I am building my own geothermal system... I am looking at 3 ton water to air units on E-Bay and have been wondering if there is any material reason I could not put in valves on the hot water out from the heat pump in order to divert water to my radiant floor slab. would love a water to water unit but at $8,000 for a 3 ton unit I simply cannot afford it and worry about the payback even if I could. Any ideas would be appreciated. Matt

I think you could do what you are asking, but I don't think it will do what you want. The hot water out on a 3 ton water to air unit is very small capacity, about 4 MBTUh.

So your 3 ton unit will give you about 1/4 ton of hot water heat. In the mean time you are using all of the power needed to run the three ton heat pump.

What would you do with all of the warm air coming off of the heat pump?