If you second floor is not cooling, you most likely have a poor cold air return on the second floor. Increasing the condenser size will make the condition worse. You must return 60% of the air, in a 2-story home, near the ceiling on the second floor. Hot air will float on the cold air. Without a process to remove the warm air from the ceiling the cold air will stay in the first floor. If you can feel your head getting hot as you climb the stairs and air is comming from the vents, it's the return. Poor air flow is common place in new construction homes. New construction homes are sized for A/C using the worse case sonero. Front facing SW because that is where the summer heat comes from and most of the windows are. Winter time loads are based upon the front facing NE. Now, every home in the development will get that HVAC package plus a little for Grandma.( 1/2 ton to a ton extra and twice the number of Btu's in the furnace) Why? Because neighbors will compare sizes and the developer does not want to explain to the customer about Manual J, if he even knows what it is. A good load calc program will allow you to rotate the building and see how the direction the home faces changes the load. SEER tells you how efficiently the equipment converts electric to cooling. Btu/$. 13-SEER will give 13,000 Btu/ kW. 15-SEER= 15,000 Btu/kW. etc. If you think a larger A/C unit is better, you are mistaken. A properly sized unit will yeil a home with lower humidity and more comfortable. If the home needs 2-/2 tons and 5 tons is installed, cooling costs will be the same if identical SEER units are installed. the 5 ton unit will run 1/2 the time amd the house will be more humid. Remember, SEER= Btu/$. so operating costs will be the same, you will not be as comfortable and your wallet will be lighter than it should. The internet is a good way to find out about contractors and a poor way to size an air conditioner. Find a responsible contractor, have him do a Manual J (heat load) and go with his recommendations. Do not pay attention to what the guy next door has. He may have a friend that knows a guy that installs A/C. Run like a deer from that guy. You may get a good price but no comfort. BIGGER IS NOT BETTER. When it comes to air conditioning.

Thanks, tigerdunes. This is Weston's wife now, but we've both been researching this. I agree that the pricing seems good from what we've researched. We read about the noise, but is it only 3 decibels? We all leave our A/C on 24/7 so outside noise isn't that big of a deal with OUR unit (it's our neighbor's we'd like to quiet - it's closer to our living space). We also saw that we didn't want the XL 16i. We talked to the salesperson again today and he said he COULD quote us on an XL, but it would be 1500-2000 add'l per unit, and it just seems silly. Our old units are 10 SEER, so we should already see a big change. The thermostat is the XL-600, which DH is not too pleased about. We asked the sales guy about the 900 and he said it would only work with the XL 19i and XL 20i. I think he MEANT to say (ahem) that they throw those in with those more expensive systems. What should we offer him to upgrade, and are you sure it would work? What benefits are there w/900 over 600? BTW, we are not new to programmable thermostats - have had them in two houses for >10 years. We do turn on heat sometimes - ranges from 2-30 days a year. Now I guess we need to call the salesman again and ask if we get heat with this?! Surely that would be included in the quote, but now you've got me wondering. I know we're weird animals down here to not ask about a heater! ;-) Thanks so much for your help!

I got a quote last week from a Trane dealer in Southern California and they still carry the XR13. Maybe it depends on where you live. The XR13 can get you up to 14 SEER with the correct coil and furnace. 14 SEER is about 5% more efficient than 13 SEER according to the Trane brochure (see photo). Depending on your electric cost to run the a/c in your house, you could save about $20 per year (say your electric bill for a/c is $100 a month, 5% savings is $5/month, run a/c 4 months = $20/year). This is just my guesstimate. So, it may take 10 years to get your money back to pay for the $2k extra for furnace. I would go for option #1...just replace the condenser and get a new matching coil. When the furnace goes out, then get a more efficient furnace. Now, if you want to go to SEER 16, then you need to replace more equipment and maybe ducts/registers.

On the surface, that sounds like a deal....but...hummm....I would want to see all model numbers and price...furnace, condenser, Trane evap coil-no substitute...on the furnace, I assume the 100 K XV80 to get the 5 ton blower...you do want a pleated filter media cabinet...see what dealer recommends on thermostat...I would want HW Prestige 2.0 for furnace staging and DOD feature...if you are getting good pricing, I would ask about upgrade pricing to XR16 and 2 stage XR17... IMO