Strategies for Preventing a Heat Pump from Freezing in Cold Weather - Experts Offer Their Recommendations on What to Do and What to Avoid During Frigid Spells

Maintaining a heat pump's efficiency, especially during cold weather, is crucial to ensure smooth operation. Here's a step-by-step guide on how to identify and resolve common heat pump freezing issues.

Identifying the Problem

If you notice frost or ice buildup on the outdoor unit or coils, unusual loud humming sounds, water puddles under the unit, reduced heating performance, frequent system shutdowns, poor airflow, or diagnostic error codes, your heat pump might be freezing.

Common Causes and Resolutions

Restricted airflow: Dirty filters, blocked vents, leaves, or obstructions can limit warm air circulation, causing coils to get too cold and ice to form. Regularly clean or replace air filters and clear vents and debris around the unit to ensure proper airflow.
Low refrigerant levels: Due to leaks or improper charge, coils may become too cold, freezing moisture on the coil surface. Have a certified technician check refrigerant pressure with gauges and professionally recharge if low; repair any leaks.
Faulty or inadequate defrost cycle: Broken sensors or timers can prevent the proper melting of ice buildup on outdoor coils. Test the defrost cycle and repair or replace malfunctioning sensors/timers to ensure appropriate defrosting.
Fan or blower malfunctions: Insufficient warm air circulation over coils leads to ice formation. Inspect and repair/replace faulty fans or motors to restore proper airflow.
Poor drainage: Meltwater freezing again on or near coils can cause freezing. Ensure drain lines and drainage paths are clear and unobstructed.
Incorrect heat pump sizing or installation: In extreme cold, a unit that struggles, cycles inefficiently, or short cycles may freeze. Have the system evaluated for correct sizing and proper placement, consider supplemental heating if needed.

Additional Troubleshooting Tips

Regularly inspect and clean both indoor and outdoor coils to maintain efficiency and prevent freezing.
Avoid thermostat placement near heat sources or direct sunlight to prevent false cycling.
Monitor for error or fault codes on your heat pump control panel and consult the manual for targeted fixes.
Be aware that very low outdoor temperatures can naturally reduce heat pump efficiency, and supplemental heating may be necessary.

When handling refrigerant or electrical repairs, always contact certified HVAC professionals for safety and compliance.

Choosing the Right Heat Pump

Choosing the right type of heat pump, such as solar-assisted heat pumps, is important to optimise efficiency and performance in various weather conditions.

Experts, like David Hilton, Homebuilding & Renovating's renewables expert, and Peter Spurway from Viessmann, discuss the importance of maintaining heat pumps and preventing freezing. They emphasise that correctly installed heat pumps from reputable manufacturers should not freeze in cold weather if they are functioning correctly.

If you suspect your heat pump is frozen, do not attempt to defrost it by pouring water on it or chipping away at the ice, as it is dangerous and can cause damage. Instead, contact an HVAC professional for assistance. Ignoring the problem can lead to future issues with the unit.

When the heat pump gets completely blocked with ice, it will be visible on the back of the heat pump and the output of the heat pump will drop, preventing it from heating water or the home adequately. The defrost function on a heat pump allows it to momentarily reverse to melt ice build-up on the evaporator.

Low temperatures and high humidity can cause a heat pump to freeze in winter. By systematically checking airflow, refrigerant level, defrost operation, and physical condition of the unit, most freezing issues can be diagnosed and resolved.

In order to maintain the efficiency of a heat pump during cold weather, it's crucial to identify and address freezing issues promptly.
If frost or ice is accumulating on the outdoor unit or coils, it might be a sign of a freezing heat pump.
Other symptoms include unusual loud humming sounds, water puddles under the unit, reduced heating performance, frequent system shutdowns, poor airflow, or diagnostic error codes.
Restricted airflow due to dirty filters, blocked vents, leaves, or obstructions can lead to coils getting too cold and ice forming.
Regularly cleaning or replacing air filters and clearing vents and debris around the unit helps ensure proper airflow, preventing freezing.
Low refrigerant levels caused by leaks or improper charge can also make coils too cold, leading to ice formation.
A certified technician should check refrigerant pressure with gauges and recharge if low, while repairing any leaks to resolve this issue.
A faulty or inadequate defrost cycle, often caused by broken sensors or timers, prevents proper ice melting on outdoor coils.
Testing the defrost cycle and repairing or replacing malfunctioning sensors/timers ensures appropriate defrosting.
Additionally, inspecting and repairing/replacing faulty fans or motors, maintaining drain lines, and choosing the right heat pump like solar-assisted heat pumps can help minimize freezing problems.