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

A method of providing diagnostics of a refrigeration system, the method comprising:

• a) measuring liquid line refrigerant pressure (LP), suction line refrigerant pressure (SP), suction line temperature (ST), liquid line temperature (LT), and outdoor atmospheric temperature (AMB) used to cool the condenser;
• b) when the liquid pressure port is not available, measure the discharge pressure (DP), setting LP equal to DP (or accounting for the condenser pressure drop);
• c) calculating the pressure difference (PD) between the liquid pressure (LP) and the suction pressure (SP);
• d) calculating the condensing temperature (CT) as the saturated temperature at the liquid line pressure (LP);
• e) calculating liquid line subcooling (SC) using the liquid line temperature (LT) and the condensing temperature (CT);
• f) calculating condensing temperature over ambient (CTOA) using CT and AMB;
• g) calculating evaporating temperature (ET) as the saturated temperature at the suction pressure (SP);
• h) calculating suction line superheat (SH) using suction line temperature (ST) and pressure (SP);
• i) determining the presence of a fault and, if so, a consequent diagnostics of the refrigeration system based on operating limits for at least one of the following parameters:
• pressure difference (PD), evaporating temperature (ET), suction line superheat (SH), liquid line subcooling (SC), condenser temperature over ambient (CTOA).