Your home's HVAC system can't run without proper airflow. For a natural gas furnace, airflow through the system serves several purposes. The air movement across the heat exchanger provides heat to your home but also prevents the heat exchanger from becoming too hot. Likewise, the furnace needs a steady supply of combustion air and a clear exhaust flue to operate efficiently and safely.
Anything that impacts these three critical types of airflow can reduce efficiency, stop your furnace from working, or even create hazardous conditions in your home. Unfortunately, it's not always easy to spot airflow problems before they cause more damage. These three warning signs will help you recognize if something might be wrong with your furnace so you can avoid potentially costly consequences.
1. Long Running Times
Furnaces work by blowing warm air through your vents until the thermostat stops calling for heat. This design has a few wrinkles with more advanced furnaces, but all home heating systems essentially work the same way. Your original installers designed your ducting system to provide adequate so your furnace can achieve this goal without running too long.
If you notice your furnace taking forever to bring your home up to your thermostat setpoint, it may be due to an airflow problem. With reduced airflow through your ductwork, your furnace will struggle to push enough heat through your home. As a result, your home will stay colder for longer, and you'll waste far more fuel to bring your home up to temperature.
2. Short Running Times
It may sound a bit counterintuitive, but short running times are another potential symptom of an airflow restriction. A minor restriction will cause your system to run for too long as it struggles to heat your home, but a substantial restriction will stop enough air from moving across your heat exchanger. Unfortunately, overheating can produce expensive and potentially dangerous problems.
Since overheating your heat exchanger is a major issue, all furnaces include limit switches to shut off the burner and allow the heat exchanger to cool. If your furnace runs for a short while and then shuts down before heating your home, the problem may be an airflow restriction repeatedly triggering your limit switch. This condition is known as short cycling.
3. Trouble Starting
A furnace requires oxygen and fuel for clean combustion, and modern furnaces also require negative pressure to pull combustion gases away from the combustion chamber. While somewhat different from airflow restrictions that affect your ductwork, a restriction in your furnace's air intake or exhaust systems can also cause trouble.
In many cases, your furnace will refuse to run since these restrictions will trigger safety devices such as the flame rod or the draft pressure switch. However, your furnace may also struggle to start but eventually fire up. This situation can occur if the airflow path through the combustion chamber is partially restricted and prevents the furnace from firing on the first try.
Contact residential HVAC repair services to learn more.