The Four-Way Valve:

A Key Component in Reversible HVAC Systems

In refrigeration systems, it is essential to have a mechanism that allows for efficient and flexible regulation of refrigerant flow. This is where the four-way valve comes into play, a key component in reversible refrigeration circuits capable of providing both cooling and heating.

In a conventional refrigeration circuit, several essential elements can be found, such as the indoor unit, compressor, outdoor unit, and expansion valve. The refrigerant flows in a counterclockwise direction from the compressor to the condenser and then to the expansion valve, which expands the refrigerant and directs it towards the evaporator. This configuration ensures that the indoor unit always operates as an evaporator and the outdoor unit as a condenser, resulting in the system being in cooling mode.

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However, to enable the circuit to operate in both cooling and heating modes, it needs to be reversible. This is achieved by inserting a four-way valve in the compressor discharge line. This valve redirects the compressor discharge to the appropriate path for the machine to operate in either cooling or heating mode.

In cooling mode, the indoor unit acts as the evaporator, and the corresponding expansion valve allows the refrigerant to expand and pass through the indoor unit, generating the desired cooling effect. The refrigerant then flows to the four-way valve, which redirects it to the compressor suction line. Subsequently, the compressor discharges the refrigerant to the condenser, where heat is released to the surroundings.

To achieve heating mode, where the outdoor unit acts as the evaporator, a bidirectional flow is required, capable of rotating in both counterclockwise and clockwise directions. For this purpose, two expansion valves are installed instead of one. When the circuit operates in this direction, one expansion valve is activated while the other is bypassed by a check valve. The refrigerant flows through the active expansion valve and then to the outdoor unit, which now functions as the evaporator. The gases leaving the evaporator are directed to the compressor suction line, while the compressed gases from the compressor are directed to the indoor unit, which now operates as the condenser. After the condenser, the gases do not pass through the expansion valve but return to the active expansion valve through a check valve.

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The four-way valve plays a crucial role in reversing the refrigerant flow, allowing the refrigeration circuit to be reversible. Through an internal sliding mechanism, this valve redirects the refrigerant flow according to the operational mode’s requirements.

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