"Posted by ryanhughes (My Page) on Tue, Apr 30, 13 at 14:27
There are a few varieties of VisionPRO 8000 thermostats. The TH8110 is just a 1H/1C thermostat that is not meant to control multistage heating/cooling. The TH8320/TH8321, however, will proper control the 2 stages of heat from the furnace based on demand, similar to the algorithm used in the IAQ. What the 8320/8321 will not due compared to the IAQ is stage the back-up heat (the IAQ in that sense is a 4H/2C thermostat) -- that would be on a timer. Not relevant here as you have a condenser (not heat pump) and 2-stage furnace. The IAQ also has the nice feature of dehumidification on demand, as mentioned, to signal the variable speed blower to reduce speed for further dehumidification. All of these attributes, however, are heavily dependent on how the installer configures the thermostat and control wiring. Another reason why a proper installation is critical."

Ryan, thank you for your post from yesterday. I would like to followup with some questions.

In my neck of the woods, there is an old saying that goes like this.
"There is more than one way to skin a cat."

My question is if it is the best way and cost effective?

Will the 8320/8321 be less effective than the IAQ in keeping a two stage furnace on low stage based on demand? You and I know that there are way too many new installs on two stage furnaces with less expensive and sometimes wrong thermostat that just use the timer at furnace to control staging and effectively turn a nice two stage furnace into a single stage furnace that operates on high stage practically all the time.

If I understand correctly, you are saying the 8320/8321 are not recommended for DF systems even with an outdoor sensor whether HP condenser is single stage or not?

I realize that there are other features that the IAQ has over the 8320/8321 such as dehumidify on demand and handling auxiliary equipment such as a humidifier.

I don't like to see a dealer cripple a nice system's capability because of a less expensive and wrong thermostat. A pet peeve and often one sees nice Infinity systems without the Infinity controller. I am sure you agree.

One of the nice features of this forum is to share experience and learn.

Thank you again.

TD