In an air-conditioning apparatus, a heat source side heat exchanger, intermediate heat exchangers, and use side heat exchangers are formed in separate bodies respectively and adapted to be disposed at separate locations one another. In a heat medium circulation circuit where the intermediate heat exchanger and the use side heat exchanger are connected, temperature sensors are installed. An anti-freezing operation mode is provided in which, when the detection temperatures of the temperature sensors become equal to or lower than a set temperature Ts while a compressor or pumps are stopped, the heat medium is circulated to perform anti-freezing of the heat medium.

A refrigerating and air-conditioning apparatus performs, even during a heating operation under air conditions leading to formation of frost, a defrosting operation while simultaneously continuing a heating operation and that improves comfort through heating by ensuring an appropriate amount of ventilation. A plurality of refrigeration cycles that are capable of independently performing a heating operation and a defrosting operation, are provided. A ventilation damper of an indoor unit in which a refrigeration cycle that performs a defrosting operation is installed is closed during a defrosting operation, and a ventilation damper of an indoor unit in which a refrigeration cycle that performs a heating operation is installed is controlled to achieve a required amount of ventilation corresponding to the indoor ventilation state.

An air-conditioning apparatus includes a suction-injection pipe that introduces a refrigerant in a liquid or two-phase state into a suction side of a compressor, an expansion device that is arranged at the suction-injection pipe, and a controller that regulates the suction-injection flow rate of a refrigerant introduced into the suction side of the compressor through the suction-injection pipe by controlling the opening degree of the expansion device.

In an air-conditioning apparatus including a plurality of indoor units connected to a heat medium converter and a plurality of remote controllers respectively provided for the indoor units, the remote controllers each include a temperature sensor that detect a temperature of a corresponding space to be air-conditioned, and are each configured to communicate with a heat medium converter controller of the heat medium converter and an indoor unit controller of the corresponding indoor unit, transmit an instruction to start and stop an operation and data related to rotation speed of an indoor air-sending device to the corresponding indoor unit controller, and transmit the instruction to start and stop the operation, and a target temperature and a temperature detected by the temperature sensor or a difference therebetween, to the heat medium converter controller.

An air-conditioning apparatus is capable of completing heat medium freeze prevention control more quickly by performing heat medium temperature rise control for raising the temperature of a cooled heat medium and includes a controller that adjusts a current opening degree of a bypass device at a bypass pipe to an opening degree, and that makes an adjustment such that the flow passage resistance in the case of the opening degree becomes equal to the flow passage resistance in the case of an opening degree before an expansion device is adjusted to a minimum opening degree.

An air-conditioning apparatus includes a temperature sensor for detecting a temperature of the heat medium sent from each of the intermediate heat exchangers to each of the use-side heat exchangers, and a temperature of the heat medium that has exited each of the use-side heat exchangers, an opening degree controller for regulating a flow rate of the heat medium through each of the heat medium flow control devices, and a computing unit for computing a usage capacity of each of the indoor units from a rotation speed of the pump, an opening degree of each of the heat medium flow control devices, temperatures detected by the temperature sensors, and power consumption of each of the indoor units, and proportionally dividing the power consumption for a common portion among each of the indoor units based on the computed usage capacity and the power consumption of the common portion.

An air conditioning system may include an outdoor unit including a compressor; at least one distributor connected to the outdoor unit and including a condenser and an evaporator that exchange heat between refrigerant and water; a plurality of heating pipes in communication with the condenser; a plurality of cooling pipes in communication with the evaporator; a plurality of fan coil units connected to the plurality of heating pipes or the plurality of cooling pipes; and a controller configured to perform a heating pipe search operation for matching a portion of the plurality of fan coil units with the plurality of heating pipes, and a cooling pipe search operation for matching another portion of the plurality of fan coil units with the plurality of cooling pipes, in parallel.

A heat-recovery-type refrigerating apparatus includes a compressor, a heat-source-side heat exchanger, and a plurality of usage-side heat exchangers, and refrigerant is sent from the usage-side heat exchanger functioning as a refrigerant radiator to the usage-side heat exchanger functioning as a refrigerant evaporator, whereby heat can be recovered between the usage-side heat exchangers. Here, a portion of the heat-source-side heat exchanger is configured as a precooling heat exchanger for always circulating high-pressure vapor refrigerant discharged from the compressor, and a refrigerant cooler for cooling an electrical equipment item is connected to a downstream side of the precooling heat exchanger.

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.

An air conditioner includes an outdoor unit, a plurality of mode change devices including at least one mode changer including a branch duct and a changing valve, and configured to receive a control signal from the outdoor unit to control an operation of the at least one mode changer. A plurality of indoor units are connected to the outdoor unit or the plurality of mode change devices. The outdoor unit may determine an operation mode to operate the plurality of mode change devices a plurality of times. Each of the plurality of indoor units may detect a temperature change of an indoor heat exchanger in response to the operation of the mode change devices, to determine the number of connected mode changers and a connectable mode changer candidate group based on the temperature change of the indoor heat exchanger.