What is the Most Common Cause of Furnace Short Cycling?

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If you have ever noticed your furnace turning on and off more frequently than usual, you are encountering a problem that is known as short cycling. This not only disrupts the comfort of your home but can also take a toll on your furnace’s efficiency and longevity. Air Supply Heating & Air Conditioning would like to explore why short cycling occurs and how it can be resolved.

What is Furnace Short Cycling?

Short cycling happens when your furnace kicks off too soon before reaching the desired temperature, only to restart a short time later. This repeated on-and-off cycle strains the furnace and can lead to increased wear and tear.

Common Causes of Short Cycling

Oversized Furnace: One of the most common reasons for short cycling is having a furnace that is too large for the space it’s heating. An oversized furnace heats the home quickly, then shuts off, resulting in frequent cycles.


Dirty or Clogged Air Filters: A dirty air filter restricts airflow, causing the furnace to overheat and shut down prematurely. Regularly replacing or cleaning the air filters can prevent this issue.


Thermostat Issues: A malfunctioning thermostat, or one that’s placed in a spot with drafts or direct sunlight, can misread the actual temperature, leading to short cycling.


Exhaust Vent Blockage: Blocked or restricted exhaust vents can cause the furnace to overheat and shut off. Regular inspection of vents can ensure they are clear of debris and blockages.


Overheating Furnace: If the furnace’s internal temperature reaches unsafe levels, the system will shut off to prevent damage. Overheating can be due to various issues, including airflow problems and mechanical failures.

What are the Effects of Short Cycling?

Frequent starting and stopping puts extra strain on your furnace, leading to quicker wear and potential breakdowns. Short cycling can also cause your furnace to run inefficiently, which can lead to higher energy costs. Lastly, this constant on-and-off cycle can result in uneven heating and reduced comfort levels in your home.

How Do You Fix Short Cycling?

Correct Sizing of the Furnace: Ensure your furnace is correctly sized for your home. If it’s too big, it may be worth considering a more appropriately sized replacement.


Regular Furnace Maintenance: Regular servicing of your furnace can help detect and resolve issues that might cause short cycling.


Replace Air Filters: Change or clean your furnace’s air filters regularly to ensure proper airflow.


Thermostat Placement & Function: Check the location of your thermostat. It should be away from drafts, direct sunlight, and other sources of heat or cold. If it’s malfunctioning, consider replacing it.


Inspect and Clear Vents: Regularly check and clear any blockages in the vents and ductwork.


When to Call a Professional Heating Contractor: If you are unable to determine the cause of the short cycling, or if it continues after you have tried these solutions, it is time to call in a professional HVAC technician. They can diagnose and fix the problem, ensuring your furnace runs efficiently and safely.

Understanding and addressing the causes of furnace short cycling is key to maintaining an efficient, effective, and long-lasting heating system. Regular maintenance and addressing problems early can save you from bigger, more costly issues down the line, keeping your home cozy and comfortable all winter long. For furnace and other HVAC services, contact Air Supply Heating & Air Conditioning today.

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