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Numerous studies and surveys indicate that typically-installed HVAC equipment operate inefficiently and waste considerable energy due to different installation errors (faults) such as 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 a heat pump's seasonal energy consumption through simulations of the house/heat pump system.The study found that duct leakage, refrigerant undercharge, oversized heat pump with nominal ductwork, low indoor airflow due to undersized ductwork, and refrigerant overcharge have the most potential for causing significant performance degradation and increased annual energy consumption. The effect of simultaneous faults was found to be additive (e.g., duct leakage and non-condensable gases), little changed relative to the single fault condition (e.g., low indoor airflow and refrigerant undercharge), or well-beyond additive (duct leakage and refrigerant undercharge). A significant increase in annual energy use can be caused by lowering the thermostat in the cooling mode to improve indoor comfort in cases of excessive indoor humidity levels due to installation faults.The goal of this study was to assess the impacts that HVAC system installation faults had on equipment electricity consumption. The effect of the installation faults on occupant comfort was not the main focus of the study, and this research did not seek to quantify any impacts on indoor air quality or noise generation (e.g., airflow noise from air moving through restricted ducts). Additionally, the study does not address the effects that installation faults have on equipment reliability/robustness (number of starts/stops, etc.), maintainability (e.g., access issues), or costs of initial installation and ongoing maintenance.This publication is available free of charge from: http://dx

A Net-Zero Energy Residential Test Facility (NZERTF) has been constructed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to demonstrate that a home similar in size, aesthetics, and amenities to those in the surrounding communities can achieve net-zero energy use over the course of a year while meeting the average electricity and water use needs of a family of four in the United States. The facility incorporates renewable energy and energy efficient technologies, including an air-to-air heat pump system, a solar photovoltaic system, a solar thermal domestic hot water system, and a heat recovery ventilation system sized to meet American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) Standard 62.2-2010 ventilation requirements. The largest energy end use within the home was space conditioning, which included heat loss through the building envelope, ventilation air supplied by the heat recovery ventilator (HRV), and internal loads. While HRVs are often described as being able to save energy when compared to ventilating without heat recovery, there have been no studies using a full year of measured data that determine the thermal load and energy impacts of HRV-based ventilation on the central heating and cooling system. Over the course of a year, continuous operation of the HRV at the NZERTF resulted in an annual savings of 7 % in heat pump energy use compared with the hypothetical case of ventilating without heat recovery. The heat pump electrical use varied from an increase of 5 % in the cooling months to 36 % savings in the heating months compared with ventilation without heat recovery. The increase in the cooling months occurred when the outdoor temperature was lower than the indoor temperature, during which the availability of an economizer mode would have been beneficial. Nevertheless, the fan energy required to operate the selected HRV at the NZERTF paid for itself in the heat pump energy saved compared with ventilation without heat recovery.