How do Nest thermostats work with different heating/cooling zones?

[mboons]

We have two heating zones on one floor but only one cooling zone; both thermostats are currently non-Nest thermostats.  One thermostat is switched between heating and cooling as necessary, and the other thermostat is switched between heating and "off".  (The same setup exists on the second floor.)  Can a Nest thermostat be set up the same way, so that it calls for heat when it's too cool but does nothing when it's too warm (because the other thermostat will call for cooling)?  Thanks for any hep you can give me.

- mb

[CoolingWizard]

@mboons ,

When you have “zones” you have to have a controlling thermostat in the zone.  The HVAC equipment is wired to the zone controller, and the thermostat is too.  Most zone controllers have support for multiple zones.  So you will need a nest thermostat for each current zone controlling thermostat.

AC Cooling Wizard

[mboons]

My question, though, was whether a Nest thermostat can be set up with only a connection to a heating zone and not a cooling zone, or if it requires both a heating and cooling connection.

[CoolingWizard]

Basically, a thermostat is nothing more than a local switch, and what I mean by that is the thermostat takes power coming in on the R terminal, and depending on what system mode is set, either heating, or cooling. If the set-point temperature is exceeded then the thermostat will call for the service. That is if it is in heating mode, and the temperature falls below the set point, the thermostat internally connects the R wire to the W wire. If the system mode is cooling, and the temperature rises above the set-point, the thermostat connect  R wire to the Y wire to call for cooling.
Now then, on an old non-intelligent conventional thermostat, if there’s no Y wire, and you set the mode switch to Cool, and the thermostat connects R to Y,  nothing will happen.  With an intelligent thermostat, like the Nest Leaning Thermostat,  It knows what wires are attached to what terminals. Not by the color, just by the fact that there’s a wire attached. In doing so, It knows if there is Cooling available. It will know that if there is a wire attached to Y. With the Nest intelligent backplate, the display can actually sense the presence of the wire. 

If there’s no wire attached to the Y terminal in the nest, it knows there’s no cooling capability in the system. 

In short, the Nest thermostat only knows which terminals are in use. So if there is only R, W and G, the nest will know there is only heat , fan and no cooling. So it will work just fine.  It will not allow you to select Cool.

AC Cooling Wizard

[zoeuvre]

Hi folks,

@mboons, thanks for reaching out to us. I want to check if you managed to see the response above. Please let us know if you still have questions or concerns, as we'll be willing to assist you more. 
 

I appreciate your help, @CoolingWizard. 

Best,

Zoe

[zoeuvre]

Hi there,

I want to check and see if you are still in need of any help. Please let me know, as I would be happy to assist and answer any questions you may have.

Thanks,

Zoe