Abstract: When an air-conditioning is started, a determination is made as to whether a power relay is run so as to keep a compressor in a power-on state. When the power relay is in the power-on state, the running current of the power relay is detected. At this point, if the current value does not reach to a predetermined value, it is determined that the compressor is stopped in an exterior unit for protection.

Abstract: A fan motor is run at minimum capability at predetermined time intervals for a certain period of time when a heating mode is set but a blowing is stopped. Thus, with air around a temperature sensor disposed between inlet openings and a heat exchanger being not affected by the heat of the heat exchanger, measurement of a room temperature is carried out by the temperature sensor.

Abstract: An inexpensive control system for a multiple-type air conditioner makes it possible to automatically and independently detect frosting and conduct defrosting control in an outdoor unit during a reverse cycle heating operation in a two-compressor, multiple-type air conditioner which has an outdoor unit equipped only with a simple ON/OFF control function and which is not provided with a signal conductor for transmitting the information on the state of an outdoor unit to an indoor unit. In this case, the operation of the outdoor unit can be determined, monitored, and controlled from the indoor unit side so as to enable proper action to be taken. The control system is provided with means for independently controlling the operation of the outdoor unit and means for determining the operation of the outdoor unit from the indoor unit side according to the state of an indoor side heat exchanger and for controlling the operation of the air conditioner.

Abstract: A defrosting control method wherein an indoor unit determines whether a drop in the temperature gradient of an indoor side heat exchanger has been caused by a heavy load protecting operation or frosting of the outdoor heat exchanger during a reverse cycle heating operation of a two-unit-type air conditioner. The defrosting control is not triggered when the heavy load protecting operation is being carried out, and the defrosting control is started when predetermined conditions are satisfied, including the temperature of the indoor heat exchanger being below a raised predetermined temperature during a heavy load protecting operating.

Abstract: When a single room unit 4 is connected to a compressor 2B of the outdoor unit 1, the room unit 4 is connected to a connection box 29 which is mounted on the outdoor unit 1. Instead, if two room units 5A and 5B must be connected to the outdoor unit 1, a connection box 37 is mounted on the back of the outdoor unit 1. The connection box 37 has branches each having valves 44A and 44B and expansion devices 43A and 43B. The two room units are connected to these branches of the connection box 37. Because of these optional connection boxes, the outdoor unit itself may be constructed in a compact form, and connection of multiple room units to the outdoor unit may be carried out conveniently and correctly in a simple manner.

Abstract: A control device of an air conditioner comprises a first controller which is installed in a room to be air-conditioned and which generates the signals for controlling an air conditioner. A second controller, which is installed in a different room from the room to be air-conditioned also generates signals for controlling the air conditioner. A main controller which receives the signals from the first controller via a first interface and receives the signals from the second controller via second interface, controls the air conditioner in accordance with the two types of signals. The first controller is designed such that once the signal for starting the air conditioning operation of the air conditioner has been sent to the first interface, the first controller sends the signal for running the air conditioner in a predetermined cycle to the first interface until the first controller transmits to the first interface the signal for stopping the operation of the air conditioner.

Abstract: An object of the present invention is to provide an air conditioner in which the feedback of liquid refrigerant to a compressor is prevented and whose refrigerating cycle is constituted with an indoor side heat exchanger, a compressor, an outdoor side heat exchanger, and a pressure reducer. The controller of the air conditioner comprises a temperature control means which performs the cooling operation for a room in controlling the start or stop of the operation of the compressor based on the change of the room temperature, a protective means which stops the operation of the compressor compulsorily independent of the operation of the temperature control means when the open air temperature becomes lower than a specified temperature, and a display means for displaying the operation of the protective means.

Abstract: In a system using a processor or microprocessor for executing a predetermined initial processing and than a main processing based on a predetermined program when a reset signal is inputted, a start processing system after cutoff of a power source of the present invention includes a read-only memory (ROM) for storing a program for executing the initial processing, a program for executing the main processing and for storing initial data, a random access memory (RAM) for storing and reading data when the main processing is executed and a backup device for keeping driving of the RAM for a predetermined time after cutoff of the power source. The program for executing the initial start program includes a program for comparing data stored at a predetermined address area of the RAM memory with data stored at a predetermined address area of the ROM and for moving the initial data stored in the ROM to the RAM when the result of comparison of the data proves different.

Abstract: A method of defrost for an outdoor side heat exchanger in a heat pump having a refrigeration circuit in which a compressor, an indoor side heat exchanger, an expansion device and the outdoor side heat exchanger are connected together so that a heat collected in the outdoor side heat exchanger is radiated from the indoor side heat exchanger and that defrosting for the outdoor side heat exchanger is started when the outdoor heat exchanger is frosted, and a temperature sensor is provided to detect a temperature of the indoor side heat exchanger, wherein the defrosting is started when the temperature detected by the temperature sensor is not higher than a first predetermined level with a downward gradient, which is calculated on the basis of the temperature, of the same temperature becoming as sharp as, or sharper than, a predetermined gradient, and the first temperature level is increased after the temperature becomes as high as a second predetermined level wherein the second level.gtoreq.the first level.

Abstract: A control device for an air conditioner can prevent an erroneous operation in the starting and ending of a test run. The control device can start the test run of the air conditioner through the operation of a switching device after electrical power is supplied to the control device, and can end the test run when the operation data is received from a remote controller.

Abstract: A method and an apparatus of automatically switching between cooling and heating of an air conditioner, has which is a first temperature higher than a desired room temperature, a second temperature which lower than the desired room temperature, a first temperature zone not less than the first temperature, and a second temperature zone not more than the second temperature. The method includes the steps of changing an operation mode from a cooling mode to a heating mode during the cooling mode when the room temperature after duration of a first time remains in the second temperature zone, and changing the operation mode from the heating mode to the cooling mode during the heating mode when the room temperature after duration of a second time remains in the first temperature zone.

Abstract: An inverter apparatus comprises a bridge circuit composed of a combination of a plurality of switching transistors and a microprocessor controlling turning on and turning off of these switching transistors. Patterns of combinations of ON and OFF states of respective switching transistors obtained based on the theory of PWM (pulse width modulation) are stored in a first ROM of microprocessor. Transition of the pattern for each range of 0.degree.-30.degree. in electrical angle is stored in a second ROM in the sequence of periods subdivided from the range. Data of the time during which the pattern to be held for each period is stored in a third ROM. The microprocessor sets the holding time data in a timer, and also outputs the ON/OFF pattern, thereby turning on or turning off of each switching transistor is controlled in accordance with the count of this timer and the ON/OFF pattern. By repeating this cycle, a switching signal which continues during one cycle of AC (range of 0.degree.-360.degree.