What Causes a Heat Pump to Freeze Up in DeSoto, TX?

Many Texas property owners now enjoy the energy efficiency and convenience of single-unit heating and cooling provided by modern heat pump HVAC systems. Heat pumps rely on compressed refrigerants to operate, which means they occasionally freeze up. 

Dial One Johnson Plumbing, Cooling & Heating presents the discussion below to cover what causes a heat pump to freeze up and how to address it. As the leading provider of expert heating repair services in DeSoto, TX, we’re here to help keep your living space safe and comfortable throughout the year. 

Low Refrigerant Levels

Refrigerant is essential for the heat transfer process, as it allows your heat pump to efficiently heat and cool your home. 

Leaks or poor maintenance lead to insufficient levels of chemical refrigerants, and that causes improperly low pressures inside the closed lines and coils that move it through the system.  Insufficient pressure in the evaporator coil leads to much lower temperatures that cause water vapor to freeze and form frost and ice on its surface.

In addition to visible ice buildup, signs of low refrigerant include: 

• Reduced heating efficiency 
• Hissing or bubbling sounds near the unit resulting from leaks
• Surging electricity bills as the system struggles to maintain consistent temperatures

Our long, hot Texas summers can strain HVAC systems, making refrigerant leaks more noticeable when cold weather arrives.  

Dirty Coils Prevent Proper Heat Exchange

What causes a heat pump to freeze up? Over time, heat pump coils collect dirt, dust, and debris, especially in our region where pollen counts run high. Dirty coils impair the efficient transfer of heat into and out of the coils.  

Here’s how dirty coils lead to freezing:

• Dirt acts as an insulator, reducing heat transfer efficiency.
• The system compensates by working harder, causing excessive cooling on the evaporator coil.
• Moisture that collects on the coil turns into ice, further blocking efficient heat transfer.

Regular coil cleaning and routine seasonal professional maintenance can prevent this issue. 

Blocked Airflow Restricts Proper Circulation

A heat pump relies on unobstructed airflow to function correctly. In DeSoto, TX, common reasons for blocked airflow include clogged air filters, obstructed ductwork, and debris around the outdoor unit.

Heat pumps depend on open airflow, and here’s what happens with blockages:

• Impaired airflow prevents proper heat exchange, leading to ice formation, as described above.
• The compressor can overheat and shut down prematurely.
• Indoor air circulation decreases, making the system work harder in the struggle to maintain the desired temperature. 

Faulty Defrost Cycle

Modern heat pumps use a built-in defrost cycle to remove ice buildup when outdoor temperatures drop. However, if this cycle malfunctions, you can expect ice formation that can adversely impact system performance.

What causes a heat pump to freeze up when a defrost cycle fails? Some of the reasons include: 

• A defective defrost sensor may not detect ice buildup
• A malfunctioning control board may prevent the system from switching to defrost mode
• Low refrigerant or dirty coils may cause excessive ice formation despite defrost cycle operation

Outdoor Temperature and Humidity Levels

While Texas winters are generally mild, our occasional extreme cold snaps and high humidity can increase the risk of heat pump freezing. 

In Texas, our outdoor temperatures can affect heat pump performance in different ways:  

• Whenever temperatures drop below 32°F, condensation on the coils can freeze.
• High humidity levels in DeSoto, TX, often accelerate ice buildup.
• Extended periods of subfreezing weather can overwhelm a system’s defrost cycle.

Poor Maintenance Increases the Risk of Freezing

We recommend scheduling regular, routine professional heat pump cleaning, inspection, and servicing to avoid the problems that lead to frozen coils. An HVAC system technician will check refrigerant levels and inspect for leaks, in addition to cleaning essential components professionally.

In addition, you should change your system’s filter no less than every 30 to 90 days. Also, keep the area around your outside unit free of dirt, vegetation, and other airflow obstructions.