Addition of a 3 ton geothermal heat pump system to provide both heating and cooling to a previously uncooled residence
The heat pump utilizes the earth as source/sink for heating and cooling.
The underground portion of the geothermal system consists of three, 140 foot deep, 3/4" diameter geothermal tubing loops.
The loop fluid is a propylene glycol mix, 30% by mass.
Hydronic system components include an expansion tank, an air separator, dual-unit reducing and relief valves, and two wet rotor pumps.
The heat pump unit is a two-stage unloading scroll compressor using HFC-410A refrigerant. HFC-410A is a non-ozone depleting refrigerant developed to replace the most common and broadly used HCFC R22 (now being phased-out) for comfort conditioning systems.
Cooling energy efficiency ratio (EER) at nominal conditions is 27.0 (.44 kW/ton) at part-load and 18.2 (.66 kW/ton) at full-load, significantly better than an ENERGY STAR air-cooled system with an EER of 12.0.
Coefficient of performance (COP) in heating mode is 4.5 at part-load (41F ground loop) and 4.0 at full-load (32F ground loop). This is significantly better than an ENERGY STAR furnace with a COP of 0.9.
The heat pump unit produces heat at approximately $8 per million Btus as compared to a condensing propane furnace at $24 per million Btus.
A hot water generator preheats domestic hot water using a desuperheater which recovers the rejected heat from the compressor.
The existing propane furnace was left in place as backup and for future
flexibility if utility rates change dramatically.
