Air condtioners can't work too hard. They are either running or not. For best efficiency, they should run almost continiously in hot weather. Whatever you do, don't do it so that one or both continually switch on and off. That is known as short cycling, and it will cost you more money in energy and shortened system life than anything else. Short cycling indicates too much system for your needs, and it usually results in poor humdity removal. If you can, set things so that one unit is on almost all the time and the other one never runs.

How bad/good is the carpet overall (except for nail polish)? You can replace the specific area by cutting the area out and replacing with a hidden piece from a closet to match t. Use a good carpet tape and then spray area with water, brush together. I did this when a red candle was dumped over. No one ever knew and it lasted forever. I've also scraped the carpet down to bare back and glued pieces too. Hopefully I do not sound cheap, it has to look good when done. But sure saved a bunch of time and money.

However, if the AC is running to cool the upstairs down to 75, the downstairs will be between 65-68 degrees. There are two systems in this house, but they each do both the upstairs and downstairs on opposite sides of the house. Only the system for the main living area has AC. It is a 16 SEER Carrier. We are looking to replace all the heating and AC units and want to achieve these goals Equalize the temp between upstairs and downstairs Quiet the noise, both of the AC and also the heating/fan Improve efficiency How would this best be accomplished? It's better when you separate floors and use 1 HVAC system to cool upstairs and the other HVAC system to cool the lower floor. Because heat rises and cooling falls that lower level unseparated from the cooling system will always be too cool. You have two systems so it would be best to separate those to heat and cool one level / not a mixture of two levels. It sounds like this might be challenging due to cathedral ceilings and your disdain for spending money with the notation that these ductwork changes can't be done for <$30K. So you're at the point of letting the structure defeat you? Certainly I can understand why, it's not uncommon to find a line in the sand --- a line you won't cross no matter what. If that's the case, sell the "box" and buy a different one. Some homes are a challenge for more reasons than one. Cathedral ceilings, large walls of glass look oh so pretty... you get a mountain view (probably for your Colorado home) but once the heat comes that view gets distorted. Builders do all sorts of things to sell homes, you don't realize the downsides to what they do until you try to live there. ----------------- By separating these areas and zoning the upper floor to the upper floor and zoning the lower floor to the lower floor... how does that work? If you're not calling on the lower level there is no cooling. If the upper level is calling only that area is getting the cooling. Cool air will fall to the lower level but this amount will be much less than supply duct work blowing air down there. I service the Katy, Texas area.

Could this be Google Nests going wonky? I've heard they can do weird things. It's almost like the air is reversed? Hi Davis, It would have to be investigated in person, to see what is happening as Honeywell zoning products aren't that great in my opinion. I ripped out a honeywell zone system with two nests a few months ago. Left the nests because the customer was adamant about keeping them. The honeywell zone system was the problem on that one. Typically the Nest can be the problem eventually as when the Nest ages the battery inside it doesn't retain the charge and it continually steals power from the HVAC system. That can cause erratic behavior when power availability drops, because the nest likes to hog it. A side note I recently replaced a Nest for a customer of mine without a zone system because I was there doing a service call and the discussion of potential other issues came up. They said the nest would shut off the system and restart it a few minutes later which on it's own is not that big of a deal in mild weather -- triple digit heat? Not a good thing. Other oddities, they would try to set a set point and the nest would occasionally say some weird response like that it's not possible right now. I don't know if Google and the power companies might be working together here in Texas as Ercot here has been telling people not to blast AC's / turn them up to 78F to conserve energy. That would be considered a conspiracy theory. So who knows? I've replaced nests over the years for other odd equipment problems. If you like paying me (or others) for service visits then the nest is the hands down winner. I only like them for that reason, they put money in my pocket. I service the Katy, Texas area.