OpenTherm weather dependent heating control

[akamming]

My current boiler is end of life and i needed a new one. My current thermostate is already Weather Dependent, but cannot take advantage of the modulation features of a new boiler and i didn't like the limitations of all the commercial propositions of a smart weather dependent thermostate. So i decided to create one myself with full domoticz integration, so i could have the following advantages:

• Lower cost for the same functionality as my old thermostat: 30 EUR of material against 300 EUR for a commercial system (and then i'm ignoring the fact that after initial price, some also need subscriptions)

• fully opentherm compatible, with all advantages of a modern modulating system (many commercial weather dependent systems only support on/off protocol)

• no private data (e.g. wheter or not i am at home) in a public cloud

• Full control of the boiler if set to manual

• All boiler sensors available in domoticz and the ability to send notification (e.g. on low water pressure)

• Domoticz timers have much more options than the ones on commerical thermostats

• No need for an expensive (also 100+ EUR) outside temperature connected to the boiler (any temperature device in domoticz can be used, e.g. buienradar)

• Full domoticz integration, so heating be part of scenes, scripts and other events

I used the hardware of which installation and build instructions can be found here: http://ihormelnyk.com/opentherm_thermostat, but wanted different software for 2 reasons
1. Instead of a "normal" thermostat, i wanted a weather dependent system ("weersafhankelijk regeling" for the dutch among us)
2. I wanted full domoticz integration

and the good news is: I succeeded by creating a combination of changed firmware and a domoticz plugin. And since i like sharing, i put it on github: https://github.com/akamming/Domoticz_Thermostate_Plugin. Feel free to reuse what i built. To help, i created installation instructions, which can be found in the Readme.md file on github.

it is now working OK for a few days, but might still be buggy. if you encounter anything, just let me know ...

[akamming]

I've added a major feature: The plugin now also can act as a regular OpenTherm modulating thermostat!

A button ("Fireplace/Weather dependent mode") makes plugin switch between weather dependant mode or modulating thermostat mode

In the Netherlands the temperature is currently too high (my house already reaches 22 Celcius without heating switched on) to do testing on the mechanism, so i am looking for someone who can test this feature..

[renerene]

Can you give an update? Is the thermostat working?

Stumbled upon this post while looking for a replacement of my domoticz on/off control system. My old heater will be replaced by a modulating Intergas Kombi Kompakt HRE36/30. Currently I'm using a zwave relais and Smart_Virtual_Thermostat for thermostat function.

This could be a nice, simple wireless thermostat. The weekly program, temperature sensors and dashticz interface all can remain the same as my current setup.

[mikew]

Hi renerene and akamming,

In search for an OpenTherm gateway which I could connect to Home Assistant I came across this and the other post (viewtopic.php?t=36137) of yours.

Does any of you know a solution to connect OpenTherm and Home Assistant either as a pure gateway or master for full automation?
I also found https://www.nodo-shop.nl/en/48-opentherm- but that only offers LAN or Wifi connection. Ideally I'd like to use the zigbee mesh network. Doubt there is a suitable and cost effective z-wave solution but please prove me wrong about my assumption.

Many thanks in advance
Mike

[stevedh]

I'd look at investigating a raspberry pi z-wave shield and try using that with an opentherm shield, .. may or may not give you what you want.

[seal]

@akamming: i tried to compile your handler from git but i'm getting erros:

Code: Select all

Compilation error: 'class OpenTherm' has no member named 'getOutsideTemperature';

Im using all libraries as was in your readme

[jusik]

Wrong library opentherm,
'class OpenTherm' has no member named 'getOutsideTemperature'

[kniazio]

I have been using your plugin for a few days and I am delighted with it.
Everything works as it should. There's only one detail that worries me. When the boiler burner (modulation) goes down to 0, -125 values begin to appear. Everything still works. Where can these values come from?

[akamming]

@akamming: i tried to compile your handler from git but i'm getting erros:

Code: Select all

Compilation error: 'class OpenTherm' has no member named 'getOutsideTemperature';

Im using all libraries as was in your readme

sorry for late reaction. this is fixed in a later version. Should work now...

[akamming]

I have been using your plugin for a few days and I am delighted with it.
Everything works as it should. There's only one detail that worries me. When the boiler burner (modulation) goes down to 0, -125 values begin to appear. Everything still works. Where can these values come from?

i wouldn't be worried. The firmware just reports the raw data it gets from the sensors. The OT protocol (as i understand, but only have one boiler to test, also a hobbyist...) is nog 100% standarized.

The thermostat part in which you can tell the boiler to which temperature to heat or cool the system is mandatory, so every thermostat would really act as a thermostat. But on a lot of other commands brand specific implementations are allowed.

e.g. my previous boiler did report pressure. My new one just reports zero on that sensor.

The same way this -125 on modulation can have some meaning for your brand, which would probably be recognized if you have a thermostat from the same brand. My firmware/plugin just reports the raw data from the sensors.

[kolb]

I also used the opentherm adapter and library found here: http://ihormelnyk.com/opentherm_thermostat.
I connected both boiler and iSense room thermostat to the adapter and hoped to be able to control my boiler by iSense thermostat as well as by domoticz. However, with both connected, the iSense gives a F203 communication error and the OT commands result in response time-outs. When I disconnect the iSense the OT commands seem to function properly.
My question is how can I connect and operate the OT-adapter and still keep the iSense thermostat functioning (for the rest of the family).

[akamming]

For whoever is using this plugin to control their heating/cooling with the opentherm adapter from Ihor Melnyk:

I moved the functionality of the plugin to the custom firmware (https://github.com/akamming/esp_domotic ... rm_handler).

So if you update you firmware of the ESP8266, you will no longer need this plugin. I therefor stop maintaining this plugin, since this is a much better solution (and is more generic. The thermostat is now automatically available on any home automation system which supports the mqtt autodiscovery protocol)

[Maciek90]

Is there any way to update my esp8266 via OTA, or do i have to update via arduinoide by connecting usb cable?

[akamming]

If you are regering to the firmware I described above: that one support ota upgrades.

But since you also need to upload the data files with littlefs, then ota upgrade is Only supported of you use the Legacy version of the arduino ide (can be found on the software page on the arduino site)

[Maciek90]

One more question. Can I install this firmware on WT32-ETH01? I would prefer to have a LAN connection to my boiler instead of wifi

[akamming]

Probably Will work, but only after some code changes

The code Will now look for a wifi config first so that has to be changed for this device

I also only tested On esp8266 platform. I never compiled on esp32. So this might also trigger Some code changes

If you have Some coding skills, you can make the changes and create a pull request

[Maciek90]

Unfortunately my coding skills are very poor. Maybe you are planning to create such a modification?

[akamming]

Unfortunately my coding skills are very poor. Maybe you are planning to create such a modification?

Sorry… no plans and no reason to do so… works 100% stable using wifi…