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Sensitivity Analysis of Installation Faults on Heat Pump Performance



Piotr A. Domanski, Hugh Henderson, William V. Payne


Numerous studies and surveys indicated that typically-installed HVAC equipment operates inefficiently and wastes considerable energy due to different installation errors (faults), e.g., improper refrigerant charge, incorrect airflow, oversized equipment, leaky ducts. This study seeks to develop an understanding of the impact of different faults on heat pump performance installed in a single-family residential house. It combines building effects, equipment effects, and climate effects in a comprehensive evaluation of the impact of installation faults on seasonal energy consumption of a heat pump through seasonal simulations of the house/heat pump system. The study found that duct leakage, refrigerant undercharge, heat pump installations with undersized ducts, low indoor airflow, and refrigerant overcharge to be most prone to cause significant performance degradation and increase of annual energy use. The effect of simultaneous faults can be additive (e.g., duct leakage and non-condensable gases), weaker (low indoor airflow and refrigerant undercharge), or stronger (duct leakage and refrigerant undercharge). Significant increase in annual energy use may be caused by lowering the thermostat in the cooling mode to improve indoor comfort in cases of excessive indoor humidity levels. A well-designed and documented survey of heat pump installations would be helpful in establishing the prevalence of different installation faults and effective practices for their elimination.
Technical Note (NIST TN) - 1848
Report Number


air conditioner, commissioning, fault detection, heat pump, installation
Created October 8, 2014, Updated November 10, 2018