We are replacing a 24-year-old furnace in a condominium that has a faulty valve. It will cost around $$$ to replace the valve and that seems unwise in a furnace this old. It is an upflow configured furnace (Train BLUI62F960B2 with a Bryant coil). It is in a mechanical closet with a water heater, and a ductless return which is facing the main living space. It is very noisy, and we are told the system is oversized. Our primary concern is noise and cost; we are trying to sell the unit but could be here awhile in this market.
I am told that an 80% efficiency unit makes the most sense due to venting issues. We are on the 2nd and 3rd floor of a three story building, new venting required for higher efficiency units seems impractical. Our square footage is around 2000, and we have some additional air volume with sloped cathedral ceilings.
One estimate I received was for a Coleman modulating 80 furnace with new coil and condenser. I liked this bid, but my concerns are two fold: the contractor specified an identical 5-ton size, while other contractors told us we didn't need such a large unit. Second, if sized correctly, I'm concerned that it will run constantly. This would make the noise factor critical. (It's one thing for a manufacturer to claim it is quiet and another for it to truly be quiet.)
A second option I am considering, but haven't priced, is a Rheem combination tankless heater and furnace. This would replace the equally old water heater, and by removing the water heater from this closet might allow us to place the return in a hallway at right angle to the living space. This would involve some duct work/drywall removal.
1) How do I find out the correct size--is a manual J calc necessary, or can i trust someone's judgment?
2) Do you think it is worth the extra cost to relocate the return (i.e. go with a tankless Rheem system) or should I just go with a modulating furnace, such as the Coleman? (The Rheem would be a two stage, I believe.)
3) Is there a way to find out the actual dBs of the blowers?
Any input would be greatly appreciated, as well as any other suggestions, or alternative equipment to consider.