Just bought a new (<6 years old) house and it's two stories, but only has a single furnace in the attic and a single condenser outside. However, there are two thermostats that work (semi) independently of one another.
The master on the second floor seems to have more options than the first floor thermostat. They are Honeywell models and I know there is a damper control in the attic vents to turn off the air flow on one side or the other if it's thermostat is set to off.
I'm sure I cannot have heat upstairs and cool downstairs since it's still just one system. But I can control the temperature per floor with each thermostat.
So my question is can I replace this master/slave combo with a Sensi programmable on each? I had them at my previous home and love the ability to easily program and control with my phone.
Will they automatically talk to one another with regard to "heat on" for example? Is there something else in the attic/furnace area I should be looking at as well?
Any tips or advice would be helpful as well. 🙂
Best Answer
The most common way that two thermostats work with one HVAC system is through the use of a zone controller like one of these. They can be installed near the air handler, but it could also be in a nearby closet so it can be monitored or adjusted without going in the attic.
The zone controller makes all the decisions about controlling dampers and calling for heat or cool, so the thermostats don't have to know they are not controlling their own independent system. The thermostats are "standard" and don't need any extra features or wire connections, so you should be able to easily replace them with a smart thermostat and follow the normal installation instructions.
You can verify this by finding the zone controller, or just look at the wiring on your current thermostats. If they have the typical R, G, Y, W, C wires and nothing extra then its a safe bet they are standard thermostats. If they have some additional wires (and you don't have a heat pump or multistage heat/cool) then it might take some more research. Also look up the model numbers of the current thermostats.