I have two contractors who've bid systems. Both did a Manual J, but they came up with different results. Both contractors reached the same conclusion on my downstairs unit, but they reached somewhat different conclusions on my upstairs unit. I can accept that to a degree, since there's a little subjectivity (aka guesswork) involved in any such evaluation. However, I now find myself in a bit of a bind.
A little background on the upstairs unit: It's currently a 2.5 ton with a condensing unit replaced in the early to mid 1980's by the previous owner. The evaporator coil is original to the house (1975 ish). In the hottest part of summer, it runs constantly and can't keep up. The new furnace will be a Trane XV95 (2-stage, variable speed) which should help keep humidity down and make things more comfortable in the summer.
Contractor A says the upstairs unit came out to 2.2 tons. Given the history of not keeping up in the heat of summer, he recommends 2.5 tons and believes (and I agree) a new system that's properly matched will perform much better in that summer peak.
Contractor B says the upstairs unit should be 2 tons. Period. He's adamant about that value, and insists that 2.5 tons would be oversized and not control humidity as well. He'll put in 2.5 if I insist, but won't accept responsibility if it's oversized and doesn't produce the desired results. He will, however, "stand behind" his 2-ton calculation (though he stopped short of saying he'd change out the condensing unit/evaporator coil without charge).
When I discussed these two quotes with by beloved wife and came to the part about downsizing from a 2.5 to 2 ton unit, She shook her head and said, "I don't think so." (She prefers cool to warm and would be happy if I built her a sewing room inside a walk-in meatlocker).
To add fuel to this fire, I'm considering a 2-stage condenser, which comes in 2-ton or 3-ton sizes. Contractor A thinks I should use a 3-ton, Contractor B thinks a 2-stage in any size is overkill for the upstairs but of course thinks that if I do a 2-stage it should be a 2-ton.
And my beloved still doesn't like the sound of 2 tons in ANY configuration. She'll go with whatever I decide... but if it doesn't provide the right level of comfort, well, you know what they say: "If Mama ain't happy, ain't nobody happy!"
Based on your experience and professional opinion, which way should I go?