room temperature drops to -40

This Forum is about the Opentherm gateway (OTGW) from Schelte

Moderator: hvxl

Post Reply
rudydewit
Starting Member
Starting Member
Posts: 2
Joined: Tue Jul 06, 2021 7:33 pm

room temperature drops to -40

Post by rudydewit »

Hello,

I have a problem with the room temperature reading from the thermostat. multiple times a day the room temperature drops to -40 and this gives strange readings into domoticz graphs.
Also, the time that I get a room temperature reading is just a few times every hour, maybe 4 times and not a consistent time frame.

Is this normal? and would it be possible to get the room temperature (MsgID24) more times every hour. like every 5 min or so.

I have an Remeha iSenseRF V28 (25-09-2013) thermostat and running otgw 5.1.

19:26:39.649482 T90181A97 Write-Data Room temperature (MsgID=24): 26.59
19:26:39.819919 B50181A97 Write-Ack Room temperature (MsgID=24): 26.59

19:30:31.027000 T9018D800 Write-Data Room temperature (MsgID=24): -40.00
19:30:31.194429 B5018D800 Write-Ack Room temperature (MsgID=24): -40.00

19:31:11.971142 T90181A97 Write-Data Room temperature (MsgID=24): 26.59
19:31:12.124867 B50181A97 Write-Ack Room temperature (MsgID=24): 26.59


thanks all!
hvxl
Senior Member
Senior Member
Posts: 1965
Joined: Sat Jun 05, 2010 11:59 am
Contact:

Re: room temperature drops to -40

Post by hvxl »

-40 differs in so many bit positions from the surrounding room temperature messages that it seems unlikely that this is caused by a transmission glitch. Apparently that is really what the thermostat sends. This conclusion is reinforced by the fact that you see the same strange value on multiple occasions. You did not indicate how the information gets from the OTGW to Domoticz, but maybe you can filter out such obviously wrong values somewhere along the way. If Domoticz is polling the OTGW directly using the PS=1 command, you may need to make modifications to the Domoticz OTGW module.

Regarding the frequency of messages: In an Opentherm system, the thermostat is the master. It solely decides which messages are exchanged and in which order. The protocol provides no way for a slave (like the OTGW) to request a specific message. The Remeha Celcia 20 thermostat has an usual feature that a slave can send a response with a different MsgID than the request and the Celcia 20 then requests that message. At least for MsgID 4. I don't expect the ISenseRF will do the same as it has completely different firmware. But if you are curious, you can try it with the OTGW interface firmware.
Schelte
rudydewit
Starting Member
Starting Member
Posts: 2
Joined: Tue Jul 06, 2021 7:33 pm

Re: room temperature drops to -40

Post by rudydewit »

Thanks for some info on this.

I will try to find a way to filter the result on the domoticz side
Post Reply

Return to “Opentherm Gateway Forum”