Automated laboratory load-based testing and performance rating of residential cooling equipment

Abstract

In the U.S., with about 64% of primary occupied homes having unitary air conditioners, a small improvement in the energy efficiency of residential cooling equipment can lead to significant energy savings. Currently, standardized equipment energy efficiency rating is based on standard AHRI 210/240, that provides a metric for comparing the performance of different equipment. However, it is generally recognized that this approach fails to appropriately rate and credit equipment with advanced controls and variable-speed components. Contrarily, a load-based testing and rating approach is presented in this paper that can capture equipment performance with its integrated controls that is more representative of the field. In this approach, representative building sensible and latent loads are emulated in a psychrometric test facility at different indoor and outdoor test conditions utilizing a virtual building model. The indoor test room conditions are continuously adjusted to emulate the dynamic response of the virtual building to the test equipment sensible and latent cooling rates and the equipment dynamic response is measured. Moreover, an automated testing procedure is presented along with convergence criteria for measuring equipment steady-periodic performance. Climate-specific cooling seasonal performance ratings can be determined by propagating the coefficient of performance (COP) from load-based testing results through a temperature-bin method to estimate a seasonal COP (SCOP). In this work, the proposed approach was implemented to test and rate a variable-speed residential heat pump. Furthermore, the sensitivity of load-based testing results to virtual building parameters was investigated. Finally, repeatability results from the load-based testing approach are presented.