I have two Carrier Infinity furnaces and AC condensers in my 2 story house. The condensers are 2-stage units. The first floor condenser is 2 tons, the second floor is 3 tons. I have used them for 4 summers so far. I set the temperature at 78-79 degrees. I find this comfortable since the humidity is usually in the 35-40% range. They do an excellent job of humidity control. In the low stage the air flow is low and very quiet. There are no cold drafts coming from the vents. It is very comfortable. There is another reason why a 2-stage AC has an advantage over a single stage unit. Let's say your heat load calculation was 2.3 tons. If you got a single stage unit, the correct size would be 2.5 tons. But if you got a 2-stage unit, you would have to get 3 tons. This sounds wasteful since the low stage has a capacity of about 2 tons. When would the AC ever go to the second stage? Here are two scenarios. I set back my upper floor during the day to 82 degrees. On a typical day no one is on the upper floor, so there is no need to keep it cool. All the cool air remains on the first floor. At 7pm when the sun is going down, the thermostat calls for 79 degrees. The AC will go into the second stage to cool down the upper floor. It cools down fairly quickly since the sun is not beating down on the attic. The extra capacity helps in this situation. Let's say you have planned a big gathering at your house for a 4th of July celebration. It turns out it is one of the hottest days of the years. Your guests decide it is too hot to sit outside and decide to move into your house to escape the heat. You have a lot of people plus your are cooking some items indoors to keep everyone entertained. The heat load calculation the contractor did has no allowance for many hot sweaty people and your stove and oven on at the same time. Your heat load is now much higher than 2.3 tons. The AC is struggling to cool the house. The extra capacity of a 3 ton unit comes in handy in these types of situations. You have to decide whether spending the extra money is worth it. In my situation Carrier was offering a very attractive rebate for the 2-stage Infinity AC and furnace, plus I got an additional utility rebate for having a higher SEER rating. The final price after rebates was not much more than the single stage units. I am enjoying the added comfort and efficiency of the 2-stage units.

Quote 1: Does not qualify for the tax credit, if that's what they're leading you to believe. Good outdoor unit, but it bothers me they are not including a variable speed air handler. Quote 2: This company may just have a lower overhead and overall lower prices. If your realtor has had good experience in the past, I wouldn't have a problem. But I would suggest stepping the outdoor unit up to the Amana line (subsidiary of Goodman), which is a more premium product to compare to the other units you've been quoted. In general I would avoid Goodman/Amana because I think there's better out there, but if it's what fits the space and qualifies for the tax credit, then it would be worth considering. The Carrier units that would qualify are huge physically outside. Quote 4: Sounds like they're oversizing the equipment--not a good thing. I would avoid. 800 sqft. in our area shouldn't require 2 tons, and if the old 1.5 ton did the job in the past, that's what I'd install. Also they are not informing you that if you register the units with Trane within 60 days of install, warranty should be 10 years on all parts. And yes, a humidifier should give an added sense of warmth to the air and hence allow you to set your thermostat lower.

Hi Bob, Yes, we are waiting on the prices to come back for the Duct-less installation.

The IAQ is a communicating thermostat. The thermostat sends and receives serial data over a three wire interface. It can communicate with many different devices, one of which is the Equipment Interface Module (EIM). At a minimum, you need an EIM. There are other optional devices that may be of interest, including an outdoor temperature sensor. The EIM is located wherever the air handler is located. You will hear the EIM relays click if you are next to the air handler, but you will not hear them in your living room. The thermostat itself is silent.