Two HVACs with two thermostats: any advice?

I am buying a 34 y ear old single-story house that has two HVAC units, and two thermostats. One is in the bedroom corridor; the other is adjacent the living room. This is not a single system with two zones, but two separate systems, two heaters, two outside units for the AC.

My Questions:

  1. Is there some need of any kind to set up any automations to have the two systems where they will not argue with one another?
  2. For schedules I am thinking the stat for the living room goes lower than the bedroom corridor one in the winter, that sort of thing.
  3. I'm thinking two ecoBees of some sort.

I'm open to suggestions and ideas. Thanks!

Don’t use the systems in “Auto” mode. Based on outdoor weather, define ranges when they’ll be in either Heat or Cool mode.

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I have two units as well. I use two wifi connected thermostats. I use alexa to control both of them. Verbal commands are easy. I did do some control with webcore for a while, but our schedules are so random that firm heating/cooling schedules just did not work.

I planned on that already as Alexa does not play nice with Auto.

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It may not be a problem depending on how the duct systems are laid out. You probably have one independent system for the living area and one independent system for the bedrooms. This is really a good arrangement. The key to deciding if they conflict will be the location of the return air grilles. If the living area return air grille is in the living area and the bedroom return air grille is in the bedroom area, they should be fine. If the return air grilles for both systems are in a common corridor, it may affect the temperature control.

You might also verify that each thermostat is located in the area that it is controlling, but it sounds like they are.

If the supply air grilles, the return air grille, and the thermostat for each system are located generally in the area they serve, then you should be ok.

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From the thermostat's point of view, it doesn't know if it is zoned or on separate systems, and it would be the same as any zone system, as far as heat migrating from one zone to the other zone.

I had wifi thermostats for a bit, but I switched them to ZWave to stay local, and I had issue with the response time for wifi thermostats, when responding to settings made in automations. Zwave is nice and instant.

There is a Thermostat Scheduler app built in to Hubitat. I don't use any of the built-in schedule stuff on the thermostats themselves.

I have 3 systems on ecobee. I switch them from heat to cool seasonally. I also set them to cycle the fan at least 10 minutes every hour. They toggled off if the smoke alarms go off. Toggling them on remotely is nice when returning from holiday.

I have them integrated into 3 home systems in the same house. I like it

Excellent idea! I'm adding that to my setup.

If there are two complete systems, I doubt they can talk to each other. However it would be nice if you could make it so the don't start at the exact same time. I don't think this can be done from the thermostat.

I've always wondered about this, but never slowed down enough to really think it through. Would you elaborate on why you approach it this way?

If you leave them on Auto, there is a possibility that a cooling call on one thermostat will trigger a heating call on the other. Or vice-versa.

Consider that challenge in an open floorplan where heat rises. Or when people leave bedrooms open. Often an older house will radiate heat through the roof. The upper floor may switch to cool and that cool air may move down a floor and potentially call for heat.

Easy enough to avoid. In many locals the seasons change enough to switch. In other places temp ranges during the day may be so wide that you want to use auto

Ah so you were talking about the OP’s context with two thermostats. Where there is only one, then auto should be alright. Concur?

Yup

Depends on of you have zones.

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