I'm working on a retrofit residential geothermal heat pump system and would appreciate feedback from those with more experience. The house is large, about 5500 sq feet, currently with two furnaces (oil - forced hot air). It is a 1978 wood frame construction. We're located in New Hampshire. The main furnace services about 4500 sq feet, with a second unit servicing a large room over a garage. The main furnace also has central air conditioning. Air conditioning is a low priority, we only need it for a few weeks every summer. The property has had several well shafts drilled because of low water flow. The proposed well to be used is a 1000ft shaft that was abandoned because of low flow. I pulled the cap and the current static is at 16' Design proposal is to replace the AC unit in the main furnace with a 5 ton system. We'll tackle the secondary furnace in the future as funds allow. Oil will remain as a supplementary heat source in the main furnace. Proposal for the well is to place a pump at 100ft with a return at 980 feet (Standing Column) with zero bleed. I realize that a 5 ton system can't meet the total heat load in winter. We currently use 6.5 tons of pellets and 1250 gallons of oil overall. I hope that it will substantially reduce the oil usage. I also plan to increase insulation, seal air ducts etc and we are in the process of replacing windows to reduce the heat load demands. The option of a desuperheater has also been discussed. I wonder if it would be worthwhile with our low AC usage and a somewhat undersized system? Any thoughts, ideas would be greatly appreciated! - Gary
You could add the desuperheater and then turn it off if the unit was not keeping up with the heat load. Just be sure and add a preheat tank for the desuperheater.
