Well after replacing the limit switch it still tripped , he also removed the ducting to prove to me it wasn't a restrictive venting issue . The service tech believes it is a burner issue . I spoke to the owner of the outfit he promises complete satisfaction , they are replacing the furnace and will re-evaluate the sizing . If I want a different thermostat (tech felt that the thermostat was a good one) , they will also get whatever I want (any recommendations?) It seems to be being handled as professionally possible . Except for possibly having the wrong size furnace. They will advise me on Monday the details . Trane is being called by the company.
Where are you? What's the house like? More than normal amount of windows? No insulation? I'm with been, still suspicious on sizing.
As I pointed out, Sis has a 75K 92% on a 2 story house about your size. Ducts in the crawl, leaky windows, decent insulation. At about -5° it will run constantly, might start to lose ground about -10° out but that's once every 10 years or so. She got a test furnace - I had a choice of 75K or 120K and wasn't about to go the monster.
I would certainly request the 2 stage thermostat wired properly instead of crippling a great furnace with a timed 2nd stage.