AC and Furnace Replacement
My A/C stopped cooling and was determined to have a leak (not explicitly identified - the coil was frozen and the unit had to be recharged with 5 lbs of Freon) I am looking at replacing the A/C unit and since the furnace is 16 years old, am also looking at replacing the furnace. Need assistance in determining the replacement.
AC - Trane XL1200, 2.5T
Furnace - Weathermaker 9200, 60K BTU, 90% AFEU
I received the following quotes:
AC Unit: 4TTX5030A1000B
AC Unit: 24ANB630
AC Unit: 186BNA030
Question: Contractor 1 and Contractor 2 are recommending 60,000 BTU furnace, while Contractor 3 is recommending 80,000 BTU furnace.
The Manual J computation done by one contractor indicates Heating BTU of 27K and Cooling BTU of about 24K.
Since my master bdrm has 4 registers (bedroom plus sitting area) and no return and since the door is closed during the night, we are also having an additional return installed.
Question: What factors should I consider in the selection of furnace BTU? Is 80K BTU an overkill? What precautions should I take with respect to the duct size and the return size? Will the heating CFM be too high with 80K BTU and create static pressure building in the ducting? The total number of registers in the upper level (including bathrooms) are 9 and 1 return vent.
What other factors should i consider in determining the furnace BTU size? I don't have any data on the duct leakage. It is a 24 year home.
Any assistance/analysis will be appreciated.
PS: The contractor suggesting 80K indicates that the CFM can be toned down if necessary.