Outdoor unit of air-conditioning apparatus

An outdoor unit of an air-conditioning apparatus comprising:

• a compressor configured to compress refrigerant;
• a heat exchanger through which refrigerant sent out from the compressor flows;
• a flow switching device configured to switch flow directions of refrigerant;
• a casing that houses the compressor, the heat exchanger, and the flow switching device;
• a bottom plate heater provided to a bottom plate of the casing and configured to heat water that falls from the heat exchanger;
• and
• a controller configured to control the compressor and the flow switching device and to perform a heating operation and a defrost operation in which frost that attaches to the heat exchanger during a heating operation is removed,
• the controller being configured to control the bottom plate heater according to outdoor air temperature and outdoor air humidity during the heating operation and the defrost operation,
• in a case where the controller determines that outdoor air is at low temperature and at low humidity and a temperature difference in outdoor air after the heating operation starts is lower than a preset threshold value, the controller being configured not to operate the bottom plate heater during the heating operation and to operate the bottom plate heater only during the defrost operation.

An outdoor unit of an air-conditioning apparatus comprising:

• a compressor configured to compress refrigerant;
• a heat exchanger through which refrigerant sent out from the compressor flows;
• a flow switching device configured to switch flow directions of refrigerant;
• a casing that houses the compressor, the heat exchanger, and the flow switching device;
• a bottom plate heater provided to a bottom plate of the casing and configured to heat water that falls from the heat exchanger;
• and
• a controller configured to control the compressor and the flow switching device and to perform a heating operation and a defrost operation in which frost that attaches to the heat exchanger during a heating operation is removed,
• the controller being configured to control the bottom plate heater according to outdoor air temperature and outdoor air humidity during the heating operation and the defrost operation,
• the controller being configured to operate the bottom plate heater during the defrost operation, to operate the bottom plate heater during the heating operation in a case where the controller determines that outdoor air is lower than a first control temperature and higher than or equal to a second control temperature, which is lower than the first temperature, and to stop the bottom plate heater during the heating operation in a case where the controller determines that the outdoor air is lower than the second control temperature and at low humidity.