Sensitivity Analysis of Installation Faults on Heat Pump Performance

Abstract

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

Review of Residential Comfort Control Products and Opportunities

“…Researchers have shown that about 60% of heating, ventilation, and air-conditioning (HVAC) systems have installation, commissioning, and performance problems, leading to as much as a 30% increase in annual energy consumption (Lstiburek 2010;Domanski 2014). The efficient design and improved operation of HVAC systems in homes could lead to significant energy reduction.…”

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Executive SummaryBuildings consume about 40% of total energy used in the United States, and residential buildings account for more than half of the energy consumed in buildings.Researchers have shown that about 60% of heating, ventilation, and air-conditioning (HVAC) systems have installation, commissioning, and performance problems, leading to as much as a 30% increase in annual energy consumption (Lstiburek 2010;Domanski 2014). The efficient design and improved operation of HVAC systems in homes could lead to significant energy reduction.The development of commercially available sensors and control-related software in the past decade has resulted in a rapidly growing and changing HVAC control industry.

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Business Case for Nonintrusive Load Monitoring

“…Residential homes also could potentially benefit from commissioning services, which could be brought into the affordable range for households with application of NILM technology. Approximately 60 percent of HVAC systems have installation, commissioning, and performance problems, leading to as much as a 30 percent increase in annual energy consumption (Lstiburek andPettit 2010 andDomanski et al 2014). Accurate end-use load monitoring identifies malfunctioning equipment both for commissioning and retro-commissioning.…”

Building America Research-to-Market Plan

“…21 Numerous field and simulation-based studies have shown installed systems operate sub-optimally because of installation faults. 22 A majority of faults identified at start-up can be corrected, while issues related to poorly designed distribution systems are harder to correct.…”