OpenTherm Gateway binding

Hi Arjen,

Thanks for the quick reply!
I’m not in a rush and I certainly would like to support you with testing it.
Please let me know when you are ready for it.
For now good luck with renovating your house.

Do you or someone else know if there are examples available of how to set up a MQTT connection with OTMonitor?
I understand the principle of MQTT but did not work with it before.


I am using ser2net to connect to an OTGW with a serial (usb) connection.
Works perfectly for a year or so.


Thanks a lot!
This also works for me.

Hi Arjen,

I’m still a happy and daily user of your binding !
This morning it was cold at home, the boiler was in error-state.
After a few resets on the boiler itself it restarts again.

Do you think it’s possible to add an extra item to the binding that reads the error-flag like in the windows ‘Opentherm monitor’ software ?


This flag could be used in OpenHAB to trigger an alert to the user …

Kind regards,

Hi Peter, nice to hear you are still using this binding! I still use it too, most of the time without thinking about it since it never causes any issues.

Thanks for the suggestion. It would be relatively easy to add the fault indication flag. And with a little more effort it would also be possible to get details from the boiler as to what kind of fault has occured (as long as the boiler supports it).

However, since I am still busy renovating my house… these things always take way more time than expected :smiley: … I won’t be able to work on implementing this feature until the Christmas holidays.


Hi Arjen,

Thanks for your positive reaction !
No problem, I have time :wink:

There is something wrong with my boiler, I received today again the same error (133 = no flame) …

Success with the renovation of your house !
Kind regards, Peter.

Got the esp working with ESP-link. Showing the everything from the thermostat and boiler. However, the binding 0.8.0 does not allow me to configure anything in PaperUI. It just shows the binding, but no channels, no configuration etc. Do I miss something?


Is the source code still available anywhere?

@PGustias thanks for the detailed screenshot, this really helps me in mapping the data sent through opentherm to the binding.

@JdeJong you should be able to configure the IP address to connect to the OTGW device. After that, a complete list of channels should be available in openHAB which also shows up in PaperUI. The sources are currently not available on Github, because the structure of the openHAB sources has changed quite a bit and I haven’t had the time to adjust the sources of the binding to match the new structure. Is there anything in particular you are interested in regarding the sources of the binding?

Hi Arjen (@Mephix),

The “problem” is that I don’t have the ability to fill in the IP address, it’s only the binding description. (I will post a screenshot this evening!). So it looks like the binding is “empty”.

Well, I was interested to see the source and maybe help you with the development further. Hence my question. I believe there are a lot of people using the OTGW, so this binding is a “must” :wink:


The thing is, that the bindings in the upstream repo from openhab were moved from /addons/binding to /bundles, and with it of course also the build scripts etc. So I ran into a lot of issues when creating a pull request.

Unfortunately documentation (both openhab and eclipse smarthome) is now out of date or contain broken links to examples of how to get things working… so if you can help me out by explaining how the new forlder structure works or how to migrate the binding from the old to the new structure… that would be very helpful :slight_smile:

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Hi @Mephix,

I think the reply from Markus (@mstormi) basically answers the question on how…
But I’m happy to assist in any way!

I managed to get the 0.8 version running now. Items are now being populated…So that’s really nice!


Reaction from @mstormi is definitely helpful… that tutorial wasn’t available back then… so I just need to find some time to work on it again.

Also @JdeJong , nice to see you got it working!

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I have created a new fork and migrated the sources of the OpenTherm Gateway binding according to the tutorial. Also added a new channel for fault indication.

I haven’t been able to build the project… something I need to look into.

Fixed the build issues and uploaded a new test version to the binary repo. I haven’t had the time yet to test it though…

I switched over to OH 2.5 and was glad @Mephix build the 3.0 binding. Atm works like a charm

Hi Arjen!

Thanks for this awesome plugin. Works like a charm with my Giersch Compact 100!
Just one question: If I use one of the override setpoints, how can I remove it later? Should I set it to 0 then?


Hi Frank, nice to hear you like the binding :wink:

Your question is more related to the OpenTherm gateway device itself than the binding. The OTGW website indeed states that for temporary override (TT) and constant override (TC) a value of 0 cancels the override. But I have never tested this myself.

Please let me know if it works, if not I have to look into it.


Tested today. The override for DHW works and can be removed by setting it to 0.
What doesn’t work is the override for the room temperature. But it’s not related to removing the override, it just won’t take the override at all.
It always shows the temperature of the thermostat.

I also checked the log and there only the setpoints of the thermostat is returned.

One thing that is important to know: I have two different heating circuits, one for floor heating and one for radiators in the 1st floor. Within the thermostat I can set two different setpoints. Only one is shown in the plugin.

Do I have to change anything to be able to set both setpoints through the gateway? Or at least one of the setpoints?

Thanks for your help in advance!

Hi Frank,

I am not sure how it would work with two circuits… but if the boiler has two room setpoints, that might explain why the constant or temporary room setpoint override doesn’t work. With this binding though, I am limited to the features of the OTGW device. And as far as I know, it doesn’t support overriding two separate room setpoints. At least, not with the standard firmware.

If you check the OTGW site with the link I provided earlier, you will see all the commands the OTGW device supports. Some commands are mapped to channels, like temporary and constant override, but any command not mapped to a channel can always be set through the generic “Send command” channel of the binding.

Please check if you can get the setup working with just the OTGW device and OTmonitor or telnet or something… to find out whether the issue is with the binding or the hardware.