Say I set my thermostat to 72 F. (Yes, I'm in the crazy U.S. and use their strange measurement system). I am under the impression that an HVAC system will wait for the temperature to be off by a certain threshold before turning on and then it might even overheat/overcool by a degree or so to prevent short cycling. For example, if it's summer, my AC might kick on at 73/74 and cool to 71.
First question - is that accurate?
Next, I am wanting to know about dual zone. I see two possibilities here:
Two thermostats trigger a cooling cycle or heating cycle when needed. The furnace/AC is turned on to handle the requested zone(s) at the time. This seems very inefficient as Zone 1 might get to temp and shut down while Zone 2 could trigger a cycle again 5 minutes later.
Two thermostats communicate between the furnace/AC and themselves. In my first example, let's say that Zone 1 hits 74 and turns on. Meanwhile Zone 2 is at 72. A 'smart' system might open the dampers in Zone 2 to cool it down to 71 while it's also working to get Zone 1 down to 71. Even though the thermostat at Zone 2 would not have triggered this itself. These dampers would only open for a short time but would prevent Zone 2 from requesting a cooling cycle shortly after Zone 1's cycle turns off.
Which of these is it? Or is it something else?
Last question - does it require special thermostats?