I'm looking for help in determining the correct HVAC system size for a small house I am rennovating. I've used the HVAC-Calc program to perform the Manual J calcluations. Based on my design conditions Sensible Gain is 20,943 BTU/H, Latent Gain is 2,690 BTU/H, Total Heat Gain is 23,633 BTY/H and Total Heat Loss is 36,130 BTU/H. I've provided this information to multiple contractors and none seem interested in the heat gain/loss figures. They all want to know what size the house is and how old it is. They each have given different recommendations on sizing ranging from a 1.5 ton to 3 ton AC condensor and a 40K to 72K furnace.
I need an AC condensor that will provide at least 20,943 BTU/H Sensible capacity. Most condensor spec sheets that I can find only provide total capacity. A Rheem model I'm considering does provide Sensible capacity and a 2 ton unit has a capacity of about 16,500 BTU/H depending on the coil, a 2.5 ton unit has the capacity of about 20,500 BTU/H and a 3 ton unit has a capacity of about 24,500 BTU/H. Is a 2.5 ton the right match for my requirements?
I plan on using an 80% AFUE furance. What is the proper size furnace for my requirements? I've read the output capacity of the furnace should be about 1.25 times of the Total Heat Loss BTU/H. Is this correct? If so I would need a furnace with an output of about 45K BTU/H. At 80% AFUE a 60K BTU/H would seem to be the closest match. How much flexibility in sizing do I have. Would a 80% AFUE furnance with 66K BTU/H and 54K BTU/H output be too large?
I've found a complete Carrier package consisting of a 2.5 ton AC condensor with coil and 66K BTUH furnace that is a great price but I want to make sure it's a good match before I purchase it.