The air-to-water heat pump has a nominal 4-ton (48,000 Btu/hr) heat output rating. It supplies an air handler as well as a heated concrete slab. At design load conditions the air handler is rated for 20,000 Btu/hr with a supply water temperature of 120 ºF. The slab is designed to release 20,000 Btu/hr when supplied with water at 105 ºF.
To accommodate these conditions the installer decides to set up the heat pump controls for a supply temperature of 120 ºF, and use a motorized mixing valve to reduce the water temperature to the floor heating circuits.
