Abstract: Operation switching units, each changing directions of a refrigerant flowing through its associated indoor unit in response to a switch from a cooling operation to a heating operation, or vice versa, are each connected with the associated indoor unit through indoor communication pipes; a gas-liquid separation unit is connected with an outdoor unit through outdoor communication pipes; and the operation switching units are connected with the gas-liquid separation unit through two intermediate communication pipes preinstalled and one intermediate communication pipe newly installed. This provides a simple and cost-effective means for upgrading a preinstalled air conditioner making a switch from cooling to heating, and vice versa, into an air conditioner that can perform a cooling operation and a heating operation in parallel with each other.

Abstract: A heat source unit includes a compressor, first and second heat exchangers connected in parallel, first and second motor-operated valves regulating amounts of refrigerant that flow to the first and second heat exchangers, first and second temperature sensors measuring temperatures of refrigerant flowing from the first and second motor-operated valve to the first and second heat exchangers, a discharge temperature sensor measuring temperature of refrigerant discharged from the compressor, and a valve opening controller. The controller regulates valve openings of the first and second motor-operated valves based on the discharge temperature, refrigerant temperature detected by the first temperature sensor and refrigerant temperature detected by the second temperature sensor.

Abstract: Operation switching units, each changing directions of a refrigerant flowing through its associated indoor unit in response to a switch from a cooling operation to a heating operation, or vice versa, are each connected with the associated indoor unit through indoor communication pipes; a gas-liquid separation unit is connected with an outdoor unit through outdoor communication pipes; and the operation switching units are connected with the gas-liquid separation unit through two intermediate communication pipes preinstalled and one intermediate communication pipe newly installed. This provides a simple and cost-effective means for upgrading a preinstalled air conditioner making a switch from cooling to heating, and vice versa, into an air conditioner that can perform a cooling operation and a heating operation in parallel with each other.

Abstract: In a refrigeration apparatus, in a first operation mode, a comparison is made between a first liquid pipe temperature, which is a temperature of a refrigerant on a side of a liquid pipe heat exchanger that is near usage-side heat exchangers, and a second liquid pipe temperature, which is a temperature of the refrigerant on a side of the liquid pipe heat exchanger that is near a plurality of heat-source-side heat exchangers, the liquid pipe heat exchanger performing heat exchange with the refrigerant flowing through liquid sides of the heat-source-side heat exchangers. When an evaporation-switch liquid pipe temperature condition is satisfied, the heat-source-side heat exchanger functioning as a radiator of the refrigerant is switched to an evaporator of the refrigerant, and the first operation mode is switched to a second operation mode in which the plurality of heat-source-side heat exchangers are caused to function as evaporators of the refrigerant.

Abstract: This air conditioner performs a cooling operation and a heating operation in parallel with each other with an outdoor unit and indoor units connected together through two communication pipes. The air conditioner includes a switching mechanism changing the directions of refrigerants flowing through the communication pipes depending on whether a heating dominant operation is being performed in a first load region where a cooling load is relatively light or a second load region where the cooling load is heavier than in the first load region. In the second load region, the switching mechanism allows a low-pressure refrigerant to flow from the indoor units to the outdoor unit through the second communication pipe thicker than the first communication pipe to reduce a performance deterioration due to the pressure loss involved with the heating dominant operation.

Abstract: Operation switching units, each changing directions of a refrigerant flowing through its associated indoor unit in response to a switch from a cooling operation to a heating operation, or vice versa, are each connected with the associated indoor unit through indoor communication pipes; a gas-liquid separation unit is connected with an outdoor unit through outdoor communication pipes; and the operation switching units are connected with the gas-liquid separation unit through two intermediate communication pipes preinstalled and one intermediate communication pipe newly installed. This provides a simple and cost-effective means for upgrading a preinstalled air conditioner making a switch from cooling to heating, and vice versa, into an air conditioner that can perform a cooling operation and a heating operation in parallel with each other.

Abstract: A refrigeration apparatus includes a compressor, a heat source-side heat exchanger, a receiver, a utilization-side heat exchange, a receiver degassing pipe interconnecting an upper portion of the receiver and a suction side of the compressor, and a receiver liquid level detection pipe connected to the receiver. The receiver liquid level detection pipe detects whether or not liquid level in the receiver has reached a predetermined position on a lower side of a position where the receiver degassing pipe is connected. The receiver liquid level detection pipe merges with the receiver degassing pipe via a capillary tube. The receiver degassing pipe has a refrigerant heater to heat refrigerant flowing through the receiver degassing pipe. Whether or not the liquid level in the receiver has reached the predetermined position is detected using a temperature of refrigerant flowing though the receiver degassing pipe.

Abstract: In a refrigeration apparatus, in a first operation mode, a comparison is made between a first liquid pipe temperature, which is a temperature of a refrigerant on a side of a liquid pipe heat exchanger that is near usage-side heat exchangers, and a second liquid pipe temperature, which is a temperature of the refrigerant on a side of the liquid pipe heat exchanger that is near a plurality of heat-source-side heat exchangers, the liquid pipe heat exchanger performing heat exchange with the refrigerant flowing through liquid sides of the heat-source-side heat exchangers. When an evaporation-switch liquid pipe temperature condition is satisfied, the heat-source-side heat exchanger functioning as a radiator of the refrigerant is switched to an evaporator of the refrigerant, and the first operation mode is switched to a second operation mode in which the plurality of heat-source-side heat exchangers are caused to function as evaporators of the refrigerant.

Abstract: A refrigeration apparatus includes a refrigerant circuit connecting heat-source units in parallel with usage units. First and second heat-source units have first and second compressors, first and second heat-source-side heat exchangers, first and second high-pressure receivers, first and second detecting elements detecting whether the receivers are near flooding, first and second bypass channels returning refrigerant in top parts of the receivers to intake sides of the compressors, and first and second motor-operated valves on the bypass channels, respectively. A controller performs excess refrigerant distribution control in which an opening degree of the first valve is controlled to be greater than an opening degree of the second valve when the second detecting element detects a nearly flooded state, and the opening degree of the second valve is controlled to be greater than the opening degree of the first valve when the first detecting element detects a nearly flooded state.

Abstract: A refrigeration apparatus includes a refrigerant circuit connecting heat-source units in parallel with usage units. First and second heat-source units have first and second compressors, first and second heat-source-side heat exchangers, first and second high-pressure receivers, first and second detecting elements detecting whether the receivers are near flooding, first and second bypass channels returning refrigerant in top parts of the receivers to intake sides of the compressors, and first and second motor-operated valves on the bypass channels, respectively. A controller performs excess refrigerant distribution control in which an opening degree of the first valve is controlled to be greater than an opening degree of the second valve when the second detecting element detects a nearly flooded state, and the opening degree of the second valve is controlled to be greater than the opening degree of the first valve when the first detecting element detects a nearly flooded state.

Abstract: A heat source unit includes a compressor, first and second heat exchangers connected in parallel, first and second motor-operated valves regulating amounts of refrigerant that flow to the first and second heat exchangers, first and second temperature sensors measuring temperatures of refrigerant flowing from the first and second motor-operated valve to the first and second heat exchangers, a discharge temperature sensor measuring temperature of refrigerant discharged from the compressor, and a valve opening controller. The controller regulates valve openings of the first and second motor-operated valves based on the discharge temperature, refrigerant temperature detected by the first temperature sensor and refrigerant temperature detected by the second temperature sensor.

Abstract: A refrigeration apparatus includes a compressor, a heat source-side heat exchanger, a receiver, a utilization-side heat exchange, a receiver degassing pipe interconnecting an upper portion of the receiver and a suction side of the compressor, and a receiver liquid level detection pipe connected to the receiver. The receiver liquid level detection pipe detects whether or not liquid level in the receiver has reached a predetermined position on a lower side of a position where the receiver degassing pipe is connected. The receiver liquid level detection pipe merges with the receiver degassing pipe via a capillary tube. The receiver degassing pipe has a refrigerant heater to heat refrigerant flowing through the receiver degassing pipe. Whether or not the liquid level in the receiver has reached the predetermined position is detected using a temperature of refrigerant flowing though the receiver degassing pipe.

Abstract: This air conditioner performs a cooling operation and a heating operation in parallel with each other with an outdoor unit and indoor units connected together through two communication pipes. The air conditioner includes a switching mechanism changing the directions of refrigerants flowing through the communication pipes depending on whether a heating dominant operation is being performed in a first load region where a cooling load is relatively light or a second load region where the cooling load is heavier than in the first load region. In the second load region, the switching mechanism allows a low-pressure refrigerant to flow from the indoor units to the outdoor unit through the second communication pipe thicker than the first communication pipe to reduce a performance deterioration due to the pressure loss involved with the heating dominant operation.

Abstract: Operation switching units, each changing directions of a refrigerant flowing through its associated indoor unit in response to a switch from a cooling operation to a heating operation, or vice versa, are each connected with the associated indoor unit through indoor communication pipes; a gas-liquid separation unit is connected with an outdoor unit through outdoor communication pipes; and the operation switching units are connected with the gas-liquid separation unit through two intermediate communication pipes preinstalled and one intermediate communication pipe newly installed. This provides a simple and cost-effective means for upgrading a preinstalled air conditioner making a switch from cooling to heating, and vice versa, into an air conditioner that can perform a cooling operation and a heating operation in parallel with each other.