ENtire unit just went out. HElp!!!
I only use 2 brands in my installs, For those who want a less expensive unit, but one that uses readily available parts, i recommend Goodman, formerly known as Coleman, they use standard AO smith motors that are available everywhere, and on A/C units, the motors are the most common things to go out. For a deluxe unit that will go for years without being serviced, i install Lennox. Lennox uses Emerson motors, that are better quality than AO smith, but more expensive, they also use scroll compressors, which are much tougher than the less expensive hermetic type compressors, the bad thing about Lennox is that their controller boards are very expensive and sometimes hard to find. The best thing to do is to call several companies in your area and find out what the most common brand is for your area, so when something goes wrong, the parts can be sourced quickly.
I am very particular to Carrier and Comfort Maker. I have installed them since the mid 90's with no call-backs or problems. They are great units. As for the size of the unit you need.... it depends on your home. If it is an older home, with standard windows, standard insulation, etc, with average 8 ft ceilings, you would need about a 3 1/2 ton unit. If it is a newer home, with double pane windows, good insulation, 8 ft ceilings, etc, you would need a 2 1/2 to 3 ton unit. If you have vaulted ceilings, those have to be taken in to account because they cause additional heating and cooling loads and increase the size of unit you need. Make sure not to get an entry level builder's model which only has a 5 year warranty on the compressor. Spend a wee bit more and get the better model with a 10 year warranty.
In my opinion you should be searching for the best installer rather than best equipment. Most of the major brand equipment today is just as reliable as the other. They all have third party parts that you will usually find in one unit to the next. Just make sure you get a unit with a scroll compressor, 410a refrigerant, 10 years warranty on all parts (20 years on heat exchanger), and a GOOD installer/designer. If a system is set up and installed properly then you shouldn't have many problems with your system. If you want an answer for the best heating/ac brand all I can say is that the Rheem heating and cooling products have been ranked number one in fewest repairs in consumer reports.
