I have a couple of design questions regarding return air ducts.
I am removing an oil-fired boiler/baseboard radiator system and installing a new forced-air HVAC system in a two story colonial. I have had several estimates, most suggesting two systems, 90% gas furnace with A/C for the first floor, heat pump for the second floor. For the first floor system, everyone suggests a single centrally located return duct. With a rather open floor plan, there is no magic place for this return duct without building a box and taking up desirable floor space. To further complicate the issue, the basement ceiling is only 6'-0", so ductwork hanging down is a negative. The best location seems to be at one end of the house rather than in the center. Will this upset the balance of the system enough to worry about?
The stairway to the basement is located in the center of the house and one contractor suggested placing a grill in the wall and putting the return duct in the basement (at the bottom of the stairs) and letting the return air travel down the stairs to the return duct. Is this an acceptable method for return air? Another contractor said this approach would try to suck too much air from the basement, pulling air from outside through any available crack, even though the basement is fairly tight. I do plan to condition the basement, so there will be some provision for air supply.