doesn't My House Have HVAC Return Vents?

Thermostat Isn’t Functioning Properly

If the thermostat is in the wrong location, it may be switching the furnace off too soon to heat your home properly. Alternatively, its calibration could be out, or it may have an intermittent fault. The cause might be as simple as a dead battery.

Too Much Heat Is Getting Lost

The furnace may be working correctly, but you're losing too much heat. Causes of excessive heat loss include:

• Leaking ducts. Damaged ducts can leak warm air into wall cavities or other unfinished areas, preventing enough heat from reaching the rooms in your home.

• Poorly sealed doors and windows. Drafts from poorly sealed openings may overwhelm the furnace.

• Insufficient duct insulation. Hot air loses warmth as it passes through uninsulated ductwork in unheated crawlspaces and attics, resulting in poor heating of your home.

Airflow Is Restricted

Insufficient airflow is another common cause of poor heating in winter and may be due to:

• Clogged air filter. A dirty filter restricts airflow and may cause the fan to pull cold air into the return air box.

• Blocked ducts. Blocked or kinked ducts can restrict airflow and cause poor heating.

• Faulty blower motor. Blower issues such as a faulty capacitor, loose fan belt or defective speed controller can cause the fan to run too slowly.

Condensate Lines Have Frozen

High-efficiency furnaces have condensate lines. If the lines run horizontally or at a shallow angle, the water may freeze, causing a buildup of condensate. This will cause furnace freezing and trigger the safety shutoff.

Furnace Vent Is Blocked

Heavy snow and ice may settle around the top of the vent and block it. Bird nests, leaves and debris can block the vent as well. A choked vent can result in back pressure that triggers a furnace safety shutdown.

Burner Isn't Working Properly

A dirty fuel burner will cause the furnace to run inefficiently. Signs include yellow or orange flames, difficulty starting and poor heat output. The burner should be checked and cleaned once a year.

Furnace Shuts Down Repeatedly

The furnace runs for a brief time, then shuts off, and you have restart it manually. Common reasons for this are:

• Faulty or dirty flame sensor. The flame sensor signals the controller that the furnace is operating. If the sensor is degraded or contaminated by soot from faulty burners, the controller can assume the furnace isn't running and shut off the fuel supply.

• Pilot light isn't working properly. Older furnaces are equipped with a pilot light to ignite the burner. If it gets dirty or blocked, the pilot light may go out.

• High limit switch issues. Furnaces have a high temperature sensor that shuts off the equipment if it gets too hot. A dirty or faulty sensor can shut down the furnace prematurely.

Avoid Furnace Problems by Getting It Checked Before Winter

You can avoid most furnace cold-weather issues through regular servicing and inspection. If you've experienced winter furnace problems, ask your heating, ventilation and air conditioning (HVAC) technician to check if your furnace is correctly sized or needs replacing.