"Given that all these systems are 15 SEER with variable speed air handlers and txv's does it matter much if they are over sized?" -- Yes. Oversizing decreases efficiency (off/on cycles often cost more money as well). What is the area (in sq. ft.) of the upstairs? They may have oversized it slightly since it is upstairs and heat will rise. "When the air handler slows down, what exactly happens? Does the liquid freon remain under pressure after the compressor stops [I'm assuming that the compressor is constant speed on/off] and then slowly release into the evaporator coil as needed?" By slow down, do you mean during an off cycle? After the compressor turns off, the coil will still remain coil for some time. During dehumidification mode, the air passes air slower over the coil, thus increasing latent (humidity removal) capacity. "Given that all these systems are 15 SEER with variable speed air handlers and txv's does it matter much if they are over sized?" Oversizing is oversizing; however, the variable-speed blower can increase humidity removal by slowing the blower down during a call for dehumidification. "In other words, will I still get the dehumidification that I need, and also keep my power bills low if the units are oversized by 1/2 to maybe even a full ton?" Oversizing SIGNIFICANTLY can run up power bills and hurt the ability to remove humidity. Being 1/2 ton oversized may require you to set your thermostat a bit lower, but I don't think you'll see any major issues. Remember, nominal capacities aren't always actual capacities. If your duct leaks, you lose capacity. Sometimes coil matchups change capacity from what the unit is rated at. (i.e. 22,000 btu's instead of 24,000 btu's). It's really all guesswork from here without seeing a copy of the load calculation, if one was performed.

I've been keeping track, but had not done any analysis until you posed the question. As you can see from my comments, I chose NOT to go with the variable speed AC/Heat unit. Even so, I've seen a notable reduction in my utility bills. And keep in mind that this is only replacing the upstairs AC / Heat. The downstairs in on the verge of failure after 16 years, so I will be doing something similar with it in the near future. Here's my analysis of pre/post installation: Pre-New System Post New System Comp Periods 9/1/2014-5/31/2015 9/1/2015-5/31/2016 Difference % Change Avg Temp (Fahr) 55.1 57.7 (2.6) Average Bill $'s$252.18 $208.06 $44.12-17% Avg Cost/Day $'s $8.33$6.83$1.50 -18% I'm down about 18% on a per day basis. By my reckoning, about 4-5% of that is due to lower natural gas rates, and another 4-5% is due to the difference in temperature over the winter. So net-net, down about 8-10% on tried and true technology. I would expect to get something similar when I replace the downstairs unit.

You appear to be a DIY type of guy Doug so I'll toss out a couple of suggestions which won't cost you much at all if building your own system is what you want to do. If you really want a a full range variable speed motor for a blower I'd suggest searching Craigslist for a free high end tread mill. You'll get a DC brush motor, Dc power supply and controller to adjust the speed full range. But for a blower I'd personally go with the next option. Find a ECM (X13) blower motor from a giveaway furnace and build a mounting frame and add a pulley. The majority of these motors have 5 taps available with any one tap being energized with 24 volts Ac at any one time to select the speed. With a multi position selector switch, 6 low voltage wires (24v ac) you can select a speed preprogrammed into the driver microprocessor specified by the manufacturer of the furnace. The difference; the treadmill motor (similar to the Granger motor you picked) is a single phase permanent magnet DC motor with a separate motor controller but they're not old school controlled with a rheostat, but will usually consist of a PWM to vary the speed. The ECM motor is a 3 phase permanent magnet DC motor with a built in motor controller and processor, but the communication between the furnace and motor is model specific so knowing what you have will determine how you control the speed. Just make sure it's not digital serial interface communication, but most will be Low voltage AC or maybe DC and if you're lucky you can find one with PWM communication. A PWM board would only cost around $10 to vary the speed full range. What Mike said about over heating a AC motor without a Variable frequency drive is correct and the Vari-speed you picked isn't one. What Jim is saying..........I .never heard such a thing but he did mention California so who knows, I opened a package with metal brackets a while back and the brackets had California warning sticks stating they could cause cancer, go figure.

Amana AVXC200361, CAPF3743C6, AMVC80805CX I believe the middle one is the heat pump and blower unit? Showing my ignorance here ;) -- just pulled these codes from the project quote. Nope, none of these are a heat pump. The middle one is a 3 ton - 3 1/2 ton upflow coil. The last one is 80% gas furnace 4 ton. I shared these thoughts with the person who sold and installed the system and was told over email, "the system runs as promised, there is no way you would know the fan speed unless you were into the diagnostic side of the controls". Am I wrong in thinking that the fan speed change should be noticeable just by its force and noise level? Varible speed blowers when ramped can generate air noise, especially if there are issues with the duct system. Was the duct system replaced with this install or just equipment? The more air you push pull thru a system? Variable speed are quieter, but only if your duct system is capable of handling the air these can generate. The algorithm to the blower can be adjusted. But the better approach is to design a proper duct system to handle the air flow. Because you came from a swamp cooler before, heating loads tend to be lighter and so the duct system for those is likely inadequate for AC. If the duct work was replaced with this job, he should at least try to change the algorithm to the blower. The logs always show the state 'compressorCoolStage1On' when on -- so there is no info there on what speed the fan is running at and I do not know if the thermostat is controlling the fan or if that is happening elsewhere in the system if at all. These systems are communicating, but Amana as well as Daikin and Goodman brands moved the communication part to the furnace. They claim you can use any thermostat with them. The signal from the thermostat merely gets the cycle started. From there the communication aspects of this system take over. However, smart thermostats like the ecobee (nest are often worst offenders) can disrupt the lengthy run times of varible speed / inverter type systems. Disrupt means the signal from the thermostat tells the system to shut off. When that happens / the new start up the process begins again it could take up to 20 minutes of run time for the inverter to find it's bearings. Because the way these run is to mostly keep on running. That is the most efficient form for these. These machines are mostly looking for nirvana or the load of the structure to minimize off cycles. So when you see long run times along with adequate comfort --- that is what you want. That is how they are designed to operate. There are other things that could cause stop / restart outside that of the thermostat. A test would be to buy a cheap run of the mill thermostat / remove the ecobee and use the cheap thermostat for awhile if you believe your ecobee might be part of the problem. I have a customer that uses an ecobee with Bosch inverter with no issues for over 2 years now. But Bosch advises against using smart thermostat because the thermostat will sometimes try to think it knows best how to run the system. I don't know if that is an issue or not, merely a guess of something to pay attention to. -------------- Does the unit cool properly? Are you comfortable except for the blower noise? I service the Katy, Texas area.