Using an Air to Water Heat Pump for Radiant Floor Heating
Hopefully you read our previous post on the efficiency of Air to Water Heat Pumps. If not you can find it here.
How does it work - Air to Water heat pumps (AWHP) extract heat from outdoor air and store it in a storage tank. This leaves a resource of heat we can use as needed for domestic hot water and/or space heating. The latest AWHP use CO2 as a refrigerant which allows for efficient operation down to -25 F. This is sufficient for most residential and light commercial applications. Design care needs to be taken to keep the system demand temperatures well below the tank storage temperature of 140 F.
Example: Staple Up radiant floor with required water temperatures between 130-140 F would significantly reduce the AWHP energy efficiency. We want demand temperatures to be in the 120 F or lower range.
Low temperature radiant, like concrete slabs are ideal for Air to Water Heat Pump applications because they usually require between 90-120 F. As well as the large heat mass of the slab and system volume improve HP efficiencies and reduce short cycling.
Since the tank will store water at 140 F, a mixing valve needs to be installed between it and the system.
The Heat Pump will have a maximum output at design temperature. If more heat is needed additional HP can be added.