HVAC Mode

Learn about the HVAC mode setting that you can configure for thermostats.

HVAC mode (hvac_mode_setting) governs the operation of your heating, ventilation, and air conditioning (HVAC) system to achieve and maintain your preferred temperature. These HVAC mode options include the following:

• Heat (heat): In this mode, the thermostat activates only the heating system when the room temperature drops below the heating set point temperature.

• Cool (cool): In this mode, the thermostat activates only the cooling system when the room temperature rises above the cooling set point temperature.

• Heat-Cool or Auto (heat_cool): In this dual mode, the thermostat automatically switches between heating and cooling to maintain a temperature between the heating and cooling set point temperatures for maximum comfort.

• Off (off): In this mode, the thermostat is off, which turns off both the heating and cooling systems for the space.

• Eco (eco): This setting represents Google Nest's eco mode.

---

HVAC Mode Constraints

Some models of thermostats have specific requirements and constraints related to setting the HVAC mode. You can retrieve these requirements by issuing a Get Device or List Devices request.

The following example shows a set of thermostat HVAC mode requirements:

{
  "thermostat": {
    "device_id": "518f692b-f865-4590-8c3e-3849e9984c75",
    "device_type": "ecobee_thermostat",
    "capabilities_supported": [
      "thermostat"
    ],
    "properties": {
      "available_hvac_mode_settings": [
        "off",
        "cool",
        "heat",
        "heat_cool"
      ],
    },
    ...
  },
  ...
}

---

Available HVAC Mode Settings

The available_hvac_mode_settings property includes an array of available HVAC modes. For example, if the array contains ["heat", "off"], it means that you can only set the thermostat to either heat mode or off mode. The availability of heating or cooling options depends on the connected systems. If the thermostat is not connected to a specific system, the corresponding options may be absent.

The following example shows a thermostat that supports both heating and cooling:

"available_hvac_mode_settings": [
  "off",
  "cool",
  "heat",
  "heat_cool"
 ]

---