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OTGW plugin - odd behaviour
Posted: Wednesday 14 January 2026 18:21
by manjh
I moved from my old Domoticz/Raspberry installation to a new setup, and also installed OTGW.
It works, but for some strange reason I see odd values, for instance the "Return water temperature" is fixed on 0 degrees.
I can see in the devices tab that it is updated regularly, and I am quite sure the return pipe is hotter than zero.
What could be wrong here?
In the old setup there was a more valid value!
Re: OTGW plugin - odd behaviour
Posted: Wednesday 14 January 2026 19:47
by waltervl
What does Domoticz log say when a value is received?
From what version of Domoticz did you upgrade. The firmware of OTGW in newer Domoticz versions needs to be min 5.x
https://wiki.domoticz.com/Opentherm_Gateway_OTGW
Re: OTGW plugin - odd behaviour
Posted: Wednesday 14 January 2026 21:32
by manjh
Log doesn't say much:
Code: Select all
2026-01-14 21:29:26.459 OTGW: Temp (Return Water Temperature)
As for firmware, I guess it's pretty old. I must have the OTGW for many years now, no idea how many....
Is there a simple way to find the firmware version?
Re: OTGW plugin - odd behaviour
Posted: Wednesday 14 January 2026 21:50
by manjh
My OTGW carries an ESP unit to communicate with the Domoticz server. When I log on and look at the log, I see:
Code: Select all
v14078825 : Ser2N: serial buffer full!
What does this mean?
Re: OTGW plugin - odd behaviour
Posted: Thursday 15 January 2026 11:47
by waltervl
That the serial communication to Wifi is not working correctly. But better check that with OTGW specialists...
Re: OTGW plugin - odd behaviour
Posted: Friday 16 January 2026 7:43
by azonneveld
manjh wrote: Wednesday 14 January 2026 21:32
Is there a simple way to find the firmware version?
Use the OTMonitor to connect to your OTGW. Using that tool you can also update your otgw firmware.
https://otgw.tclcode.com/download.html (near the bottom of the page)
Re: OTGW plugin - odd behaviour
Posted: Monday 19 January 2026 7:12
by manjh
azonneveld wrote: Friday 16 January 2026 7:43
manjh wrote: Wednesday 14 January 2026 21:32
Is there a simple way to find the firmware version?
Use the OTMonitor to connect to your OTGW. Using that tool you can also update your otgw firmware.
https://otgw.tclcode.com/download.html (near the bottom of the page)
I installed the tool. When I connect to the OTGW, all I see is a message like this:
To make sure, I also disconnected the HW in Domoticz, does not mke a difference. When I keep the HW enabled, I can see error messages in the log, so the OTMonitor is connected...
Re: OTGW plugin - odd behaviour
Posted: Thursday 22 January 2026 22:20
by azonneveld
I installed the tool. When I connect to the OTGW, all I see is a message like this:
To make sure, I also disconnected the HW in Domoticz, does not mke a difference. When I keep the HW enabled, I can see error messages in the log, so the OTMonitor is connected...
Okay, so your connection is established, but not working.
I dont recognize that code but it seems to be a problem with de OTGW or ESP.
Try a powercycle on the OTGW, if that doesnt work, try reloading (or update) the ESP firmware.
Re: OTGW plugin - odd behaviour
Posted: Friday 23 January 2026 23:53
by manjh
azonneveld wrote: Thursday 22 January 2026 22:20
I installed the tool. When I connect to the OTGW, all I see is a message like this:
To make sure, I also disconnected the HW in Domoticz, does not mke a difference. When I keep the HW enabled, I can see error messages in the log, so the OTMonitor is connected...
Okay, so your connection is established, but not working.
I dont recognize that code but it seems to be a problem with de OTGW or ESP.
Try a powercycle on the OTGW, if that doesnt work, try reloading (or update) the ESP firmware.
I already tried re-booting several times over the past weeks.
But why would that work I can see many valid values coming into Domoticz from the same device. Connecting from the Windows OTMonitor does not yield anything. And yes, I did disconnect the Domoticz HW entry before trying that.
Re: OTGW plugin - odd behaviour
Posted: Sunday 25 January 2026 17:28
by azonneveld
manjh wrote: Friday 23 January 2026 23:53
I already tried re-booting several times over the past weeks.
But why would that work I can see many valid values coming into Domoticz from the same device. Connecting from the Windows OTMonitor does not yield anything. And yes, I did disconnect the Domoticz HW entry before trying that.
What firmware are you running on your ESP? (espeasy, tasmota, etc?)
What does the webinterface of the ESP shows you?
Re: OTGW plugin - odd behaviour
Posted: Monday 26 January 2026 10:09
by manjh
azonneveld wrote: Sunday 25 January 2026 17:28
manjh wrote: Friday 23 January 2026 23:53
I already tried re-booting several times over the past weeks.
But why would that work I can see many valid values coming into Domoticz from the same device. Connecting from the Windows OTMonitor does not yield anything. And yes, I did disconnect the Domoticz HW entry before trying that.
What firmware are you running on your ESP? (espeasy, tasmota, etc?)
What does the webinterface of the ESP shows you?
It runs ESPEasy, build 147.
Not sure what you mean by the Web interface. When I log on to the unit from a browser, I can see the usual info. THe one thing that stands out is the errors in the log:
Code: Select all
1020965753 : Ser2N: serial buffer full!
Re: OTGW plugin - odd behaviour
Posted: Wednesday 28 January 2026 7:18
by azonneveld
manjh wrote: Monday 26 January 2026 10:09
It runs ESPEasy, build 147.
Not sure what you mean by the Web interface.
Code: Select all
1020965753 : Ser2N: serial buffer full!
Webinterface: open browser, enter <ESP-IP:80>.
You should see a webinterface.
That might provide some log (not sure on the old version).
If not, you can upgrade the firmware of your ESP using
https://td-er.nl/ESPEasy/ (Chrome/Edge only)
(take out the esp of your OTGW, connect to computer)
Or: perhaps consider buying a new OTGW, which has lots of improvement:
https://www.nodo-shop.nl/nl/ons-assorti ... ilder.html
Re: OTGW plugin - odd behaviour
Posted: Wednesday 28 January 2026 12:03
by manjh
Thanks, that webinterface is the one I was using.
Upgrading the ESP software sounds OK, except that I run the risk of an inoperable OTGW, which makes my heater go down. (Complex story, has to do with the combination of an Insmart remote monitoring tool with the Honeywell T6 thermostat, Known problem, Insmart is working on it).
I guess going for a new OTWG device sounds safe. I will check with Remco.
Re: OTGW plugin - odd behaviour
Posted: Friday 06 February 2026 16:54
by manjh
OK, I am now the proud owner of a brand-new OTGW unit.
Works great, but I have a question about the "Return water temperature".
In Domoticz a temperature device shows up, with value 0 celsius, not a very likely value compared to tht Boiler water temperature of 33,1 celsius.
You'd expect something higher than 20.
On the OTGW, I use a LAN interface, and loaded the special OTGW firmware written by Robert van den Breemen.
When I look at the values that this unit receives, the return water temperature is not in the list at all!
So where does this device come from? Is it made up by the OTWG plugin?
Re: OTGW plugin - odd behaviour
Posted: Friday 06 February 2026 22:57
by azonneveld
manjh wrote: Friday 06 February 2026 16:54
So where does this device come from? Is it made up by the OTWG plugin?
Nice that your new device is working!
Return water temperature is one of the normal outputs of the OTGW. But since no data is given by your boiler, it remains zero.
RWT is not an output for every boiler.
Maybe your boiler is included in the
matrix.
That indicates what data is available for each device.
Perhaps your device can also present the
waterpressure
Re: OTGW plugin - odd behaviour
Posted: Saturday 07 February 2026 8:43
by manjh
azonneveld wrote: Friday 06 February 2026 22:57
manjh wrote: Friday 06 February 2026 16:54
So where does this device come from? Is it made up by the OTWG plugin?
Nice that your new device is working!
Return water temperature is one of the normal outputs of the OTGW. But since no data is given by your boiler, it remains zero.
RWT is not an output for every boiler.
Maybe your boiler is included in the
matrix.
That indicates what data is available for each device.
Perhaps your device can also present the
waterpressure
Water pressure is there, return water temperature is not. The matrix shows X...
Re: OTGW plugin - odd behaviour
Posted: Thursday 12 February 2026 20:59
by azonneveld
manjh wrote: Saturday 07 February 2026 8:43
return water temperature is not. The matrix shows X...
Was it there before you upgraded?
Re: OTGW plugin - odd behaviour
Posted: Thursday 12 February 2026 23:06
by manjh
It was there, but had a very strange value (over 100 degrees)...
Re: OTGW plugin - odd behaviour
Posted: Sunday 15 February 2026 15:52
by azonneveld
For measuring the boiler's in and out temperature, I use an ESP with DS18b20 sensors, tie-wrapped to pipes.
You can attach multiple sensors to 1 ESP.
https://espeasy.readthedocs.io/en/lates ... 18b20.html
Re: OTGW plugin - odd behaviour
Posted: Sunday 15 February 2026 16:48
by manjh
I know, I have used ESP based temperature sensors quite a bit, but now moved to Zigbee sensors.
But it is actually a good idea, I think I still have one ESP lying around somewhere with three DS18B sensors. I'll install them later this week.
Again, good idea, thanks for bringing it up!