Equipment detailsWhile shopping for Opentherm equipment with home automation in mind, it can be useful to have some idea to which extent boilers and thermostats support the opentherm protocol. Only some messages are mandatory (ID's 0, 1, 3, 14, 17, and 25), all others may or may not implemented. (Yes Daalderop, support for MsgID 14 is mandatory.)
For home automation it is important to buy a thermostat that supports MsgID 9 (Remote override room setpoint) and possibly MsgID 100 (Remote override function). It may also be nice to get a boiler that supports MsgID 18 (CH water pressure).
Unfortunately this type of information is not usually provided by the manufacturors. That's why I started compiling a matrix with information extracted from logs of the opentherm communication between thermostats and boilers provided to me by Opentherm Gateway owners.
Of course, the fact that equipment returns a value for a certain MsgID doesn't always mean it really supports it. For example, I have heard that the Intergas boiler may respond to MsgID 18 (CH water pressure) with a value of 6. Clearly that is totally bogus. The valid range of values is only 0 to 5. 6 bar would definitely not be good for a central heating system.
Another example: the Remeha iSense sends MsgID's 20, 21 and 22 with its current time and date information, but it ignores whatever values it gets back in the response, unlike the Honeywell chronotherm IV. As a result, the Opentherm Gateway is not able to change the clock on an iSense thermostat.
For the reasons mentioned above, I obviously cannot give any guarantees on the information provided below. It's a best effort attempt to provide some more details on Opentherm equipment than are readily available from other sources. However, I can not be held responsible if information in these tables turns out to be less than accurate.
If your equipment is missing from the tables below, please add it by uploading an otmonitor log file.
Clarification of the tables
- A bullet (●) next to a DataID in the thermostats table means the thermostat has been observed to send the specified DataID.
- A bullet (●) next to a DataID in the boilers table means the boiler responded with a Read-Ack or Write-Ack message to a request from the thermostat for the corresponding DataID.
- A cross (×) means the boiler responded with an Unknown-DataID message to a request from the thermostat for the corresponding DataID.
- A question mark (?) indicates that logs have been uploaded with conflicting results for the DataID.
- If there are very few bullets listed for a boiler, that does not necessarily mean that the boiler has very limited Opentherm support. If there are also very few crosses, the boiler was probably used with a thermostat that doesn't send many different Opentherm DataID's. Only a large number of crosses indicates poor Opentherm support by the boiler.