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.

I have the evolution thermostat and I have checked it and it says it's on high stage. In the evening when the temp is low 80's it say's it's on low stage. When the temp is 90 or above it wont's cool the house off below 76 degrees no matter what the thermostat is set on, say 73 or 74. If the tech comes and the coolant charge is full should I accept the insulation issue as the cause, if they say they can't find anything else wrong. How cool do you think a Bryant 167 should be able to cool a house if it's say 95 degrees. Is 20 degrees or 25 degrees the normal cooling ability of this unit. The reason I'm concerned is that if the service tech comes and say's it's the amount of insulation in the attic, I want to be able to know it that's the real reason, I Also how would like to know how they would check for a leak in the coolant. I appreciate everyone's input. I will post when this issue is resolved so people know this information and it's outcome. Sam

Sorry, caylos, I don't have the knowledge to compare systems. My price was for a 5 ton XL 16i, clean effects and TCON803, 16 months same as cash, $8300 after rebate. If you have time, get another quote or three. My HVAC story ends more sadly than it began! The drain line was clogged, the emergency shutoff didn't work, and so condensate from a "weep hole" slowly seeped into the drywall box and through the walls under my wood floors. By the time this nightmare is over I'll have moved out of my house for a couple weeks, and the HVAC company's insurance will have paid three times what my system cost in damages. So much for the "quality control" guy. My advice to the forum: check your drain lines and emergency shut off yourself, OFTEN. Right now there is putty blocking the weep hole, so we presume that if the drain were blocked again the water would rise to the level of the emergency shut-off. I'm rather concerned that a piece of putty is the only thing keeping my $8300 A/C system from ruining my house, again. I can't imagine this is a Trane-approved solution.

Check the NYSERDA program for rebates. Mini splits lines, drains and cables can be run in interior walls into the basement. 6 of mine are run in interior walls and one in an exterior wall. Just because HVAC is retrofitted into attics in the South and West does not mean that it is a good idea. Fur-downs or basement locations would be better. You want to keep ducts and the unit inside the house envelope if you can. Ducts leak. Outdoor supply ducts depressurize the house sucking in make-up air in random places. Outdoor return duct leaks pressurize the house blowing out air in random places. Duct leaks tend to cause random pressure differentials in different room, again, turning your HVAC blower into a power vent. I have experience living in CNY homes. I believe that many could easily be cooled with a nice combination of high wall units in bedrooms and minimally-ducted units for cooling the LR, kitchen and DR areas. If not possible for the latter, maybe ceiling cassettes or high wall units.