The old line set (copper tubing) can be reused assuming it is the correct size of the new system. If not then it needs to be replaced. It is not the preferred method, but it is done where replacing the line set is difficult. The new refrigerant will be R410. The old refrigerant (R22) must be flushed out of the old line set otherwise you have a contamination problem. This is another reason why it is good practice to replace the line set. FYI - we can talk about prices all day long on this forum. Be warned the lowest bid usually comes with the highest risk. Finally this has been beaten to death, but let's make sure you understand the concept. You can use a 3.5 ton air handler with a 3 ton condenser. The important thing is the air flow is adjusted to the correct speed. The 3.5 ton rating is the maximum air flow, not the minimum. In turns out in this case the 3.5 ton air handler has better efficiency numbers than the 3 ton air handler. If the bigger handler can physically fit in the space, then you can use it. You have to then decide if the extra efficiency is worth the extra upfront cost of the equipment.

In my opinion, a new system is not worth a penny no matter what brand if you have duct issues. I put more into the checking ducts making sure they look good and marking down what I think can be improved if anything. Brand of equipment, manual j, whatever you name it, Checking the duct in my opinion is top priority if it is accessible. I went into 3 attics today. 2 had small issues and 1 was ok. The small issues will be fixed and the cost is minimal when the new system goes in if they choose us. I will say the Trane XR15 is a more close comparison to a goodman 16 which the XR15 cost less than the XL15i. You may want to ask about the XR15 if you are considering comparing a trane model that is a more budgeted A/C It is my opinion the most important part of buying an air conditioning system is the contractor who installs it. With that, a Professional who believes in what they sell will more than likely install it better than a company who will sell you anything that you want. I am not a big fan of companies that sell many different brands.

The biggest problem with HVAC zone systems is knowing when to choose it as a solution and when not to. Some HVAC companies it's about "sell, sell, sell" whether or not it works... there's more money in "sell, sell, sell" --- when it's only about money? So does the comment above mean I do it for free? No. If you think that you are reading things that aren't there. New construction? best to choose separate systems 9 times out of 10. In order for a zone system to work, you have to know what you are doing. Most HVAC companies staff (the techs they send you) are 20-30 year olds. How much practical experience could they possible have? It's best for HVAC zone systems to be an elegant solution. A HVAC zone system is a tool in the tool bag. Not all homes are suitable for zone systems. Some homes there is no other way, and in some cases complications to those problems will make an HVAC zone system design possibly more prone to problems. You have a problem now, do you want more problems. These decisions among others are decided "in person" --- so considering that becareful what information you decide upon from the internet. Just because it's here doesn't necessarily mean it's true. That said: Depending on equipment level chosen, how many different floors you have in your structure, how much room you have available... will all be factors that make you decide one way or another. From there it's in your best interest to pick a contractor that is skilled: especially when it comes to HVAC zone systems. (there's a lot of garbage out there.) (click to enlarge if necessary) I service the Katy, Texas area.

Thank you all for the wealth of info. Did some reading and Need some HVAC-101 here. The outside unit houses the condenser AC unit and it works with the Evaporator coil which is usually situated inside the house right? In my house, the attic has the evaporator coil and furnace. So when we buy a AC Unit, we need to match the outside unit with the evaporator coil and all my quotes had this. The furnace is separate by itself correct? Took some photos, my AC tech did show me the inside of the Evaporator coils for the upstairs and it was corroded and crumbly. Having said that, it looks like my furnace may have not been the problem at all and I automatically assumed it was bad. Regardless the recommendation was to replace the whole AC and Furnace as the Furnace was $1700 something where as If I replaced it at separate times , it would cost higher. This is what I was told. Anyway can you guys please take a look at these pictures and tell me if the furnaces look real bad? I was thinking of the following options - 1. Replace just outside AC units with the corresponding evaporator coils. 2. Replace my bad 2.5 ton AC unit and the furnace. Sounds like it would be a bad idea to use a new 14 seer RUUD AC unit with new evap coil and still keep this old Lennox Furnace? 3. Leave the furnaces alone and just replace the 2.5 ton AC unit with new evap coil. Then replace the 2 ton ac unit when it starts giving trouble and still keep the other furnace until it starts giving trouble. The cost of the furnace appears to be cheaper when replacing it with the AC unit verses replacing furnaces separately 4. Any harm installing a new AC unit and use the existing Furnace? Downstairs Furnace - Opened the lid for the other furnace..anything looks bad to you guys? Both of my furnaces had a steady "flashing red and green" together and per the specs that is "normal" operation. So sounds like I might get away with just replacing 1 AC unit and the Evap coil and to get the better pricing for furnace..just replace it along. Thoughts/Comments? Thank you all for being so patient with me.