how to defrost hvac unit in winter

How to Defrost HVAC Unit in Winter

Centralized HVAC systems have outdoor components that can withstand the elements regardless of the season. However, freezing still occurs. A frozen HVAC unit can lead to substantial problems and discomfort, so it’s good to know how to defrost an HVAC unit in winter. 

Eastern Shore Heating & Air Conditioning has thousands of satisfied customers, including those with frozen HVAC units in the winter. Here, our HVAC service explains why the issue occurs and the steps to take if it happens. 

What Causes the HVAC Unit to Freeze?

Centralized HVAC systems or reversible air conditioners with heat pumps have an outdoor component called a condenser unit. Their design allows them to withstand most weather conditions. Still, freezing temperatures can become too much for a heating and cooling system if it cannot thaw. 

When the heat pump operates in “heat mode,” it transfers warm air from outdoors to your home’s interior using refrigerant. When the heat transfer starts, condensation can form on the outdoor coil. The moisture on the component will freeze unless the heat pump defrosts the ice. 

Ice on the outdoor HVAC unit isn’t always bad. Problems develop if the defrost cycle doesn’t start or if too much snow and ice accumulate on the equipment, leading to a lack of airflow. 

Restricted airflow is one of the top reasons an outdoor unit freezes. Dirty air filters and leaves, plants, snow, and other debris surrounding your HVAC’s outdoor unit can impede airflow.

For maximum airflow, leave at least 30 inches of space between the equipment and the building’s exterior wall. This distance will prevent debris, snow, furniture, and other objects from blocking the unit’s cooling slats. 

Can Heat Pumps Freeze?

Property owners in warmer climates tend to use heat pumps instead of furnaces to save money on energy costs. The general assumption is that reversible air conditioners aren’t suitable for cold temperatures because they will freeze.

Thanks to technological developments, you can now purchase heat pumps outfitted for cold-weather climates. In 2023, Energy Star will introduce a certification mark on cold-climate heat pumps that notifies customers the appliance can perform efficiently in cold temperatures. 

It’s not uncommon for heat pumps to freeze while in heat mode. Manufacturers include a defrost mode in the equipment that blows hot air outside the system to adjust for the cold air blower inside it. The defrost mode will automatically run every 30, 60, or 90 minutes to melt ice on the condenser unit. 

How Can You Unfreeze an HVAC Unit?

The first step in learning how to defrost an HVAC unit in winter is to put the thermostat in “fan mode.” When running the system on fan mode for a few hours, its defrost mode kicks in to thaw its frozen components. The ice should melt without additional assistance. 

Once the defrost cycle is complete and the ice is gone, you can turn on your HVAC system. You might consider pouring hot water on the condenser unit, but that’s a bad idea. Running water on ice or attempting to break up the ice with something sharp can damage your system or make the system refreeze.

If the defrost cycle doesn’t eliminate the ice, contact an HVAC professional. The equipment likely has other issues contributing to the freeze. 

Why the Defrost Cycle Stops Working

You might realize the reversible air conditioner’s defrost cycle isn’t working correctly if it turns on when no ice is present. In other cases, the process might not start at all. The problem could be a faulty thermostat, electrical wiring issues, or a dirty outdoor coil. 

A heat pump that isn’t working correctly likely lacks a functional defrost mode. Without an inspection and repairs, the issue could lead to additional HVAC system problems. It will also become difficult for the unit to thaw ice and snow if accumulations become too thick. 

Learn More About Winter HVAC Care and Maintenance

Many factors contribute to your heating and cooling system’s performance during the winter, including dirty air filters and not knowing how to size an HVAC system. Understanding how to defrost an HVAC unit in winter and relying on professional technicians at Eastern Shore Heating & Air Conditioning will ensure your system runs smoothly throughout the year.

With over 40 years of experience, our top-rated, fully licensed team has the tools and expertise to install, repair, and maintain any HVAC system in Central New Jersey. Request a free estimate from our certified technicians by calling (732) 800-9416 or completing our online form.