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Hello Shelte,

otmonitor has a glitch when displayng the relative modulation level (please see pictures below).

It only happens when the thermostat tries to write msgid17

When reading msgid17, the value gets displayed correctly.

Also, when the boiler is running, relative moulation level costantly jumps between 8% (real value reported by the boiler) and 100% (value that the thermostat tries to write).

Any ideea how to prevent that.

Thanks!

George

george wrote: ↑Tue Oct 17, 2023 6:27 pm It only happens when the thermostat tries to write msgid17

That is a violation of the Opentherm specifications. MsgID 17 only allows Read operations.

(My name is Schelte, by the way.)

Hello Schelte,

is there a way I can go around this?

I tried using UI=17 command but it does not work and this is what i get:
15:25:44.270072 T90110000 Write-Data Relative modulation level (MsgID=17): 0.00
15:25:44.329952 BF0110000 Unk-DataId Relative modulation level (MsgID=17): 0.00

I thought that if I mark it as unknown UI=17, I can then use AA=17 to get a read like below.
example for UI=98 and AA=28:
15:25:33.000247 T10620000 Write-Data RF sensor status information (MsgID=98): 0 0 0 0
15:25:33.001117 R801C0000 Read-Data Return water temperature (MsgID=28): 0.00
15:25:33.358582 B401C2400 Read-Ack Return water temperature (MsgID=28): 36.00
15:25:33.359503 A70620000 Unk-DataId RF sensor status information (MsgID=98): 0 0 0 0


I used UI command on other unknown data id's and all was fine (except for msgid 14 and 17); any ideea why?

thanks and sorry for misspelling your name!

George

The UI command tells the OTGW never to send the specified message to the boiler. That's the opposite of what you want, and possibly detrimental to the temperature control algorithm of your thermostat.

The error is really in the thermostat that sends an invalid message. Since it is probably not feasible to get this fixed on the thermostat side, I guess a possibility is to put more knowledge into OTmonitor; make it ignore a Write-Data message for MsgID 17. Adding this knowledge to the OTGW itself seems a waste of resources to me.

well since the thermostat sends an invalid message there will be no difference if I stop the boiler from getting msgid17.

The problem is that nothing happens when I use UI=14 and UI=17 - it works perfectly fine for any other msgid.

Is there any reason as to why this happens?

The control algorithm will not be affected because it is based only on adjustment of the control setpoint (the boiler doesn't accept msgid14 even though the pcb manual specifically says it does)

You are right about no chance to get it fixed on the thermostat manufacturer side and changing the otgw firmware will be too much of a hassle;
that is why I hoped using UI=17 and AA=17 would solve the problem in a easy and simple way.

The opentherm specification defines a few messages as mandatory. This includes 14 and 17. The OTGW will always continue sending these IDs.

okay, thanks for clarifying that!