First off... how much do you want to spend? Secondly, how comfortable do want to be? Thirdly, is this going to be a DIY or are you hiring a PRO? All serious questions and all require serious answers. If your budget is not a top issue, then you might want to consider a multi-zone, ductless system. Mitsubishi, Heat Controller and the like all make multiple evaporator units for single outdoor units. VERY efficient and an excellent choice for small areas, but yes--- pricey. Several unitary manufactirers do offer 1 ton split systems but you have to have space to run ductwork. If you do and that is the route you go, I agree that variable speed is a must!! Matter of fact, I would also make sure the controller has humidity controls built in.

it depends. what size are the units what age are they what is layout of the house I would be concerned with dehumidification & short cycling of units. short run times don't allow for dehumidification which is a big issue in our climate. some companies 'zone' with multiple units. tell you that if one goes out, you'll still have a cool place to go...???.. other companies zone with one unit and multiple t-stats. this is a true zoned system motorized dampers, multiple t-stats and a control board. I see existing homes with 3 units sometimes one for main part of house another for master bedroom suite & other bedrooms and quite often a seperate unit for a room over a garage. it just depends on the layout of the house the homeowner's specific needs and how many units the hvac company wants to sell you. have a few companies look at your existing hvac systems and ductwork. they should give you information you need to make a good decision. several good people on this forum will help once there is more information. do you have any model numbers? is the house all electric or gas furnaces? are the utility rates high? ionized..I just don't know what to say... do you have 3 one ton units? best of luck OP.

Thanks for the response. I don't know if the close up provides any more information on the tubing -- I can't see much beyond the fins (link here and also attached). https://dl.dropboxusercontent.com/u/6994270/P1040528.JPG I think the tech just assumed that the damage included the tubing since the system was flat (no refrigerant pressure). I didn't see him do any additional investigation. The original purchase paperwork lists it as 12 seer; I don't know much beyond that. Thanks again for the response.

The independent HVAC company that deals mainly with American Standard equipment is telling me this (will send quote via e-mail later this week): 1. Need 3.5 ton unit because new refrigerant 410A is not as cold as R-22. Also, insulation in older homes in Southern California is not good, so need stronger ac unit. 2. He says that he doesn't need to do a Manual J. His 25 years of experience says to stay with 3.5 ton unit. Also, recommends replacing evap coils and furnace. 3. Noticed that existing furnace is upright/standing rather than laying flat. He's the 2nd guy to shake his head at the way it's installed. He says it's not efficient to put a furnace upright and the evap coils on the side of the upgright furnace. 4. He doesn't work with rebates, so he doesn't want to bring outside company to test energy efficiency prior and after install. He says the extra money you spend on trying to qualify for a rebate is a waste and not worth in the long run. I told him that the Costco affiliated company will do rebates and will test. He says California is going broke and probably no money for rebates. He also said that I need a 90% efficient furnace to qualify for rebates. 5. Asked if I wanted to get the permits myself. Kept saying that city is likely to ask me to move outside condenser due to its closeness to new pool. I told him I got permits 4 years ago for pool and pool equipment and city approved the location of pool and pool equipment and a/c unit was there already. 6. Says to use existing ducts and vents/registers. Will probably use same lineset since it will outlast my lifetime. 7. This guy is the actual installer. Company is so busy, they couldn't send me the salesperson. He came from finishing an install at another house. ----------------------------------------- Costco affiliated HVAC company (www.airtro.com) will also send me quote via e-mail tonight or tomorrow. Sent the salesman who says he'll be the supervisor for the job at the start. 1. Says that I can go with 3 ton a/c unit with new evap coils. Keep lineset. Says that double-pane windows help. Says Fraser-Johnson was low end unit. Says Lennox is much better. 2. Says furnace should not be upright in attic and says it's a bad installation. Recommends new furnace. 3. Permits will cost about $200 to pull. 4. Will bring a company to test ducts/energy efficiency to qualify for best possible rebate amount(probably $1500). Can't promise, but says that's his company has not been denied a rebate yet. They will do all the paperwork. 5. Recommends new ducts and a new vent/register in kitchen. Recommends dampers in ducts to evenly distribute air. Says some existing ducts are the rigid ones and might have moved/shifted over time, so he's certain that I'm losing 30% of air. $2000 to do all new ducts. 6. Problem is he only offers Lennox Merit equipment for $7000, $2000 for ducts, $200 for permits. I'm expecting a detailed quote. He says equipment is the best in the industry. 1-year labor warranty and the standard 5-year equipment warranty on the a/c unit from Lennox. I can upgrade to Lennox Elite for $2000 more, but it's a 2-stage system that I don't want. Did not recommend anything outside of the Costco price list. 7. Showed me awards from Angie's list and local newspaper, BBB certificate, insurance coverage, etc. True salesperson. My overall impression is that the American Standard independent installer seemed to say that he's been doing this for xx years and he knows what's best for me. Don't need rebates and don't need permits. That's what it felt like, but I told him I want permits. I told him I want all American Standard equipment like the Gold SI compressor, matching coils to maximize SEER, and a compatible AS furnace at 80% efficiency. The Costco affiliated company wants to charge me for a full-system (cut-in) which includes new ducts, new registers, new equipment, etc. I think that he wants to put a new register in the kitchen to justify the $2000 duct charge on the price list. I felt that this salesperson was recommending the package rather than my needs. He did have a checklist of items to go over, so it felt like we had a more complete conversation minus a technical discussion on how to ensure that all the Lennox components fit my needs and achieve the best possible SEER. I think that after reading so many posts here and getting so much advice, I was expecting more. I suppose that I'll find out more when I get the quotes via e-mail and see how detailed they are. Also, I'll see how they respond once i start making changes to the equipment based on opinions from this board.