A controller controls a first air-conditioning system and a second air-conditioning system having separate refrigerant circuits, but arranged for conditioning a common space. The controller includes a multi-variable regulator to determine control signals for controlling operations of first components of the first and the second refrigerant circuits to reduce jointly and concurrently an environmental error between setpoint and measured values of environment in the common space. The controller also includes at least two single-variable regulators to receive operational errors between setpoint and measured values of an operation of a second component of the first and the second refrigerant circuits. The controller separately determines control signals for controlling the operation of different refrigerant circuits that reduce the operational errors. The controller also includes a lookup table that stores values for other inputs of the systems that improve its performance, and which selects specific input values for both systems according to the outputs of the multi-variable and/or single variable regulators. The controller includes an electrical circuit for controlling the first and the second air-conditioning systems according to the determined control signals.

An conditioner including a compressor that compresses refrigerant, an outdoor unit fan that blows out the air heat-exchanged by an outdoor heat exchanger, a noise sensor that measures noise, a data part that saves noise data measured by the noise sensor, a control part that performs a low noise operation by distinguishing between ambient noise and noise made by the air conditioner based on noise measurements from the noise sensor, wherein the control part sets a target noise level according to the ambient noise, changes the operational settings of the compressor and outdoor unit fan, and controls the operation to ensure that the noise from the air conditioner does not exceed an environmental noise regulatory value.

A method of defrosting an indoor coil in a refrigeration system including, while the system is operating in the refrigeration mode, with a controller of the refrigeration system, determining a defrost commencement time at which the refrigeration system is to commence operating in the defrost mode. With the controller, one or more defrost energy conservation processes are initiated prior to the defrost commencement time, to decrease a rate at which thermal energy is transferred from the refrigerant in the outdoor coil to ambient air around the outdoor coil. The defrost energy conservation process continues until a defrost energy conservation termination criterion is satisfied, at which time the defrost energy conservation process is terminated. Upon termination of the defrost energy conservation process, operation of the refrigeration system in the defrost mode is commenced.

An air-conditioning apparatus includes an outdoor unit with a compressor, an outdoor heat exchange, a four-way valve for switching a refrigerant flow passage, and an outdoor flow control valve which controls the flow rate of a liquid refrigerant; and an indoor unit that includes an indoor heat exchanger, and an indoor flow control valve which reduces refrigerant pressure. A refrigerant circuit is formed by connecting the outdoor unit and at least one indoor unit by a pipe. A controller controls a component of the refrigerant circuit, based on the relationship between a first target set temperature used for temperature control of air to be conditioned and a preset second target set temperature.

An engine driven heat pump includes an outdoor fan and an engine cooling water pump, each of which is driven by the generation power of a generator, and after a lapse of a first predetermined time from a predetermined actuation time of an engine, the output power from the generator is output-controlled, and the power output control is started so as to obtain the generation power, and when it is determined that the generation voltage after the start of the power output control is equal to or higher than a predetermined voltage, the engine cooling water pump is driven, and after a lapse of a second predetermined time from a predetermined drive time of the engine cooling water pump, the outdoor fan is driven, and after a lapse of a third predetermined time from a predetermined drive time of the outdoor fan, the output control of the inverter is started.

A heat pump including a housing configured to be disposed outdoors; a compressor that compresses a refrigerant; a fluid refrigerant heat exchanger configured to perform heat exchange between the refrigerant and a fluid; an outdoor heat exchanger configured to perform heat exchange between the refrigerant and outdoor air; a pressure sensor configured to detect a pressure of the refrigerant flowing between the compressor and the fluid refrigerant heat exchanger; a first shut-off valve disposed in a pipe connected to a discharge of the compressor; a second shut-off valve disposed between the outdoor heat exchanger and the compressor; and a controller configured to: determine whether the refrigerant leaks, control the first shut-off valve to be closed, when the refrigerant leaks, and control the second shutoff valve to be closed, when the pressure sensed by the pressure sensor is less than a predetermined reference pressure.

An air-conditioning device which melts a large amount of frost deposited thereon while maintaining the proper operation of a compressor by setting the defrosting operation time according to the low pressure of the compressor. This air-conditioning device has: a refrigerant circuit which has a compressor, a refrigerant flow path switching device, a heat-source-side heat exchanger, a throttle device, and a use-side heat exchanger being connected by refrigerant pipes, and configures a refrigeration cycle; a pressure sensor which detects the pressure on the intake side of the compressor; and a control device which, during defrosting operation, controls the refrigerant flow path switching device and supplies the compressed refrigerant from the compressor to the heat-source-side heat exchanger, compares the detection value of the compressor sensor and a first threshold value, and changes defrosting operation time on the basis of the comparison result.

An air conditioner includes a compressor; an outdoor heat exchanger; an indoor heat exchanger; an outdoor fan configured to supply outdoor air to the outdoor heat exchanger; and an indoor fan configured to supply indoor air to the indoor heat exchanger. The air conditioner performs a heating operation by driving both the indoor fan and the outdoor fan and by causing refrigerant to flow in one direction through both the indoor heat exchanger and the outdoor heat exchanger and so that a defrost operation in which both the indoor fan and the outdoor fan are stopped is performed by causing the refrigerant to flow in the opposite direction to that in the heating operation. When a defrost failure is caused by the defrost operation the outdoor fan is driven, and the indoor fan is stopped for a predetermined period of time, after which the defrost operation is resumed.

A system and method are described that help to alleviate pressure and strain spikes in and around dead tubes or frontiers between stages in a multi-stage condenser coil. Instead of cycling a fan off and on, fans associated with the condenser are kept running at a low speed instead of being turned off. Preventing the fans from turning off completely helps to even out the pressure and strain spikes. The present teachings can be especially beneficial in aluminum-based coils. The present teachings include both a unit controller that carries out the teachings, and a system based on temperature and/or pressure switches connected to a fan controller.

An air conditioner and a method of controlling an air conditioner are provided. The air conditioner may include a compressor, an accumulator that recovers a liquid refrigerant contained in a refrigerant flowing into the compressor, an outdoor heat exchanger that performs heat exchange of air using the refrigerant, an outdoor unit fan that supplies outside air to the outdoor heat exchanger and discharges heat-exchanged air, a refrigerant charging pipe connected to a refrigerant pipe and allowing the refrigerant to the additionally introduced from the outside, a refrigerant charging valve installed in the refrigerant sharping pipe to open and close the refrigerant charging pipe, and a controller that sets an operation mode so as to operate in a cooling operation or a heating operation upon setting of a refrigerant charging mode, sets an operation frequency of the compressor in accordance with a load of an indoor unit upon the setting of the refrigerant charging mode to allow the compressor to operate at the set operation frequency during the refrigerant charging, and calculates an amount of refrigerant in order to stop the refrigerant charging when a predetermined reference value is reached.