Baxi Slim + Honeywell Lyric T6

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wess51
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Baxi Slim + Honeywell Lyric T6

Post by wess51 »

Hello Schelte!

I'm thinking about to revisiting OTGW and have a question.

For some time, I have Baxi Slim 1300 with equipped QAA73 Thermostat out of box and I wanna replace it with something, that can be controlled remotely.
As it described on equipment matrix, QAA73 did not support ID=9, so obviously there nothing I can do with it.

So for this purpose, we bought Honeywell Lyric T6 as replacement. It has HomeKit support and OpenTherm on board.

After connecting it to OpenTherm interface and powering on, we can see flame status on boiler is working for a seconds and it stop working. After that, boiler stop to respond to any commands and only available to read stats (like monitor mode on OTGW).

So, I start researching how boiler and QAA73 talking each other. Thanks to OTGW, turns out that thermostat frequently read ID=3 slave configuration and write that configuration to ID=2 . If boiler stops receiving those messages, it will be only available only in monitor mode.

As I found, Lyric T6 only once at powering on read ID=3 and write ID=2, while for boiler in needs to be performed always.

Is there any way to make OTGW read and write those ID's, like it thermostat do?

I can help with logs, but sold my OTGW, so I can buy new one for helping.
hvxl
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Re: Baxi Slim + Honeywell Lyric T6

Post by hvxl »

Interesting, albeit strange that the boiler would need this. Are you sure that is the reason communication stops?

MsgID 3 is slave configuration. The information received should not just be copied to the master configuration, MsgID 2. In the log I have for the Baxi Slim/QAA73 combination, I see the following ID2 and ID3 messages:

Code: Select all

T90020004  Write-Data  Master configuration: 00000000 4
B40030904  Read-Ack    Slave configuration: 00001001 4
As you can see, the data bytes in the messages are different.

Sending a Read-Data for ID3 is easy. Just run the AA=3 command and the OTGW will send it periodically instead of a request from the thermostat that the boiler does not support. But ID2 should be a Write-Data request. The OTGW currently only has support for sending a few specific Write-Data requests. The Master configuration is not one of them. But maybe sending a Read-Data may be enough.
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wess51
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Re: Baxi Slim + Honeywell Lyric T6

Post by wess51 »

hvxl wrote: Sat Apr 16, 2022 10:36 pm Interesting, albeit strange that the boiler would need this. Are you sure that is the reason communication stops?

MsgID 3 is slave configuration. The information received should not just be copied to the master configuration, MsgID 2. In the log I have for the Baxi Slim/QAA73 combination, I see the following ID2 and ID3 messages:

Code: Select all

T90020004  Write-Data  Master configuration: 00000000 4
B40030904  Read-Ack    Slave configuration: 00001001 4
As you can see, the data bytes in the messages are different.

Sending a Read-Data for ID3 is easy. Just run the AA=3 command and the OTGW will send it periodically instead of a request from the thermostat that the boiler does not support. But ID2 should be a Write-Data request. The OTGW currently only has support for sending a few specific Write-Data requests. The Master configuration is not one of them. But maybe sending a Read-Data may be enough.
Thanks for reply (wow!)

Yeah, very strange why Baxi realize this, only thinking about looks like vendor lock.

Why am sure about this, because i found a project on arduino, where developer points that on baxi slim it should "spam" those messages on OT. That's double confirm my theory.

I can't remember what i trying with OTGW with those messages, it happened years ago, so only what i can get from my memory.

It can be easier, if i have OTGW right on my hand, but as i described, it takes some problems...

As a developer described, thermostat should read data from ID=3 and write same in to ID=2.
hvxl
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Re: Baxi Slim + Honeywell Lyric T6

Post by hvxl »

It would have been helpful if you had provided a link to the project you are referring to. Now I have to take your word that the developer says to copy the data from ID3 to ID2, which seems nonsense to me.

Anyway, the OTGW doesn't currently have a feature to send a Write-Data request for ID2 to the boiler. It can possibly be made. But you indicated that you don't have an OTGW anymore. So I'm unclear about what you are trying to achieve with this line of questioning.
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wess51
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Re: Baxi Slim + Honeywell Lyric T6

Post by wess51 »

hvxl wrote: Mon Apr 18, 2022 8:52 pm It would have been helpful if you had provided a link to the project you are referring to. Now I have to take your word that the developer says to copy the data from ID3 to ID2, which seems nonsense to me.
You can find a mention about this there http://arduino.ru/forum/programmirovani ... ent-474907

Raw translated by Google, but I think its enough for understand. Also, he mentioned at first post, that he has Baxi Slim.
In total, 10-12 seconds remain for the complete data processing cycle. The original code of the author's library http://ihormelnyk.com/mqtt_thermostat uses a third less resources. but there is less data. About the code with ID2, that it can be done in setup(), it doesn’t run, and without it, my boiler is only monitored, but it will send the code once every 50 seconds completely (here you need to dig into the info, the numbers 40 and 20 seconds appear). The ID3 OT mode is turned off, the thermostat only monitors and that's not all. Other boilers are on the drum. In any case, the library itself is FROM addressing issues.
hvxl wrote: Mon Apr 18, 2022 8:52 pm Anyway, the OTGW doesn't currently have a feature to send a Write-Data request for ID2 to the boiler. It can possibly be made. But you indicated that you don't have an OTGW anymore. So I'm unclear about what you are trying to achieve with this line of questioning.
I should have start this topic years ago, but I'm made up for this conversation only now. Buying a new one from NodoShop not a problem for this.
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Re: Baxi Slim + Honeywell Lyric T6

Post by hvxl »

This message seems to more closely represent your statement.

Roughly translated:
I repeat, it is necessary that the boiler would give the thermostat a code with MsgID=3 (R) and this code should be written by the thermostat to MsgID=2 (W). In my case, I first read MsgID=3 (in general, and for good, you would first need to monitor all MsgIDs and calculate those available for your boiler and work with them in the future if necessary), then send this code back to the boiler, but already in MsgID=2 (in my last code it's lines 449-451).

If you make a universal thermostat for any OT boilers, then MsgID=3 and MsgID=2 should work in pairs, I didn’t set such a goal for myself.
If you look at the code, he only copies the low byte, which is a little better than copying the full data, but it's still nonsense.

In general, I don't get the impression that this person has a firm grasp of the opentherm protocol. Claiming that MsgID 3 and MsgID 2 should work in pairs is something he must have made up himself. There is no basis for this in the opentherm specification. It also doesn't match what the QAA73 thermostat does. There can be minutes between MsgID 3 and the subsequent MsgID 2.

So, the Baxi slim boiler only wants to work with specific thermostats. That means that MsgID 2 has to contain a MemberID code that it accepts. MemberID code 4 (Siemens) is one (and maybe the only one) that works. The Baxi slim boiler also reports 4 as its own MemberID code. That doesn't mean that the value has to be copied. MemberID codes are normally hardcoded constant values that specify the manufacturer of the boiler or thermostat.

So I suspect that a feature that can send a specific MemberID code in MsgID 2 should be enough to fool the Baxi slim boiler. It probably doesn't need MsgID 3 at all. But just to be clear, such a feature doesn't currently exist in the gateway firmware. Of course, using the interface firmware, you can send any message you like.
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Re: Baxi Slim + Honeywell Lyric T6

Post by HarperCZ »

Hi!
Were you able to resolve the issue? One year later and it looks like I'm having similar issue :)

I have Enbra CD34H boiler in combination with Tado termostat. All seems to work, but when using Tado, boiler is for some reason not modulating flame, then it overheats and turn off flame for few mins as a failsave.

I was comparing opentherm communication between wokring thermostat and Tado and only difference I noticed was mentioned ID 2 writes and ID 3 reads. There is no correlation between those two I could see, so I believe all I need to do is to write memberID to the boiler. As I understood this is not possible with current implementation of otgw and interface fw would need to be used. But this would require some more logic to forward messages.

I've tried to get in touch with Tado if this possible to implement on their side, but in the meantime I was curious if you were able to solve this other way.

Thanks!
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Re: Baxi Slim + Honeywell Lyric T6

Post by hvxl »

It is not logical that the symptoms you report are due to the member ID the thermostat sends in MsgID 2, unless the boiler is deliberately sabotaging communications with any but its own brand of thermostats. But in that case I would expect it to simply refuse to communicate, not to alter its behavior in such a subtle way.

It seems more likely to me that you may have missed some important detail when comparing the logs of the working thermostat and the Tado.
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