As winter’s icy grip tightens, homeowners rely heavily on their heating systems to combat the plummeting temperatures. However, a perplexing issue can arise, leaving many pondering, “Why is my heat pump freezing up in winter?” Understanding the causes behind this frosty phenomenon is crucial for maintaining a cozy and efficient home. Today, we’ll explain the potential culprits to blame when a heat pump freezes, and ultimately, the optimal solutions to thaw out your heat pump unit.

Understanding Freezing Up: A Frosty Dilemma

A heat pump works by extracting heat from the outdoor air and transferring it indoors to warm your home. In the winter, when temperatures plummet, the moisture in the cold air can condense on the heat pump’s outdoor unit. This condensation may freeze, forming a layer of frost or ice on the outdoor coil. While a thin layer is normal, excessive buildup can hinder the efficiency of the heat pump system and, if left unaddressed, lead to more severe problems.

The Culprits Behind a Frozen Heat Pump

Several factors can contribute to a heat pump freeze during the winter months. Identifying these culprits is essential for implementing effective solutions.

  • Low Refrigerant Levels: Inadequate levels of refrigerant can cause the coils in the outdoor unit to become too cold, leading to excessive ice formation. Regular maintenance, including checking and replenishing refrigerant levels, is crucial in preventing this issue.
  • Poor Airflow: Restricted airflow over the outdoor unit can impede heat exchange and contribute to freezing. Common causes include clogged air filters in the HVAC system, blocked vents, or debris around the unit. Regularly cleaning and maintaining these components can prevent airflow issues.
  • Defrost Cycle Issues: Modern heat pumps are equipped with a defrost cycle to melt accumulated ice, switching the heat pump unit into cooling mode as needed to warm the coils. During this time, emergency heat should warm the house, such as a backup gas furnace or auxiliary heat from electric coils. If the defrost mode or reversing valve malfunctions, it can lead to excessive ice forming on the outdoor coil. Regular inspections and timely repairs can ensure the proper functioning of the defrost cycle.
  • Thermostat Settings: Incorrect thermostat settings, such as a constant low temperature, can cause the heat pump to run continuously, promoting too much ice accumulation. Adjusting the thermostat to optimal settings can help mitigate this problem.
  • Outside Temperature Extremes: In extremely cold temperatures, the moisture in the air freezes more rapidly, exacerbating ice buildup on heat pumps. While this factor is beyond control, addressing other HVAC system issues can help minimize the impact of extreme temperatures.

Thawing the Chill: Solutions for a Frozen Heat Pump

If your heat pump has iced over and defrost mode isn’t thawing the ice, it’s time to take action. Here are some steps to take that will help you thaw ice accumulation on heat pumps:

  1. Turn Off the Heat Pump: As a first step, switch off the heat pump to prevent further ice buildup and potential damage.
  2. Clear Surrounding Debris: Remove any snow, ice, or debris around the outdoor unit to ensure proper airflow.
  3. Check for Obstructions: Inspect the outdoor coil and fins for any visible obstructions. Clear away leaves, twigs, or other debris that might impede the heat exchange process.
  4. Inspect Air Filters: Check and replace air filters if they are dirty or clogged. Restricted airflow can contribute to ice buildup, and clean filters ensure optimal performance.
  5. Use a Gentle Heat Source: If safe to do so, use a gentle heat source, such as warm water, to expedite the thawing process. Avoid using excessive heat or sharp objects that could damage the unit.


Remember, safety is paramount when dealing with a frozen heat pump. If you’re uncertain or the issue persists, it’s advisable to seek the expertise of HVAC professionals for a thorough inspection and necessary heat pump repairs. Heat pump experts can identify and address underlying issues, such as refrigerant leaks, a stuck reversing valve, or malfunctioning defrost function controls.

Contact Us for Heat Pump Repair Services

If you find yourself grappling with a frozen heat pump and the winter chill seems unyielding, it’s time to take action. Rusk Heating & Cooling is your reliable partner in ensuring a warm and comfortable home. Our seasoned professionals specialize in diagnosing and resolving heat pump issues, providing prompt and effective solutions. Don’t let a frozen heat pump leave you in the cold—contact us today for unparalleled heating system repair services.