Heat pump system and controller for controlling operation of the same

A controller for controlling operation of a heat pump system,

• the heat pump system comprising:
• a compressor;
• a heatsource-side heat exchanger configured to cause heat exchange between refrigerant flowing therein and fluid passing therethrough;
• a utilization-side heat exchanger configured to cause heat exchange between refrigerant flowing therein and fluid passing therethrough;
• a high-pressure refrigerant pipe connected to each of a discharge port of the compressor and the heatsource-side heat exchanger;
• a liquid refrigerant pipe connected to each of the heatsource-side heat exchanger and the utilization-side heat exchanger;
• a low-pressure refrigerant pipe connected to each of the utilization-side heat exchanger and a suction port of the compressor;
• a liquid-side on-off valve disposed in the liquid refrigerant pipe;
• an expansion disposed in the liquid refrigerant pipe;
• and
• a gas-side on-off valve disposed in the low-pressure refrigerant pipe,
• the controller being configured to control the heat pump system to perform, when the occurrence of refrigerant leakage has been detected, a refrigerant recovery operation for recovering refrigerant from a utilization-side piping section to a heatsource-side piping section by operating the compressor while the liquid-side on-off valve is closed and the gas-side on-off valve is open,
• the utilization-side piping section extending between the liquid-side on-off valve and the gas-side on-off valve and including at least the utilization-side heat exchanger,
• the heatsource-side piping section extending between the gas-side on-off valve and the liquid-side on-off valve and including at least the compressor,
• wherein
• the controller is configured to, in the refrigerant recovery operation,
• control the heat pump system such that the gas-side on-off valve starts closing when a predetermined valve-close condition is satisfied during the compressor is operating for recovering refrigerant, and such that the operation of the compressor for recovering refrigerant stops after the closing of the gas-side on-off valve started, and
• control the compressor such that operation of the compressor stops when a predetermined compressor-stop condition is satisfied after the gas-side on-off valve has started closing, and wherein
• the predetermined compressor-stop condition includes at least one of:
• a first condition that change rate of pressure of refrigerant flowing in the high-pressure refrigerant pipe is below a first predetermined change rate value and change rate of pressure of refrigerant flowing in the low-pressure refrigerant pipe is below a second predetermined change rate value which is equal to or different from the first predetermined change rate value;
• and
• a second condition that pressure of refrigerant flowing in the low-pressure refrigerant pipe is below a second predetermined suction pressure value which is lower than the first predetermined suction pressure value.