System and method for distinguishing hvac system faults

A method of operating a heating, ventilation and air conditioning (HVAC) system, the method comprising:

• storing measurements of a liquid-side property over an initial period of time, wherein the liquid-side property comprises at least one of a liquid-side temperature or a liquid-side pressure and is associated with refrigerant provided from an outlet of a compressor of the HVAC system;
• detecting that a shutoff switch is tripped at a first time stamp corresponding to an end of the initial period of time, wherein the shutoff switch is configured to be tripped and automatically stop operation of the compressor and a blower of the HVAC system in response to determining that a suction-side property is less than a predefined minimum value, wherein the suction-side property comprises at least one of a suction-side temperature or a suction-side pressure and is associated with the refrigerant provided to an inlet of the compressor;
• accessing the measurements of the liquid-side property;
• determining, based on the measurements of the liquid-side property, that the liquid-side property has an increasing trend;
• and
• in response to determining that the liquid-side property has the increasing trend, determining that a blockage of a refrigerant conduit subsystem of the HVAC system caused the shutoff switch to trip.

A controller of heating, ventilation and air conditioning (HVAC) system, the controller comprising:

• an input/output interface communicatively coupled to:
• a shutoff switch configured to be tripped and automatically stop operation of a compressor and a blower of the HVAC system in response to determining that a suction-side property is less than a predefined minimum value, wherein the suction-side property comprises at least one of a suction-side temperature or a suction-side pressure and is associated with refrigerant provided to an inlet of the compressor;
• and
• a liquid-side sensor positioned and configured to measure a liquid-side property, wherein the liquid-side property comprises at least one of a liquid-side temperature or a liquid-side pressure and is associated with the refrigerant provided from an outlet of the compressor;
• and
• a processor, coupled to the input/output interface, the processor configured to:
• store measurements of the liquid-side property over an initial period of time;
• detect that the shutoff switch is tripped at a first time stamp corresponding to an end of the initial period of time;
• access the measurements of the liquid-side property;
• determine, based on the measurements of the liquid-side property, that the liquid-side property has an increasing trend;
• and
• in response to determining that the liquid-side property has the increasing trend, determine that a blockage of a refrigerant conduit subsystem of the HVAC system caused the shutoff switch to trip.