I guess I'm still confused on your layout. Based on the above I believe you are saying... Lowest/1st Level - Basement - underground - 700 sq ft. 2nd Level - Ground level - 700 sq ft. 3rd Level - 1,400 sq ft. 4th Level - 1,400 sq ft. Is the above correct? If so, several questions... 1. Which levels are finished? I'm assuming the basement will not be finished or the assumption is it does not need cooling since there will only be a return & no supply. Regardless, that is a bad idea. If you have only a return & no supply & if you have a tight house, theoretically the basement will turn into a vacuum. 2. Adding up 2 levels of 1,400 sq ft & 1 level of 700 sq ft equals 3,500 sq ft, not 3,300 sq ft. Why the difference? 3. It must be a very unique house design to have a 700 sq ft ground level footprint but then supporting an area twice that large above. You can't cantilever (actually I guess you could but it would be a very expensive solution) that much so you must have additional footings & piers around the 1,400 sq ft perimeter. Can you post pictures of the house or design? 4. The "cost" of a 2 1/2 ton versus that of a 3 ton is actually quite small. A contractor may elect to "price" it much more but in a competitive market you typically would not see that much of a difference in the "price". I think the primary reason people oversize is to be sure it can cool the house to the desired temps regardless of the outside temps. He is right regarding the mold & mildew issues so you would be better off with a slightly undersized unit & live w/ a few days a year when it might not cool to 68 degrees when it is 100 degrees outside. You can play with that number with the Manual J variables to see how that changes the tonnage specifications. Personally, I used 94 degrees in my area even though we do have several days a year when it hits 100 degrees. Part of that reasoning is at night we like it around 68 degrees inside but obviously the outside temps are much lower at night. So be sure to use the desired inside temperature @ the time the outside temps are hitting their highs. In our case 75 degrees inside is fine during the day. What area of the country do you live in? 5. How much window coverage do you have? What is the U-factor of those windows? I'm actually surprised that is the Manual J was done that it does not suggest the need for larger unit for the top level. You would not input any heat gains/losses for the ceilings of the basement, the ground level, or the 3rd level (1st 1,400 sq ft level) since the areas above would be "conditioned". However, you would input the ceiling/roof heat gains/losses for the 4th level thus it should have a higher BTU gain/loss than the 3rd level. Maybe it just was not quite enough to trigger to the next size up. Ask to see the numbers & if the 3rd & 4th level are the same then there is something wrong, unless you have a lot more windows on the 3rd level than the 4th level.

Hi Tiger,Ryan and Gary Happy 4th guys. Hope you're out there partying!! The Infinity system is running just great. Its so quiet inside the house that I can barely tell its on. I am so so happy with it. Its a real sweet baby. The temperature in Sacramento has been very nice these past two weeks, just in the 80's. Its kind of weird because last month we hit the 100's. I am confident though that this baby can handle it when we go back up to the 90's and 100's. As for the ducts Ryan, the flexi is attached to metal, but I don't know if its the insulated kind. But it is very quiet. I don't hear noise from the vents. I did take a peak into my attic from the ladder and the flexi is nicely layed out, no spagetti up there. Also all direct from the airhandler and no Ys. Well i've been partying all week Gary. I love this baby. But the real big party will be in the winter when its real cold outside and my living room will actually feel warm. For me that will be the biggest test because I can't handle the cold and like it very warm in the house. My old heat pump always blew in cool air when its below 45 degrees outside. If any of you will be in the Sacramento area in the future, let me know and we'll have an Infinity party or we can party Infinityly!! You guys take care and thanks again for all your help. I'll be travelling quite a bit on the job from mid July until late September, so if you post something and I don't get back to you please know that I'm on the road. Demi

It depends on how much slop is present in the Manual J, and that often depends on the age of the house. A house built from abut 1970 on in many areas had at least some code required insulation in the walls and ceiling. Houses older than that can be very hit or miss. How was the R-value of the exterior walls determined? A small error here can often have a large impact since there are so many square feet of wall involved. Attics can be easily checked in most cases. Infiltration is often a large portion of the gain/loss, but without a blower door test can only be estimated roughly. There are a number of methods using previous year heating and cooling bills, together with degree days to further refine the calculation. Even if you have never had cooling, the losses can be determined from heating use and then used to help determine cooling.

As a long time retired HVAC contractor, my advice is to have a thorough audit of your home to determine everything that can be done to reduce the heatload. Heating & cooling costs will probably continue to rise! There are many new effective ways to greatly reduce that heat-gain, heat-loss calc. By reducing the heatload of your home, they need to get the tonnage of the equipment down as low as possible! Only 2700-sf, there are ways to minimize the effect of the 18 foot ceiling areas & reduce the tonnage requirements. The proper sizing installation & setup of the new systems is everything! Duct layout & airflow is critically important. In the relative dry Dallas climate they could go to a wet coil of 450-CFM airflow per/ton of cooling or more. The low speed setting of that air handler might work with a 2-ton condenser & an a matched larger tonnage evaporator coil. - udarrell Here is a link that might be useful: A/C System Sizing for Optimal EER & SEER Efficiency