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Hi all!

I am new to this forum. I have successfully installed OTGW last month. However, I observed some weird things in the operation with Domoticz. Hopefully someone on this forum can clarify the situation and guide me in the right direction.

First of all: I use the Nodo-shop OTGW with Wifi in combination with a Intergas HRE 28/24 boiler and a Honeywell Chronotherm Thouch Modulation thermostat.
I have succesfully added the OTGW to Domoticz 2020.2 and I am able to see all the devices. Even communication with OTGW seems to work flawlessly.
Also, normal operation via the thermostat still works as it should (I use the continues temperature setting instead of a weekly program)

Observations:
1) Delay: When I change the setpoint in Domoticz, it almost takes 2 to 4 minutes before the boiler reacts.

2) Reset: After changing the setpoint in Domoticz it is sometimes automatically resets to the value on the thermostat and the boiler switches off again. (e.g. 18.0 on thermostat --> 20.5 changed in Domoticz --> reverts back to 18.0)

3) Rounding: When changing the setpoint via a manual command on the hardware settings-page (TT=20.5 or TC=20.5), the thermostat switches to 20.0 degrees.
Do I need to use a comma in the manual command?

Did someone of you also face such behaviour? Hints are very welcome!

Regards,
Steven

StevenG wrote:Observations:
1) Delay: When I change the setpoint in Domoticz, it almost takes 2 to 4 minutes before the boiler reacts.

2) Reset: After changing the setpoint in Domoticz it is sometimes automatically resets to the value on the thermostat and the boiler switches off again. (e.g. 18.0 on thermostat --> 20.5 changed in Domoticz --> reverts back to 18.0)

3) Rounding: When changing the setpoint via a manual command on the hardware settings-page (TT=20.5 or TC=20.5), the thermostat switches to 20.0 degrees.
Do I need to use a comma in the manual command?

I'll address your observations slightly out of order:
1) In an Opentherm setup, the thermostat is the master. This means that the OTGW (acting as the slave) cannot simply tell the thermostat to change the setpoint. It has to wait for the thermostat to ask if a setpoint change is desired. Depending on how (in)frequently the thermostat asks about that (via MsgID #9), there will be a shorter or longer delay.

3) This is a quirk of the Honeywell Chronotherm Thouch Modulation, as mentioned here.

2) This is a consequence of #3. Because the Honeywell Chronotherm Thouch Modulation switches to 20.0 when the OTGW requests 20.5, the OTGW concludes after a couple of attempts to change the setpoint that the operation failed. It then gives up. This should not happen when requesting a setpoint in whole degrees.

Dear Schelte,

Thank you for your clarification on my observations.
Now I know that the thermostat is the master and the OTGW works as the slave, it makes more sense about the delays and resets!
This is now completely clear to me.

After your reply I also noticed that when the boiler is already active (heating to 18 degrees early in the morning), the thermostat sends messages more often.
It then makes sense that there was almost no delay and the reset didn't occur.

Best regards,
Steven