Identifying Efficiency Degrading Faults in Split Air Conditioning Systems

Studies estimate that as much as 50% of packaged air conditioning systems operate in faulty conditions that degrade system efficiency. Common faults include: under- and over-charged systems (too much or too little refrigerant), faulty expansions valves (stuck valves, valve hunting, poorly tuned valve controllers), and fouled evaporators and condensers. Furthermore, air conditioning systems can often be adjusted to improve efficiency while continuing to meet cooling loads (adjusting system pressures, decreasing superheat setpoints). This study presents the design of a low cost device that can non-invasively measure system operating conditions, diagnose faults, estimate potential energy savings, and provide recommendations on how the system should be adjusted or repaired. Using eight external temperature measurements, the device potentially can detect and diagnose up to ten faults commonly found in HVAC systems. Steady state temperatures are compared to threshold values obtained from literature and HVAC manufacturers to detect and determine the severity of faults and subsequent reductions in coefficient of performance. Preliminary tests reveal the potential for the device to detect and diagnose common efficiency-degrading faults in HVAC systems.