A heat pump system includes a heat exchanger coil and a heater configured to transfer heat to the heat exchanger coil. The heat pump system also includes a controller communicatively coupled to the heater. The controller is configured to activate the heater in response to determining that a detected temperature of the heat exchanger coil is below a threshold temperature for a threshold time period.

A refrigerating and air-conditioning system includes a plurality of independent refrigerating and air-conditioning apparatuses each including a refrigerant circuit and a defrosting unit, and further includes a system controller managing the apparatuses in an integrative manner. The system controller includes a defrosting operation control unit. When a time interval between an estimated defrosting start time calculated for a given refrigerating and air-conditioning apparatus and a subsequent estimated defrosting start time calculated for another refrigerating and air-conditioning apparatus is less than or equal to a predetermined target start time interval, the defrosting operation control unit transmits a defrosting start instruction signal to the defrosting unit of the given refrigerating and air-conditioning apparatus.

A heat pump device includes an air conditioning control device configured to switch the heat pump device among a plurality of operation modes including an air-heating operation mode in which an indoor heat exchanger serves as a radiator and an outdoor heat exchanger serves as a heat absorber, and an air-cooling operation mode in which the indoor heat exchanger serves as a heat absorber and the outdoor heat exchanger serves as a radiator. The air conditioning control device switch a refrigerant pipe such that refrigerant is, in the air-cooling operation mode, supplied to part of the outdoor heat exchanger serving as a refrigerant inlet in the air-heating operation mode.

Methods, devices, and systems for frost management of an evaporator are described herein. One device includes a memory, and a processor configured to execute executable instructions stored in the memory to receive operating information of a heat pump, determine a first set point of at least one of a number of components of the heat pump and a first operating temperature, receive a second operating temperature of the evaporator that is positively offset from the first operating temperature of the evaporator, determine a second set point of at least one of the number of components of the heat pump based on the second operating temperature, and modify a set point of at least one of the number of components of the heat pump to the second set point such that a heating mode of the heat pump is enabled for a heating interval length of the heat pump.

An outdoor unit control unit 200 has a defrosting operation condition table 300a that defines a defrosting operation interval time Tm in accordance with a total sum of rated capacity of indoor units 5a to 5c and a refrigerant pipe length as lengths of a liquid pipe 8 and a gas pipe 9. The outdoor unit control unit 200 uses the total sum of the rated capacity of indoor units 5a to 5c input by using an installation information input unit 250 and refers to the defrosting operation condition table 300a, so as to determine the defrosting operation interval time Tm. Then, the outdoor unit control unit 200 forcibly performs a defrosting operation when the defrosting operation interval time Tm elapses without establishment of a defrosting operation start condition since the last defrosting operation is terminated.

If an exterior heat exchanger is sensed to be frosted while a heat pump device is operating in a first heating operation mode in which two interior heat exchangers are used, the operation modes are switched into a second heating operation mode in which one interior heat exchanger is used, and then switched into a defrosting operation mode.

A method is disclosed or detecting a frozen evaporator coil of a refrigerant vapor compression system for supplying conditioned air to a temperature controlled space before ice build-up on the evaporator coil becomes so excessive as to result in an undesirable on-off cycling of the refrigerant vapor compression system compressor when operating to a frozen temperature maintenance mode. The method may also include initiating a defrost of a frozen evaporator coil of the refrigerant vapor compression system before ice build-up on the evaporator coil becomes so excessive as to result in an on-off cycling of the refrigerant vapor compression system compressor when operating to a frozen temperature maintenance mode.

A heat pump device includes an air conditioning control device configured to switch the heat pump device among a plurality of operation modes including an air-heating operation mode in which an indoor heat exchanger serves as a radiator and an outdoor heat exchanger serves as a heat absorber, and an air-cooling operation mode in which the indoor heat exchanger serves as a heat absorber and the outdoor heat exchanger serves as a radiator. The air conditioning control device switch a refrigerant pipe such that refrigerant is, in the air-cooling operation mode, supplied to part of the outdoor heat exchanger serving as a refrigerant inlet in the air-heating operation mode.

A vehicle air conditioner which improves the frost formation judging precision of an outdoor heat exchanger, acquires the heating performance, and avoids unnecessary defrosting. A controller executes a heating mode. The controller (32) judges frost formation onto the outdoor heat exchanger (7) on the basis of a refrigerant evaporation pressure PXO of the outdoor heat exchanger (7) and a refrigerant evaporation pressure PXObase of the outdoor heat exchanger (7) during non-frost formation or on the basis of a refrigerant evaporation temperature TXO of the outdoor heat exchanger (7) and a refrigerant evaporation temperature TXObase of the outdoor heat exchanger (7) during the non-frost formation, and allows a high-temperature refrigerant gas to flow through the outdoor heat exchanger (7), thereby performing defrosting of the outdoor heat exchanger (7).

A heat pump device includes an air conditioning control device configured to switch the heat pump device among a plurality of operation modes including an air-heating operation mode in which an indoor heat exchanger serves as a radiator and an outdoor heat exchanger serves as a heat absorber, and an air-cooling operation mode in which the indoor heat exchanger serves as a heat absorber and the outdoor heat exchanger serves as a radiator. The air conditioning control device switch a refrigerant pipe such that refrigerant is, in the air-cooling operation mode, supplied to part of the outdoor heat exchanger serving as a refrigerant inlet in the air-heating operation mode.