The Tranquility® 24 (SY) Compact Two-Stage Series comes with all the reliability features for which the Tranquility Series is known. They include superb efficiency ratings, quiet operation, and application flexibility. Tranquility SY surpasses ASHRAE 90.1 efficiency standards and uses R-454B, a low Global Warming Potential (GWP) refrigerant, setting a high standard for eco-friendly performance.