We have decided to replace our Central Air Unit (Chrysler AirTemp), A-Coil (Chrysler), and Gas Furnace (old). We have had 2 Carrier installers out to estimate our needs and are looking at the Infinity Line of products (38TDB A/C and 58MVP furnace). FYI we are located outside of Philly, 2 story colonial, ~2500 sq ft.
So Installer #1 came and did a complete walkthrough of the house, noting all vent locations, taking measurements of our existing duct work, etc. He provided a cooling load estimate of 40000 Btuh and heating load estimate of 80000 Btuh, using a Manual-J calculation (excuse my ignorance if this is not the correct "lingo").
Installer #2 came and looked at our exterior A/C unit and our interior furnace, took no measurements nor looked at our existing vents. He provided no cooling or heating load estimates in his write-up.
Here are what the 2 recommended:
Installer #1: 58MVP-080 (80000 Btuh), 38TDB-048 (48000 Btuh)
Installer #2: 58MVP-100 (100000 Btuh), 38TDB-036 (36000 Btuh)
Now, Installer #2 did mention that he likes to "go one size bigger" on the 2-stage furnaces so that only in extreme weather situations will the furnace move to the higher speed.
Installer #1 offers a 10 year parts/labor warranty versus 5 year part/labor for Installer #2. If I assume that cost difference is ~$500 and that the difference in combined equipment prices is ~$700 (I think the +/- price in equipment works out to the Installer #1 equipment being more expensive), there is only about a $220 difference in price between the 2 Installers.
I am looking for some advice on the proposed systems and the logic behind Installer #2's choice of furnace. Also, is the 10 year parts/labor that important?