Air Conditioning Equipment
One of the most important aspects of the success of the PVRES home, is the ability to take advantage of all the features designed to reduce cooling loads. We used RHVAC (Elite Software) to calculate the machine size for both the standard home and the control home in Lakeland, Florida. RHVAC uses Manual J for its calculations. We entered all of the building features for either house in detail (walls, roof, glass, duct system etc.), but as a conservatism we chose an 95°F outdoor design temperature rather than the 91°F, suggested by Manual J along with a 75°F interior temperature.
The Manual J calculations suggested a cooling system of 3.88 tons for the standard home (4 tons) and 1.73 ton (2 tons) for the PVRES house. Although, the two ton system for such a large home (2,400 square feet) is highly unusual, Tim Rice of Ward's Air Conditioning in Lakeland has worked with FSEC and with Keith Ledford and John Price out of the Orlando and Tampa Trane offices to come up with a suitable system. In a related project, we have had a very good experience with Trane's XL 1400 series air conditioner.
Consequently, we were able to select the TWY024A two-ton heat pump for the project. We will use the TWE040E13 variable speed indoor air handler to provide optimum efficiency, humidity removal and quiet operation. The Seasonal Energy Efficiency Ratio (SEER) of the combination is 14.4 Btu/W; the analogous Heating Season Performance Factor (HSPF) is 8.5 Btu/W. For the standard home we will use a standard efficiency 4-ton Trane heat pump-- a TWR048C (SEER= 10.0 Btu/W; HSPF= 7.0) as shown in the bottom right photograph.