Does there exists equipment, ductwork and controls to simultaneously run a gas furnace and heat pump?
I have a 10yr old gas furnace for main level plus a 1.5T heat pump for a sun room. The heat pump compressor has gone bad so am looking to upgrade. I would like to have a single larger higher efficient heat pump installed to handle both the main level and sun room. Given the loading differences, I would like to have these areas zoned with dampers. I would also like the heat pump to be a multi-stage so when only the sun room is calling for air, a lower output can be selected and the damper to the main level closed off.
To add complexity (I like complexity), I would like my existing single stage furnace to be retrofitted with a modulating burner and coupled with the new heat pump so that they can be run simultaneously to supply both zones in the heating season. The load would be split between the two sources such that optimal efficiency is achieved subject to the constraint that supply register air temperatures always be in that toasty 110F gas furnace range during heating at ALL outside temperatures.
I understand about corroding furnace heat exchangers when placed downstream of a heat pump A-coil. Hence I am asking if there exists a sound engineering solution that runs the heat pump and furnace air through separate plenums to be mixed downstream via dampers? I would imagine this would require a control system that can vary blower speeds, dampers, heat pump stages, and burners such that temperatures, pressures and flows all stay within correct ranges.
1.) Has anyone designed such a beast for a residential home owner?
2.) Forgetting about cost and complexity, are there any other technical hurdles to such a design?