Adding new ID to opentherm communication

HarperCZ

Hi,

I'm facing issue when my boiler is not behaving properly when using Tado thermostat (boiler is not modulating flame).

After some extensive troubleshooting I found that issue is most likely in opentherm communication, more specifically, in missing message ID 2 (Master configuration).

From what I saw comparing communication between working thermostat and Tado thermostat using opentherm gateway, only difference is that supported thermostat is periodically reading ID 3 Slave configuration and writing to ID 2 Master configuration.

I believe that what boiler need is actually Master MemberID code to be set in ID 2 second byte.

I know this is not mandatory by opentherm specs, but it looks like quirk of my boiler, but is it possible to setup this to be sent as well from Tado? I would hate having to give up opentherm modulation because of this.

If needed, I can get logs from opentherm communications from both supported and unsupported thermostat if that will help to add official support for my boiler (Enbra CD 34h).

Thanks for any help!

HarperCZ

Hi, I just wanted to post update in case anyone will face same or similar issue.

Tado support was able to set Master MemberID, but that haven't solved problem.

Issue is that Tado is sending message ID 14 "maximum relative modulation level" every 6s which is too often for my boiler and it prevents it from modulating flame.

I would need to tweak this interval to 2mins which is unfortunately not possible right now. Here is feature request support directed me to create:

Make Opentherm boiler specific tweaks possible — tado° Community (vanillacommunities.com)

Anyway it's now working with workaround where I'm filtering out Tado ID 14 messages and passing only changes to boiler with opentherm gateway.

johnnyp78

You’d probably be better off contacting Tado directly about this. There might be a way of modifying the signal with an opentherm gateway but I don’t know enough about it.