You folks are great. I'm taking your advice to heart. I will relax a few days and see how the new CPH setting works.
I think that I have the installation manual and have briefly looked over the 20 pages. This looks like the one for my stat.
Title from the manual: TH8320U and TH8321U Touch Screen Programmable Thermostats
The TH8320U and TH8321U Touch Screen Universal Programmable Thermostats provide electronic control of 24 Vac
heating and cooling systems or 750 mV heating system. See Table 1 for a general description.
Table 4. Main Installer Setup Menu.
The options run from 0170 to 0710 once you get beyond the 0120 to 0160 for basic date/scheduling, etc. I must say most of it is way over my head. But it makes good reading.
I wouldn't feel comfortable making any changes since it's important to me to be able to tell my HVAC folks that I haven't made any changes. They must be able to trust me not to tamper with the settings like I trust them to make the proper changes. Changes are for them to make. I just want to learn so I can have an good idea how the process works. I may scroll through the settings and document my setup and learn more about those settings. I think that would be appropriate.
So the economic balance point is just an arbitrary temp that one sets to lock out the heat pump and force the aux heat on? For example, one can set a 20 degree (or any number) balance point in the stat somewhere. On my system there is no outside stat or sensor.
Very interesting. Going over my notes with my contact at the Heating and Air company, I find that I was told not to worry about the outside temp. The heat pump will turn to aux when it finds it can't keep up. Maybe it's setup to turn on aux if it falls behind x number of degrees? I've never worried about it, the heat pump runs almost all of the time. It's rare to see aux on and that's probably more due to defrost cycles than to outside temp.
It is possible that the outdoor unit has a "built in" sensor. There are some units that have a board and/or snap disc type sensor instead of the wired sensor connected to the thermostat.
Usually 3 degrees difference in the set point and room temp brings on the back up/aux heat.