The refrigerant cycle is the process by which the refrigerant circulates through the four main components of an HVAC system: the compressor, condenser, expansion valve, and evaporator. This closed cycle within the HVAC equipment allows the system to heat or cool the air and distribute it throughout the building.
Core Components of the Refrigeration Cycle
The four major components of the refrigerant cycle include:
1. Compressor
The compressor (outdoor unit) pressurizes and circulates refrigerant throughout the HVAC system. Before entering the compressor, the refrigerant is a low-pressure gas. The compressor increases its pressure and temperature and moves it to the condenser.
2. Condenser
The condenser, also called the condenser coil, is located in the outdoor unit. As the refrigerant passes through the condenser coil, the high-pressure refrigerant gas from the compressor is condensed into a liquid while also releasing the absorbed indoor heat.
3. Expansion Valve
After leaving the condenser as a high‑pressure liquid, the refrigerant passes through the expansion valve. This device rapidly drops the refrigerant’s pressure and temperature, creating a cold, low‑pressure mixture of liquid and vapor before it enters the evaporator.
4. Evaporator
This low-pressure liquid refrigerant then flows into the evaporator coil installed in the indoor unit. The evaporator coil absorbs the heat inside your home and turns the liquid back into a gas. The refrigerant then flows back to the compressor, where the cycle starts all over again, and cool air is distributed indoors.
In winter, heat pumps reverse the refrigeration cycle to move heat from the outdoor air into the home.
When this happens, the refrigerant flows in the opposite direction, causing the components to switch roles: the condenser becomes the evaporator, and the evaporator becomes the condenser. This reversal allows the heat pump to extract heat from the outdoors and bring it inside. This process is repeated to provide consistent heating.
Common Issues That Impact the Refrigeration Cycle
Typical issues in the refrigeration cycle affect system pressures, temperatures, and overall performance.
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Low Refrigerant
Low refrigerant disrupts the refrigeration cycle by reducing system pressure. With less refrigerant flowing through the evaporator, the coil can become too cold and start to freeze, restricting airflow and reducing cooling. The system then runs longer; the compressor works harder, and the chances of overheating increase.
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Refrigerant Leak
Refrigerant leak results from tiny holes or cracks in the coils. It affects the refrigeration cycle by reducing the system’s ability to absorb and transfer heat, forcing the system to run longer and less efficiently.
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Dirty Condenser Coil
Dirty coils block proper heat transfer, forcing your AC to work harder and cycle more often while using more energy. As debris builds up, refrigerant can’t absorb or release heat correctly, causing pressures to rise and putting extra strain on the compressor. If ignored, this added stress can shorten equipment life and increase the risk of system failure.
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Reversing Valve Fault in Heat Pumps
A faulty reversing valve disrupts the heat pump’s ability to switch between heating and cooling. Instead of sending refrigerant in the correct direction, it may get stuck in one mode, not shift fully, or leak internally. This breaks the normal refrigerant flow, leading to poor heating or cooling, reduced efficiency, and temperature imbalance.
