Current setup: 4,300 sqft 2-level ranch built in 2000 Southwest of Minneapolis. Walls R-21 Ceiling R-50 600 sqft windows double glazed, Low-E Econair 6-ton geothermal, ground source horizontal loop field installed when house was built. Supplies heat/cool for main and lower level. No desuperheater, no auxiliary heat, constant speed for fan, compressor and pump-pack. COP 3.3 Combi-core natural gas hot water heater 72 gallon, also provides in-floor heat for all lower level spaces and master bath main level. (same age as house) Aprilaire duct mounted humidifier VanE heat recovery ventilator. Natural Gas rate looks to be between $0.53 - $0.75 (not including delivery charges and taxes) Electric rate looks to be between $0.10 - $0.12 (not including delivery charges and taxes) Issues: System has been working fine (for about 18 years) until last winter - polar vortex - where it struggled a little bit only during that time. Every other year the system worked fine - we have no auxiliary heat. We didn’t think much about it struggling, just figured it was a tough winter. Come this summer, the unit seemed to be running constantly. Service call found compressor low on R-22. Recharged and solved the problem. A couple of weeks later the same thing happened and the tech found a leak that he could fix. Recharged and all is well - but expensive service calls. No issues with water heater. Do we think the polar vortex struggles were also caused by the leak? Don’t know. The “system” has been working fine for 19 years. Since the system is almost 20-years old we thought we should research replacement now rather than wait and having to figure out what we want during a crisis. And tech calls/freon are expensive. Natural gas bill is low - February $30, electric bill is high - February $360. Electric is municipal with no off-peak or other deals. Considering: We contacted a contractor that specializes in geothermal systems. They gave us a main price and a couple of add-ons. Replace heat pump with a new 6-ton unit (GeoComfort GYT072) with desuperheater connected to hot water heater to assist hot water heater. Price before rebates was X. COP 3.8/4.4 (Full/Partial Load) Add strip heater (my term) for when unit needs help. Adds 10% of X to the price. Add back up boiler and slab coil (which I understand would provide the in-floor heat instead of the combi-core water heater) Adds 50% of X to the price. Use a combination heat pump (GeoComfort GCT072) instead of standard (which, I understand, would provide hot water, and in-floor heat), and a backup boiler, aqua stat and new humidifier. Adds 72% of X to the price. COP 3.6/4.0 (Full/Partial load) Attempting to get a second quote from another geo-thermal contractor. (There don't seem to be a lot of geothermal companies in the area.) We are trying to understand why we would think of spending 50-72% more money on a backup boiler versus just staying with a combi-core water heater for in-floor heat. I know combi-core water heaters are more expensive than traditional but I don’t think they are close to what a back up boiler and tanks would be. Though I have heard anecdotal evidence that our combi-core experience (lasting over 19 years) is not the norm. But I have also heard that a boiler is more efficient for in-floor heat. Advice?
