I'm in the home stretch of designing this project (yes, I'm a little slow on it). I have 4 distinct designs that I've settled on (that will find use beyond just this project).
My "best" design is the waterfurnace Synergy3D (actually branded as american standard) unit to provide both the forced air and hydronic side of the equation. The place I'm getting hung up is the domestic hot water production (still). When I'm supplying the hydronic side of things I'm also including the garage floor heat (currently supplied by a separate water heater). That bring my heat pump size up to 4 ton from 3 tons. Air conditioning is still OK, my first stage cooling doesn't exceed the calculated load, but I can't go any higher than 4 tons.
That being said, I would still really like to offer Geo-heated domestic as an option, but it's looking like I would either be on electric backup heat (if setting the hydronic side to priority) or won't be able to keep up with the domestic load (if leaving the air side as priority).
The plan is to use a Triangle Tube SME Multi Energy tank that has 100 gallons of primary boiler/hydronic water surrounding a 60 gallon inner tank of domestic hot water. The Geo unit would be tasked with keeping the water in the inner tank at 120 degrees so the outside water should be also at 120 degrees when everything is said and done. Radiant floors would draw from the 100 gallons of primary water and the desuperheater would also temper a preheat buffer tank (mostly for summer benefit as the Geo will be supplying the heat in cold months anyways.).
Am I making this too difficult? Am I chasing that last dollar of savings but adding a lot of cost and potential disappointment? Should I just KISS and put in an instantaneous Hot water heater behind a buffer tank and call it a day? I'm looking for a sanity check here and hoping you guys can set me straight.