First of all let me say that I am so happy that this group was established for people like me. I am new to Geothermal and have a question I need some advice on. We bought a house last November with an Open Loop System that works off a well. The unit is a 3 ton Bosch system. We have a 1800 square foot brick house that has 900 up and 900 in the basement. The basement is fully exposed on the North side (sliding glass doors on the entire side), the other 3 walls are underground. We are doing an addition upstairs adding another 900 square feet. Once this addition is done we will only use the basement a few times a year for company. What we are wanting to do is put in a different HVAC upstairs that would cover the original 900 sq ft upstairs and the additional 900 sq ft we are adding. I understand that the system would really be oversized for 900 sq.ft. But, my question is, can we run that Geothermal System on just the 900 sq feet in the basement without hurting the equipment. Like I said earlier it would maybe be ran 2-3 days a month max. If that would not be feasible do you think the current unit would carry the additional 900 sq ft we are adding. Taking into consideration that a third of the square footage is in the basement and not used year round. Heating /Cooling: 900 sq.ft Unit: Bosch Size: 3 ton Location: Milledgeville, Ga.