I have been researching a new closed-loop geo system for my home and this forum has been very educational. Now I hope others are able to help me with a couple of key decisions.
I have bids from three suppliers that I am considering, and would appreciate input from impartial experts. The basics:
- I am located in St. Paul, MN so heating will be a bigger concern that cooling
- My home is 16 years old, 5,200 sq. ft with lots of southern facing glass and is very tight and well insulated. Recent energy audit with infrared and leak test confirmed this
- I am replacing a 92% gas furnace (bad heat exchanger) and power vent gas water heater
- Two suppliers performed a manual J calculation from plans and determined that the heating load is estimated at 72,000 Btu/hr, cooling is 42,000 Btu/Hr. Based upon an analysis of my utility bills, these numbers seem about 15% high from my actual experience.
- I have a 40,000 Btu sealed combustion gas fireplace on a thermostat that will remain in the house which may be a consideration for aux. heat
- All suppliers have recommended a 5-ton unit for my application.
My first question is should I go with an integrated unit with electric aux. heat, or a split system with a new 95% gas furnace? It turns out that with rebates and all of the different electric rates involved, the purchase price and operating costs are about the same for either solution, so I can choose which is most appealing. Looking for feedback on the pros and cons of each from those in the know who do not have a financial interest in the decision.
Second question, there is a significant difference in the design parameter of minimum EWT that the suppliers are proposing – one is using 25F where others are using 30-32F. As expected, the supplier that is using 25 is proposing a shorter loop field and a lower price, but I am concerned that the system will not perform properly in the dead of winter. What is an appropriate design min. EWT for a cold climate like Minnesota?
Lastly, I am considering equipment from Carrier/Climate Master, WaterFurnace and Hydron Module. If there are thoughts on which is more appropriate for my climate, please speak up.
Any help would be appreciated. If I missed any key parameters that need to be considered, please let me know.
Thanks!
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