18 May 2017

K.4.1.1 AHRI’s Research on Rooftop Packaged Heat Pumps

This paper provides an overview of the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) research activities on air-conditioners and heat pumps. During the past few years, AHRI conducted research projects covering low Global Warming Potential (GWP) refrigerants testing and risk assessment of mildly flammable refrigerants of packaged rooftop units (RTUs).
Several low-GWP alternative refrigerants were tested for RTUs in air-conditioning and heat pump applications and other type of heat pumps in the AHRI Low-GWP Alternative Refrigerants Evaluation Program (Low-GWP AREP). Summarized testing results are presented in this paper. Many of the tested refrigerant candidates to replace R-410A are classified as A2L according to ASHRAE Standard 34. This paper will also summarize AHRI’s study on risk assessment of RTUs using A2L flammable refrigerants. The potential ignition risks of R-32 and HFO-1234yf in RTUs during operation and servicing were analyzed. The risk scenarios include 15-ton RTU for commercial kitchen, 25-ton RTU for office building, and 5-ton packaged unit installed on the ground for office building. CFD simulation on refrigerant leaks in various situations and fault-tree analysis on the refrigerant ignition risk are summarized. The risks due to refrigerant release and ignition are far below risks of other common hazards.