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.

A channel on an upstream side of a third expansion device and a channel on an upstream side of a second expansion device are connected during a heating operation, and medium pressure refrigerant generated by the third expansion device during the heating operation is introduced on a suction side of a compressor via the second expansion device and a suction injection pipe.

A refrigerant control system includes: a charge module configured to determine an amount of refrigerant that is present within a first portion of a refrigeration system within a building; and an isolation module configured to selectively open and close an isolation valve of the refrigeration system and to, via the isolation valve, maintain the amount of refrigerant within the first portion within the building below a predetermined amount of the refrigerant.

According to one embodiment, an air conditioner carries out a heating operation, a cooling operation, a cooling/heating mixed operation in which a higher priority is given to cooling, and a cooling/heating mixed operation in which a higher priority is given to heating.

An air conditioning apparatus includes an outdoor device that is configured to circulate refrigerant and that includes a compressor and an outdoor heat exchanger, a plurality of indoor devices configured to circulate water, and a heat exchange device connecting the outdoor device with the indoor device. The heat exchange device includes a heat exchanger configured to exchange heat between the refrigerant and the water, and a switch device configured to control flow of refrigerant between the indoor devices and the heat exchanger.

The present invention has an object to provide a refrigeration cycle apparatus. A refrigeration cycle apparatus according to the present invention includes: a compressor; and a control apparatus configured to calculate a rotation number command of the compressor. The control apparatus includes a capacity controller configured to calculate the rotation number of the compressor as a capacity rotation number, a protection controller configured to calculate the rotation number of the compressor as a protection rotation number and a rotation number selection unit configured to select any one of the capacity rotation number and the protection rotation number as the rotation number command of the compressor. The rotation number command of the compressor is calculated so that at least any one of causing the current capacity value to approach the capacity target value and causing the protection variable to approach the protection target value is satisfied.

A heat pump cycle includes a compressor, a heat exchanger, a gas-liquid separator, and an outdoor heat exchanger. The heat pump cycle includes a main circuit connecting the compressor, the heat exchanger, the gas-liquid separator, and the outdoor heat exchanger such that refrigerant flows therethrough. The heat pump cycle includes an exhaust-heat recovery heat exchanger, and an exhaust-heat recovery circuit forming a flow path leading to the compressor not through the outdoor heat exchanger but through the exhaust-heat recovery heat exchanger. The heat pump cycle includes an expansion valve that is disposed upstream of the exhaust-heat recovery heat exchanger in the exhaust-heat recovery circuit and expands the refrigerant such that the refrigerant changes from liquid phase to gas phase in the exhaust-heat recovery heat exchanger.

A heat source system includes heat source apparatuses each with refrigerant circuit and water heat exchanger. A water supply header pipe merges and supplies, to a load, water flowing in from the heat exchangers. A water return header pipe splits, into the heat exchangers, water flowing in from the load. Pumps feed water to the heat exchangers. A bypass pipe with bypass valve connects the supply and return header pipes. A differential pressure gauge measures a water pressure difference between supply and return. A controller determines the number of heat source apparatuses to operate, from heat generated by refrigerant circuits and heat required, determines whether an operating frequency of the pump connected to a heat source apparatus to be operated is a minimum frequency, and controls the pump operating frequency and/or an opening degree of the bypass valve such that the water pressure difference falls within a target range.

A heat pump apparatus includes a refrigerant circuit and a heat medium circuit. The refrigerant circuit performs a first operation using a load-side heat exchanger as a condenser, and a second operation using the load-side heat exchanger as an evaporator. A suction pipe provided between a refrigerant flow switching valve and a compressor has a container. To the heat medium circuit, an overpressure protection relief valve and a refrigerant leakage detector are connected. When leakage of refrigerant into the heat medium circuit is detected, the refrigerant flow switching valve is switched to a second state, an expansion device is set to a closed state, and the compressor is operated. When a requirement for ending the operation of the compressor is satisfied after the leakage is detected, the compressor is stopped, and the refrigerant flow switching valve is switched to a first state.

The present invention has an object to provide a refrigeration cycle apparatus. A refrigeration cycle apparatus according to the present invention includes: a compressor; and a control apparatus configured to calculate a rotation number command of the compressor. The control apparatus includes a capacity controller configured to calculate the rotation number of the compressor as a capacity rotation number, a protection controller configured to calculate the rotation number of the compressor as a protection rotation number and a rotation number selection unit configured to select any one of the capacity rotation number and the protection rotation number as the rotation number command of the compressor. The rotation number command of the compressor is calculated so that at least any one of causing the current capacity value to approach the capacity target value and causing the protection variable to approach the protection target value is satisfied.