Apparatus and method for detecting faults and providing diagnostics in vapor compression cycle equipment

A method of providing diagnostics of a refrigeration system, the refrigeration system including a compressor, a condenser, an expansion device, and an evaporator connected together, the method comprising:

• determining the type of expansion device used in the refrigeration system;
• storing a plurality of HVAC system parameters that have been pre-defined for a particular refrigeration system and type of expansion device used;
• defining a plurality of diagnostic messages based on said particular refrigeration system;
• measuring at least five but not more than nine HVAC system variables;
• calculating various HVAC operational variables including superheat based on the measurement of said at least five HVAC system variables;
• comparing the calculated HVAC operational variables to said stored HVAC system parameters;
• and
• conveying at least one of said plurality of diagnostic messages to a person performing said diagnostics;
• wherein if it is determined during said determining step that said expansion device is a thermal expansion valve, the superheat is fixed at 20 ° F.