Introduction

This article is a follow-up of my previous (old)  French post “Domotiser une ancienne chaudière mazout : Gestion du thermostat“. That previous built used a custom firmware to control relays, measure water temps and show status on a OLED screen.

Time has past and Tasmota is a very capable and easy to integrate framework. I don’t use much the OLED screen so I decided it was time to get rid of that old custom software.

Obviously, Tasmota supports OLED displays, I might consider going down the docs at Tasmota > Features > Displays. A custom build using USE_DISPLAY_SSD1306 will be required as well as quite some read.

Hardware

This built is similar to Monitoring a boiler using Tasmota on ESP8266 and DS18B20 sensors but adds relays to control the Power and Circulator.

Another option is to use an OpenTherm interface but that’d require changing my physical thermostat. As far as possible I prefer non invasive hacks that are easy to reverse.

The below overview shows the main components such that:

• WeMos D1 Mini ESP8266 is used as the main controller
• 5V relay module is used to control power and circulator (heating)
• DS18B20 are used to measure outgoing and returning water temperatures
• Optional : I2C OLED 0.96 inch display module from my initial build using Homie. This post does not cover its use with Tasmota.
• Optional : DIN Power Supply (5V, 15W) to power the build
• The Zigbee network controlling the radiators valves, this is out of scope for this post:
  • Sonoff ZBDongle-P as Zigbee gateway
  • Zigbee radiator valves from MOES at each radiator

Overview

Wiring temperature sensors

Wiring relays

Test bed and wall box assembly

Breadboard

Protoboard wiring Front

Protoboard wiring Back

Breadboard and assembly

Test bed on desk

Test bed in wall mount box

Bill Of Materials

The BoM is exactly the same as for the Monitoring a boiler using Tasmota on ESP8266 and DS18B20 sensors except you need one or two relays to control the furnace power / circultor.

Software

Tasmota

Just connect your WeMos D1 Mini ESP8266 to your computer over USB and install the regular Tasmota image using https://tasmota.github.io/install/.

To configure your board, use Module type = Generic(18) with below settings (adjust based on your actual wiring):

• D5 GPIO14 : Relay_i #1 for Power
• D6 GPIO12 : Relay_i #2 for Circulator
• D7 GPIO13 : DS18x20 #1 – As the DS18B20 uses a bus, a single data pin is required for both sensors (or more!)

Finally configure the MQTT to point to you Home Assistant server.

Home Assistant

In HA, make sure to setup the Tasmota integration, this will detect your Tasmota device over MQTT and setup the entities automatically.

Once entities are present in HA, I included them as shown below.

Here is the YAML configuration

type: vertical-stack
cards:
  - cards:
      - show_name: true
        show_icon: true
        entity: switch.tasmota_furnace_relay_power
        hold_action:
          action: none
        tap_action:
          action: toggle
        type: button
        icon: mdi:power
      - show_name: true
        show_icon: true
        entity: switch.tasmota_furnace_relay_circulator
        hold_action:
          action: none
        tap_action:
          action: toggle
        type: button
        icon: mdi:engine
    type: horizontal-stack
  - type: history-graph
    entities:
      - entity: switch.tasmota_furnace_relay_circulator
      - entity: sensor.tasmota_furnace_ds18b20_1_temperature
      - entity: sensor.tasmota_furnace_ds18b20_2_temperature
    hours_to_show: 8
    refresh_interval: 1
    title: Chaudière

Conclusion

I enjoyed working on this build and it is probably the hardware I use the most for my home automation. The use of Tasmota dramatically simplifies its deployment and maintenance.

However this is only one of three big parts for my heating automation:

1. Furnace control : This post
2. Radiators control using Zigbee valves : It’s as simple as adding the Sonoff ZBDongle-P and some Zigbee radiator valves from MOES
3. Full radiators automation : Home Assistant to control per room valves on a schedule

I still have some work to put on automating the heating itself. I’m currently relying on the physical thermostat and manual circulator control.