prefixkit Ask an engineerAsk Support RU

Zigbee devices Thermostats and radiator valves

Schneider Electric MEG5779

Merten Connected Room Temperature Controller. Works with Zigbee2MQTT with no vendor hub or cloud: it pairs with a Zigbee stick and shows up in Home Assistant.

Vendor
Schneider Electric
Model
MEG5779
Type
Thermostats and radiator valves
Power
mains: usually a router that extends the mesh
Firmware updates (OTA)
yes, through Zigbee2MQTT

Find it in shops: AliExpress

Links open a search in the shop; some are affiliate links: buying through them costs you nothing extra and supports this site. We do not sell devices or get them from manufacturers.

What it exposes

FeaturePropertyValuesControl
Climatelocal_temperature, occupied_heating_setpoint, unoccupied_heating_setpoint, occupied_cooling_setpoint, unoccupied_cooling_setpoint, system_moderoom temperature, heating setpoint, unoccupied_heating_setpoint, occupied_cooling_setpoint, unoccupied_cooling_setpoint, mode, running state, pi_heating_demandsettable
Max heat setpoint limitmax_heat_setpoint_limit°C · 4…30settable
Min heat setpoint limitmin_heat_setpoint_limit°C · 4…30settable
Max cool setpoint limitmax_cool_setpoint_limit°C · 4…30settable
Min cool setpoint limitmin_cool_setpoint_limit°C · 4…30settable
Display brightness activedisplay_brightness_active% · 0…100settable
Display brightness inactivedisplay_brightness_inactive% · 0…100settable
Display active timeoutdisplay_active_timeoutseconds · 5…600settable
Temperature display modetemperature_display_modecelsius, fahrenheitsettable
KeypadLockoutkeypadLockoutunlock, lock1settable
Thermostat applicationthermostat_applicationOccupied Space, Floor, Not knownsettable
Heating fuelheating_fuelelectricity, gas, oil, solid_fuel, solar, community_heating, heat_pump, not_specifiedsettable
Heat transfer mediumheat_transfer_mediumnothing, hydronic, airsettable
Heating emitterheating_emitterNone, Radiator, Fan Assisted Radiator, Radiant Panel, Floor, Not specifiedsettable
Window openwindow_open—read only

MQTT: state and commands

Zigbee2MQTT publishes the device state to zigbee2mqtt/my_device (my_device is the name you give the device). An example message:

{
  "local_temperature": 20.5,
  "occupied_heating_setpoint": 21,
  "system_mode": "heat",
  "max_heat_setpoint_limit": 17,
  "min_heat_setpoint_limit": 17,
  "max_cool_setpoint_limit": 17,
  "min_cool_setpoint_limit": 17,
  "display_brightness_active": 50,
  "display_brightness_inactive": 50,
  "display_active_timeout": 303,
  "temperature_display_mode": "celsius",
  "keypadLockout": "unlock",
  "thermostat_application": "Occupied Space",
  "heating_fuel": "electricity",
  "linkquality": 120
}

Send commands to zigbee2mqtt/my_device/set:

mosquitto_pub -t zigbee2mqtt/my_device/set -m '{"occupied_heating_setpoint":21.5}'
mosquitto_pub -t zigbee2mqtt/my_device/set -m '{"system_mode":"heat"}'
mosquitto_pub -t zigbee2mqtt/my_device/set -m '{"temperature_display_mode":"fahrenheit"}'
mosquitto_pub -t zigbee2mqtt/my_device/set -m '{"keypadLockout":"lock1"}'
mosquitto_pub -t zigbee2mqtt/my_device/set -m '{"thermostat_application":"Floor"}'

Watch the topics live from the browser: MQTT client.

Home Assistant automation example

Zigbee2MQTT creates Home Assistant entities from the device name. If it is called my_device, an automation in automations.yaml can look like this:

- alias: "Cooler at night"
  mode: single
  triggers:
    - trigger: time
      at: "23:00:00"
  actions:
    - action: climate.set_temperature
      target:
        entity_id: climate.my_device
      data:
        temperature: 18

Check the YAML: YAML checker.

How to pair it

  1. In Zigbee2MQTT click Permit join.
  2. Put the device in pairing mode: usually a long press of the reset button (5–10 s) until the LED blinks; bulbs: switch the power off and on 5–6 times.
  3. Keep the device close to the coordinator or a router while pairing.
  4. Give it a clear name: MQTT topics and Home Assistant entities are built from it.

Exact procedure and model notes: the device page in the Zigbee2MQTT docs. No coordinator yet: coordinator picker.

Similar devices

Idea?