Investigation of the Prevalence and Energy Impacts of Residential Comfort System Faults – Hot-Humid and Hot-Dry Climates

According to the Energy Information Administration, space heating and cooling accounted for 36% of all residential primary energy consumption in 2018, with 65% of American homes utilizing central air conditioners for space cooling. Nearly 30% of those are heat pumps that reverse the vapor compression cycle for heating. Past research has found that various design faults and installation faults such as improper refrigerant charge, improper airflow, and duct leakage are commonplace, but data quantifying the national prevalence and severity of comfort system faults, along with their effect on energy use, are varied and scarce, especially when various combinations of faults are considered. Previous simulation work informed by lab experimentation estimates that various individual and combination faults can increase space conditioning energy usage by up to 30%, which is significant considering the impact over the entire life of the system.

University of Central Florida’s study will enable a large-scale survey of comfort system installations in cooling-dominated climates to find the prevalence and severity of installation faults. A suite of tests including refrigerant charge, static pressure, duct leakage, blower fan airflow, and blower fan watt draw will be performed in 100 newly installed HVAC systems located in hot-humid and hot-dry climates. The newly devised, draft RESNET/ANSI/ACCA Standard 310 “Standard for Grading the Installation of HVAC Systems” (Standard 310) methodology will be piloted as part of the field protocol, providing feedback to stakeholders on the feasibility of the standard. The collected data will serve as the basis for a suite of faults that will be imposed individually, and in combination, in Florida Solar Energy Center’s side-by-side lab homes. These findings will be used to answer the following questions:

• What is the prevalence and severity of installation faults in the hot-humid and hot-dry climate regions, including improper airflow, improper refrigerant charge, and presence of noncondensables, duct leakage, and incorrect controls setup?
• What are the energy and comfort impacts of individual installation faults and what are the interactive effects when combined, based on monitoring of energy use and environmental parameters in side-by-side lab homes?
• How feasible is RESNET/ANSI/ACCA Standard 310 “Standard for Grading the Installation of HVAC Systems” at helping practitioners identify installation faults, and how do lab results compare with current estimates for associated impacts on the HERS Index?