Patent ID: 8590330

Claim:
A method of operating a transport refrigeration unit that is operable to regulate a temperature of a cargo space, the method comprising: providing a controller; driving a refrigerant compressor of the transport refrigeration unit with an internal combustion engine to compress a refrigerant defining an engine operating state of the transport refrigeration unit; driving the refrigerant compressor of the transport refrigeration unit with an electric motor to compress the refrigerant defining a motor operating state of the transport refrigeration unit; sensing the temperature of the cargo space; receiving into the controller a signal indicative of the temperature of the cargo space; determining the temperature of the cargo space using the controller; and switching from the engine operating state to the motor operating state in response to a signal generated by the controller when the controller determines that the temperature of the cargo space is less than or equal to a first predetermined temperature and greater than or equal to a second predetermined temperature less than the first predetermined temperature.