US Patent 7617691 Refrigeration system and method of operating the same

A refrigeration system including a compressor, condenser, valve, and refrigeration branch, all of which is in fluid communication. The refrigeration branch includes an evaporator coil. The refrigeration system further includes a case adapted to be cooled by the evaporator coil, and a system controller operable to control one or more aspects of the refrigeration system, and a subsystem controller in communication with the system controller. The subsystem controller is operable to control a subsystem having one of the compressor, condenser, valve, refrigeration branch, and case. The method of operating the refrigeration system includes at the subsystem controller, monitoring a parameter of the subsystem, comparing the monitored parameter with a parameter limit, generating an alarm when the parameter is not within the parameter limit, and communicating the alarm to the system controller.