Methodology for adjusting residential cooling and heating seasonal performance ratings to exclude supply fan energy

Abstract

This article presents new models to convert the rated cooling and heating seasonal performance efficiency (i.e., SEER or heating seasonal performance factor) to steady-state efficiency rating (i.e., energy efficiency ratio or coefficient of performance) that do not include supply fan energy to be used in building energy simulations for the units less than 19,000 W (65,000 Btu/hr). A review of the two existing conversion equations found that the existing methods do not adequately reflect the characteristics of the units currently available on the market (i.e., units higher than SEER 13/heating seasonal performance factor 7.7) that comply with the provision of the National Appliance Energy Conservation Act of 2006. This analysis was performed using the two new datasets from the California Energy Commission database and the 2012 AHRI directory as well as the AHRI fan performance data collected from several manufacturers. The developed models were adopted in the new edition of ASHRAE Standard 90.1-2013: Energy Cost Budget Method (Section 11) and Performance Rating Method (Appendix G), which is expected to be used in building energy simulations, especially at the design stage. These improved models will allow a more accurate calculation of the impact of the HVAC system efficiency on building energy use compared to the two existing conversion equations, which are discussed in this article. The impact of using the new models on building energy simulation was studied using a 2009 IECC code-compliant, 232-m2 (2500-ft2) house varying the air conditioners SEER and heating seasonal performance factor ratings.