HVAC control instead of a smart thermostat


As of now I have a “dumb” thermostat controlling my HVAC system.
I want to be able to control the HVAC system via HA without connecting it to a smart thermostat. Are there modules that can provide me with these functionalities without going through a smart thermostat? I don’t want to hang anything on the wall at the end of the day :slight_smile:

Thanks in advance

I’ll ask it differently - is a smart thermostat is the only way to automate my HVAC system?

You don’t specify brand, or supply pictures of the hvac motherboard etc.

SO cant say anything about this.

But most likely you can yes, but also depends on what you have / need

Yes, you’re absolutely right. When I originally asked the question I should’ve been more specific.
The system is a Bryant 310AAV/JAV. I also found the information booklet the original owner of the house kept. Here’s the j box page from that booklet - hope this helps

Based on my (admittedly limited) understanding of HVAC systems, the thermostat is basically acting as a controller to open/close circuits for the heater and blower motors. If you wanted to over-engineer a solution then a pi or other device could read the current temperature (whether through an attached sensor or through an external sensor via Home Assistant) then active a switch to connect the +24V to the relevant wires to active heating/cooling/etc.

This is what thermostats are already doing with their internal temperature sensors. Building your own solution to this may or may not be more work and cost than finding a locally-controlled smart thermostat, where engineers have already done the hard part of designing the system and putting it into an attractive case.


I have less understanding of HVAC systems than you for sure!
If it was implied from my original post that this is what I want to achieve then I’m misunderstood here.

All I want is to a have a thermostat that I can control via HA and that isn’t mounted on the wall where the original thermostat is now mounted.

The area in the house where the current thermostat is mounted is where I plan to have a smart screen, allowing access to all my automations. So it feels really redundant to have a smart thermostat there where the same controls would be available a few inches away in the smart screen.

I’m starting to think about simply moving the location back to the garage, as in wire a smart thermostat (that is designed to be mounted on a wall) directly to the wires coming from the unit and run through the walls, only leave them there in the garage


Ahh, I got you! I think you should be able to hook up the smart thermostat wherever, just disconnect the wires from the non-smart thermostat and instead run wires from your new location down to the heater/AC unit.

Is is absolute possible to create a HVAC system using home assistant and your ‘dumb’ thermostat. As I understand the system is controlled by switching on and off. All you have to do is to control this by a ‘dry-contact’ switch. Depending on the protocols you prefer, these are available for Zwave, Zigbee and Wifi

Also you need a temperature sensor in the room you want to control. Connect the dry contacts from the switch to the contacts that where controlled from the ‘dumb’ thermostat. this can be near the heater instead of on the place the old thermostat has been situated.

In HA, you define a generic thermostat like this:

  - platform: generic_thermostat
    name: thermostat
    heater: switch.dry_contact
    target_sensor: sensor.temperature
    min_temp: 10
    max_temp: 25
    cold_tolerance: 0.1
    hot_tolerance: 0.5

That can be used on your dashboard. That’s basically all…

This may help you, might not. How I did it:

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