Why Do Heat Pumps Fail in Winter?
In the depths of winter, when people need warmth the most, some air-source heat pumps can unexpectedly "strike"—heating performance drops, units cycle on and off frequently, or they fail to operate entirely. This not only compromises user comfort but can also cause irreversible damage to the equipment. Why do heat pumps, which perform excellently in summer, tend to encounter problems in winter? This article will delve into the root causes of winter heat pump failures from a technical perspective and provide professional solutions.
Chapter 1: The Winter Dilemma – Why Do Heat pumps Struggle in Low Temperatures?
The operating principle of an air-source heat pump involves absorbing thermal energy from the air via a refrigerant, which is then compressed to raise its temperature before being released into the water. This process is highly efficient and stable at normal temperatures. However, when winter temperatures plummet, heat pumps face multiple challenges.
1.1 Frosting: The "Winter Killer" of Heat Pumps
When the outdoor temperature drops below 0°C, condensation forms on the surface of the heat pump evaporator due to the temperature difference, which then freezes into frost. A certain amount of uniform frosting is normal and can be handled by the heat pump's automatic defrost function. However, problems arise when frosting becomes abnormal.
Five Critical Impacts of Frosting on Heat Pump Performance:
First, it blocks the gaps between fins, increasing resistance to airflow and causing a sharp decline in heat exchange efficiency.
Second, the frost layer increases the thermal resistance of the heat exchanger, significantly weakening the heat pump's ability to absorb heat from the air.
Third, it triggers frequent defrosting cycles. The defrosting process itself is essentially a cooling operation. Not only does it fail to heat water, but it also consumes heat from the existing hot water. The cold water discharged during defrosting flows back into the tank, further lowering the water temperature.
Fourth, as the evaporation temperature continues to drop, the Coefficient of Performance (COP) decreases sharply, leading to deteriorating operational performance.
Fifth, prolonged inefficient operation ultimately prevents the unit from working correctly, causing economic losses and concerns for the user.
1.2 Low-Temperature Degradation: Inescapable Physics
At temperatures of -10°C and below, conventional heat pumps face the challenge of excessively low evaporation temperatures. This leads to reduced refrigerant evaporation, insufficient refrigerant returning to the compressor, and a sharp decrease in condensation heat output—resulting in significant heating capacity degradation. Data shows that the heating capacity of ordinary heat pumps in low-temperature environments can drop by 30% to 50% or more.
Chapter 2: Decoding Failures: Analysis of Three Common Winter Fault Categories
Based on industry technical research and numerous field cases, winter heat pump failures can be categorized into the following three main types:
2.1 Failures Caused by External Environmental Factors
Phenomenon 1: The ambient temperature is above 0°C, but shortly after startup, the entire heat exchanger surface rapidly frosts, and the frost layer becomes increasingly thick. Indoor heating effect is poor, and defrosting cycles are frequent.
Root Cause Analysis: This is usually not the weather's fault, but rather "dirt blockage." Dirty fins on the heat exchanger, fan system malfunctions, or obstructions at the air intake or outlet impede airflow, causing localized low temperatures and triggering abnormal frosting.
Phenomenon 2: The outdoor unit is covered with thick ice, and the defrost mode is ineffective. If the automatic defrost function is faulty or fails to activate, the ice can completely block heat exchange, leaving the equipment in a "frozen" state.
2.2 Failures Caused by System Hardware
Refrigerant Issues:
Refrigerant Leakage: Manifests as frost starting at the bottom of the outdoor heat exchanger (near the capillary tube outlet) and spreading upwards. The system defrosts frequently, but heating performance remains poor. This occurs because insufficient refrigerant leads to excessively low evaporation pressure.
Refrigerant Overcharge: Manifests as frost on the upper half of the heat exchanger, spreading downwards. This is common after overcharging during maintenance, leading to excessively high pressure on the high-pressure side of the system.
Four-Way Valve Failure: The four-way valve is a critical component for switching the heat pump between cooling and heating modes. Common winter failures include:
Stuck Valve Core: The system locks in a single mode (e.g., cooling only).
Burnt-out Solenoid Coil: No magnetic force to drive the valve body.
Internal Leakage: Refrigerant bypasses internally, causing pressure imbalance and capacity degradation.
When the four-way valve fails, the heat pump may be unable to enter heating mode, or its heating effect will be severely compromised.
Electrical System Failures: Issues like tripped circuit breakers, blown fuses, or poor wiring connections can prevent the compressor or fan from operating correctly. Sometimes the fan runs, but there is no heat output—a "hidden" failure easily overlooked.
2.3 Failures Caused by Improper Maintenance
Clogged Filters: Failure to clean air-side filters or water circuit filters regularly can severely obstruct airflow or water flow, leading to system overheating or triggering safety protection shutdowns.
Sensor Malfunctions: Deviations in temperature or pressure sensors can cause the control system to misjudge operating conditions, leading to delayed or unnecessary defrosting cycles.
Failed Insulation: Damaged insulation on water pipes can cause the pipes to freeze in extremely cold weather, potentially even cracking the heat exchanger—one of the most severe winter failures.
Chapter 3: Technological Breakthrough: Flamingo's Winter Solutions
Facing the numerous challenges of winter operation, Flamingo has built a comprehensive protection system through continuous technological innovation.
3.1 Enhanced Vapor Injection (EVI) Technology: Solving Low-Temperature Degradation
Flamingo's North Star Series ultra-low temperature heat pumps feature advanced Enhanced Vapor Injection (EVI) technology. This technology injects intermediate-pressure gas into the compressor's intermediate chamber, achieving quasi-two-stage compression and significantly enhancing low-temperature heating capacity.
The operating principle involves adding an economizer (high-efficiency subcooler) to the system. This subcools the main refrigerant circuit while preheating refrigerant from the auxiliary circuit after expansion through an electronic expansion valve to a suitable intermediate pressure state, which is then injected back into the compressor for secondary compression. This innovation brings three major advantages:
Increased Heating Capacity: Compared to ordinary heat pumps, EVI technology can boost heating capacity by 50% to 80% in low-temperature environments.
Expanded Operating Range: Flamingo ultra-low temperature units can operate stably for heating in extreme environments down to -25°C to -30°C.
Guaranteed Efficiency: At -25°C, the COP can still reach 1.8 or higher.
3.2 Intelligent Defrost Control System: Precise Defrosting, Eliminating Misjudgment
"Defrost when frosted, don't defrost when clear"—this is the core principle of Flamingo's intelligent defrost control.
Traditional heat pumps often use timed defrost modes, which can easily lead to "unnecessary defrosting" or "failure to defrost when frosted." Flamingo's intelligent control system uses a comprehensive judgment based on multiple parameters:
Analysis of the temperature difference between the coil and the ambient air.
Monitoring of cumulative compressor operating time.
Dynamic assessment of heating capacity degradation.
Only when the system determines that the frost layer has reached a set threshold (e.g., the coil temperature is below the ambient temperature by a specific difference for a certain duration, or heating capacity degradation exceeds 20%) does it initiate a defrost cycle. This ensures effective defrosting while avoiding heat loss from unnecessary cycles.
3.3 High-Quality Core Components: The Foundation for Stable Operation
All Flamingo products utilize core components from internationally renowned brands:
Copeland EVI Compressors: Optimized for low-temperature conditions, featuring intermediate-stage refrigerant injection ports, achieving the effect of two-stage compression with a single compressor.
Fuji Koki (Saginomiya) Electronic Expansion Valves: Precisely control refrigerant flow with fast response and high regulation accuracy.
High-Efficiency Coaxial (Tube-in-Tube) Heat Exchangers: Utilize efficient heat transfer tubes, providing 3.7 times the heat exchange area of smooth tubes. The counterflow arrangement ensures outlet subcooling, enhancing system efficiency.
3.4 Multiple Anti-Freeze Protection Designs
To address the risk of freezing and cracking in winter, Flamingo units incorporate multiple layers of protection:
Power Failure Memory and Auto-Restart: Automatically resumes operation after power is restored following an unexpected outage.
Interlock Control for Pump and Unit: Ensures water circulation to prevent freezing.
Intelligent Anti-Freeze Operation Mode: Periodically starts the pump and compressor during standby mode to prevent pipes from freezing.
Chapter 4: User Guide: A Seven-Step Winter Maintenance Checklist
Even with advanced technology, correct usage and maintenance are crucial for ensuring your heat pump survives the winter safely. Here is Flamingo's winter maintenance guide for users:
4.1 Pre-Winter Inspection (Four Essential Steps)
Step 1: Clean the Area Around the Unit – Check for any obstructions around the outdoor unit to ensure proper airflow through the air intake and outlet. Clean dust, catkins, fallen leaves, and other debris from the fins.
Step 2: Inspect the Water System – Check pipes, pumps, and filters for blockages or leaks. Inspect pipe insulation for cracks or damage and repair or replace as needed.
Step 3: Check the Electrical System – Verify that wiring connections are secure and cables are undamaged. Clean any debris from the electrical control cabinet to ensure safety.
Step 4: Clean the Filters – Clean the water circuit strainers/filters to remove impurities. For new or recently modified systems, cleaning the underfloor heating loops or radiators is recommended to remove any deposited debris or rust.
4.2 Winter Operation Precautions
Step 5: Never Power Off – When using the heat pump in winter, ensure the main unit, water pump, and main power supply are NEVER turned off. Many users mistakenly believe they can power down the unit when not in use. However, doing so prevents the compressor crankcase heater from working, allowing refrigerant to migrate into the compressor. Upon restarting, this can cause liquid slugging and damage the compressor.
Step 6: Monitor Operating Status – Regularly check for unusual operating noises. Observe whether the frosting and defrosting cycles are regular. If you notice abnormal frosting (e.g., localized excessive frost, failure to defrost for extended periods), contact a professional for inspection promptly.
Step 7: Prepare for Extended Shutdown – If the unit will not be used for a long period, the water within the system piping and the unit's heat exchanger must be completely drained to prevent freezing and cracking. It is recommended to have this draining operation performed by a professional.
4.3 Warning Signs of Potential Failure
If you encounter any of the following, it may indicate an underlying issue with your heat pump, and prompt professional service is advised:
Abnormal Noises: Clicking, grinding, or vibrating sounds may indicate fan, compressor, or loose component issues.
Severe Icing: The outdoor unit is covered with thick ice, suggesting the automatic defrost function may have failed.
Noticeably Reduced Heating Capacity: The outlet water temperature fails to reach the set value, and the unit runs for extended periods.
Frequent On/Off Cycling or Failure to Start: The control system may have detected a fault and triggered a safety lockout.
Chapter 5: Industry Outlook – Future Directions for Heat Pump Technology
With the advancement of the "Dual Carbon" strategy, heat pump technology is facing unprecedented development opportunities. In addressing the issue of winter operational reliability, the industry is showing three major technological trends:
5.1 Application of Natural Refrigerants
CO₂ (R744) heat pump technology is maturing rapidly. As a natural refrigerant, CO₂ not only has zero ODP and extremely low GWP but also possesses excellent low-temperature performance. Flamingo's CO₂ heat pumps can stably produce hot water up to 90°C in -30°C environments, providing a zero-carbon solution for heating in cold regions and industrial heat applications.
5.2 Deep Integration of Intelligence
The future heat pump is not just a heating device but an intelligent terminal within the Energy Internet. By utilizing AI algorithms to learn user heat consumption habits, predict weather changes, and optimize operation strategies, heat pumps will ensure comfort while maximizing the use of off-peak electricity and solar PV energy, achieving optimal energy efficiency.
5.3 Extreme Environmental Adaptability
For applications in severely cold regions (temperatures of -35°C and below), cascade heat pump systems are becoming a focal point of R&D. Through the coordinated work of a high-stage and a low-stage system, they maintain efficient heating at extremely low temperatures while switching to single-stage operation in moderately cold environments, balancing both economy and reliability.
Conclusion: Reliable Technology + Correct Usage = Safe Winter Operation
Winter heat pump failures are not an inevitable fate. From a scientific perspective, most failures have underlying logical causes and external triggers. From a technological perspective, advanced EVI technology, intelligent defrost control, and high-quality core components have already built a powerful "cold-resistant" capability for modern heat pumps. From a user perspective, correct installation, proper maintenance, and timely attention to warning signs are the crucial "human factors" ensuring reliable operation.
As an innovative enterprise focused on heat pump water heating technology, Flamingo has always prioritized "All-Season Reliable Operation" as a core indicator in product development. Whether in the heat of summer or the bitter cold of winter, whether in humid southern regions or dry northern climates, Flamingo heat pumps are dedicated to providing users with stable, efficient, and comfortable hot water experiences.
The next time you enjoy warm water on a winter's day, remember: behind that warmth lies heat pump technology silently overcoming nature's cold, innovative design constantly challenging physical limits, and correct usage protecting the equipment's health. Winter, for a well-designed and properly maintained heat pump, should never be a season of failure.
