Contractor A (the guys who put in our furnace last year) simply recommended and priced a 12 SEER, R410A 2.5 ton unit over the phone.
Contractor B recommended either a 12 or 14 SEER 2 ton unit that uses R22 refigerant. B also thought our 80,000 Btu furnace was oversized for the house and offered to adjust (i.e., lower) the air flow to keep the unit from heating the house too quickly and thus short cycling.
Contractor C recommended either a 12 or 14 SEER 2.5 ton unit that uses R410A refrigerant. When I mentioned B's recommendation, he told me that an outdoor unit using R22 would not properly match the evaporator coil we now have, that "you don't want to mix oils." He didn't seem to be concerned about the furnace being oversized.
I've read a good bit about the R410a vs. R22 debate, but my first question is, should I even consider the R22 units, given the indoor coil we have? In other words, is Contractor C right about the inadvisability of Contractor B's proposal?
Secondly, none of these contractors made a thorough load calculation before submitting a proposal (nor did Contractor A when he sized our furnace last year). However, Contractor C did offer to do the full J-Manual calculation once we accepted his bid. All other things being reasonably equal, and presuming he's right about matching the coil, I'm inclined to go with him for that reason. Is that a sound decision?
If it helps, the coil model is TXC031C4HPCO/334158L5G; furnace model is TUC080C942B8/3335XN87G. House is 1200 square feet, built in 1950, brick veneer, with cathedral ceiling over kitchen and front room, and single-pane double hung windows, located in central North Carolina.
Thanks beforehand for any advice!