I have just received bids from 2 contractors to replace my HVAC system. The Lennox rep sized the replacement gas furnace at 88000btu and the Trane rep sized his replacement at 80000btu. Both furnaces are 2-stage variable speed 80% efficiency. My old system is 100000btu but is only about 65% efficient. I understand that my old system only delivered 65000btu. If the Lennox @ 88000 btu is 80% then I will get 72,400btu and the Trane will get me 64000btu. I am concerned because the Trane is actually 1000btu less than the old system. The house is a 1500sq.ft. ranch with a walk-out basement that has been finished after the original house was built. This means additional supplies were added to the trunk after the original system was installed. Am I correct in being concerned? Should I discuss bumping-up the Trane from 80000btu to 100000btu or should I expect the newer 2-stage system to handle this.
I realize many will ask why only going for a 80% replacement. It is due to the location of the furnace from exterior walls and the need to tear down drywalled ceiling to install a 90+ unit.
Thanks for assistance.