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:
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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.
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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?
Best Answer
Conventional multi-zone arrangements work independently. They don't know or care about each other. They're tuned individually to achieve the desired outcome. Sure, there's some minor inefficiency, but not usually enough to warrant extra equipment costs and complex control algorithms.
Also, such systems would be difficult for homeowners to manage and adjust on a seasonal basis. Heck, many don't even know to change their filters or how to manage humidity properly. How are they going to work sophisticated thermostatic equipment?