The problem with explaining how refrigerators and freezers work is that an even barely sufficient explanation requires knowledge of rudimentary thermodynamics. An insufficient explanation might go like this: Electricity drives a motor that pumps a fluid through the refrigeration plumbing. This fluid, which typically is a gas at room temperature and pressure, has the property that when compressed it gets hot, and when expanded, it gets cold. (This is true of all gases per the Ideal Gas Law.) If the cold gas (now a liquid) is put into contact with a warm surface and allowed to expand to its gaseous form, it absorbs a lot of heat from the surface. When this gas is further pumped and compressed, and then subjected to a surface cooler than it is, it gives up its heat and condenses back to a liquid that is warmer than the exterior ambient. However, when later in the loop expended back to a gas, it gets colder than the interior air and can thus cool it. The expansion part occurs in an expander, and the condensation part occurs in a condenser. The condenser in your refrigerator, like the condenser in your car air conditioning, is a radiator that moves heat to the air. The expander in your refrigerator, like the expander in your car air conditioning (usually buried in ducting and less easy to see) is a radiator operating in reverse by absorbing heat from the air passing through it. The efficiency of this heat transfer loop is mainly determined by three processes: the efficiency of the thermodynamic cycle being used by the system, the motor electrical to work efficiency, and losses from friction moving the gas around. The thermodynamic process prohibits attempts to get something from nothing, or even break even (no perpetual motion machines; no free work). In principle, two separate systems, one for the refrigerator and one for the freezer can be sized and optimized for each such that the total power used in some standard environment is not greater than that used from a freezer only single system that controls the rate of cold air moved to a refrigerator. It could with careful tuning be more efficient. Analyzing such systems is fairly complex and specialized, and designing and building prototype optimal ones (for aerospace applications say) can cost millions of dollars. For residential units, some standardization is expected in selection of compressors, condensers, and expanders such that the last erg of energy savings is not going to be met. One expects for residential units that the efficiency will be as noted on the sticker for some environment, and the buyer has to determine whether differences in electricity cost, differences in purchase cost, and differences in other features make the purchase worthwhile. kas

Hi tigerdunes, I'm in Atlanta Upstairs and downstairs equal about 2000 square ft. I don't know about the linesets. Downstairs alredy has dual fuel setup. 80% variable Ultravation The sales guy was really pushing the xl16i. I did ask about the xl15i after reading your posts. I will check on local dealers that carry Am standard, I know they are the same as Trane. I have another Trane dealer working on a quote. I have another guy working on a quote on some Goodman stuff, but not so sure on the quality. I think he's a good installer, and he said that I could get the 10 year parts and labor. I know his quote would be cheaper. I don't want to be cheap, I just want a good install, a good system,something that will save us on utility bills over our old 16 year old system, and something that's going to last. We hope to be in our home for a long time, but I don't want it to take twenty years to break even. Thanks for your help.

I'll try to give my input where I can with your questions. I like the 2-compressor, 2-stage system because it is 50% capacity on low stage, so longer run times which means better comfort. I think your pricing is great on this equipment. Only thing that concerns me is potentially having to change out two compressors (which I probably wouldn't even bother doing) should one go bad and contaminate the system (which is the worst case scenario). Single compressor dual stage systems usually run around 80% capacity, give or take, on low stage, so less advantage with humidity control. So, as your quotes stand now, I like the American Standard option. The 2-stage unit will be nice to have for the main house, since you won't always need 5 tons. While generally I wouldn't recommend a 2-stage unit for just a master bedroom, they are really the same price before extended warranties are factored in. Since many extended warranties per system run $700 each, I think $1000 is reasonable for both to protect you from any failures. I'm not sure how reliable the components are--I haven't read anything terrible about them to date--but you would potentially have the extended warranty to eliminate that fear. And I wouldn't expect much more than 11-14 years out of a system built to today's standards, especially if you live near the coast and/or the system's is built around improperly sized/designed ductwork.

location? What are your rates, electric/kwh and nat gas/therm? Be specific. Who is underwriting the labor warranty? While the ext labor warranty may provide peace of mind, it is my experience it is not worth it on a quality system. Remember though, it is homeowner's responsibility to see that new system is properly registered for warranty. Just read a horror story on a Carrier Infinity system where dealer and homeowner failed to register a system. I can not see your ductwork. Other than age, are there known problems? Hot and cold spots? Leaks? Adequate returns? Have you been given a replacement cost? The Amana Mdl number-APG15 or SPG15? Please check and advise. On the surface, it appears Amana has a better warranty than Trane. This should be scrutinized closely especially understanding exclusions. You are being quoted 3 ton units? What is heating output? Both the Trane and Amana have two stg gas valve that will require a true two stage thermostat to properly operate. The Trane has a var speed blower motor. Not sure if the Amana does. May be just a high eff motor but not var speed. This might be important for better dehumidification. You should check on this. After further study, I think the Trane is a better unit with the var speed blower motor and two stage AC compressor. Amana warranty though looks stronger. Post back. IMO http://www.amana-hac.com/Products/PackagedUnits/15SEERAPG15.aspx http://www.trane.com/residential/en/products/heating-and-cooling/packaged-systems/xl16c-packaged-gas-elec.html This post was edited by tigerdunes on Fri, Nov 7, 14 at 6:41