Workaround for missing 'remote override room setpoint'

[tiscjo]

Hi,

I have since a few weeks an OTG, the monitor software is running on a Linux machine, almost everything works beautifully, many thanks to Schelte!

My only problem is what several people mentioned here in the forum: my thermostat (QAA73) does not allow MsgID 9 (remote override room setpoint), so I can not set the heating higher or lower from a remote site.

I have an idea for a workaround and want to ask if it would be feasible in the firmware:
One could submit an offset value to the OTG and OTG would always apply this offset (added in one direction, subtracted in the other direction) when the thermostat and the boiler communicate about room setpoint.
For example: with an offset -2.5 one would achieve that no matter what the thermostat outputs as room setpoint, arrives at the boiler always 2.5 degrees less. On the way back, when the boiler will confirm the value, the offset is subtracted, so it is apparently 2.5 degrees more, which is exactly the value that the thermostat wanted.
If the offset value is 0, then the conversation remains unaltered.

Or: can you achieve something similar with the currently existing commands? I have read everything on otgw.tclcode.com several times, but found no solution.

[hvxl]

While it may be possible to implement this in the firmware, I don't expect it will do you any good. Boilers aren't (supposed to be) taking any action based on the room setpoint.

If you look at the equipment matrix you will see that some thermostats don't even bother to send the room setpoint. And if they do, several boilers respond with Unknow-DataID.

And that's OK because the parameters that have been defined in the opentherm spec for the thermostat to control the boiler are the Control Setpoint and Maximum Modulation. There are commands available in the OTGW to manipulate those two parameters.

[tiscjo]

Hi Schelte,

sorry for my lately response and many thanks for your answer!
You helped me a lot. I was on the wrong path.
Your OTG is a fine piece of hardware and software.

[poefi]

Hello from Belgium,

Since sunday I have total control over the qaa73 from anywhere at anytime.

2 weeks ago I was a happy user of the OTG superb hardware and software created by Schelte; thank you very much for sharing your magnificent project.
My goal was to remotely control my qaa73 using a remote control or my smappee to control electric applicances from anywhere at anytime (supports the 433MHz home automation protocol).
My plan was to built a arduino based 433MHz receiver that should translate the room setpoint requests to OTG TT or TC commands.
My happiness did not last for long as I was confronted with the absence of the remote override room setpoint support by the qaa73.
After a long sniff, a good brainstorm, buying a 6 wire cable and optocouplers, a lot of hard labor I succeeded to fulfill my dream.

How do I did it :
The clue is that the qaa73 has a day/night switch and a Alps rotary encoder with 2 switch outputs. The behavior of the switches can easily taken over by a microprocessor.
I soldered the 6 wires to the qaa73 : 1xgnd, 2xrotary encoder, 1xday/night switch, 2x opentherm.
The otherside of the wires are connected to a breadboard supporting the arduino micro-pro board, the 433MHz receiver( too cheap, much troubles to have good reception ), optocouplers. Finally the arduino is connected to the OTG( opentherm and the otwg tx line ).
After some hours building, writing and testing I did succeed to master the qaa73 to set remotely the room temperature setpoint at 18,22 or 23,5°C ( day mode ) or 14°C (night mode).
If you wish I can post some pictures ( probably Thursday ).

[tiscjo]

Hello poefi,

these are good News! Can you please post more infos about the electrical installation?

Thanks in advance!

[tiscjo]

Before I tell you about my experience with the commands CS, MM and HW, I would like to describe, why do I need the whole thing.

I am really pleased with the cooperation of my thermostat and the boiler, except during holiday periods. At the thermostat can be specified the holiday season with a start and end date, but that works not always reliable and the method is not flexible enough. Sometimes the holiday lasts shorter or longer. I can access my computer at home over ssh, so I wanted to have a way to remote control the heating and hot water production. It is also important that the thermostat is not separated, as it would after some time forget all settings and on the other hand it supplies the room temperature, wich is still needed.

The big question was this: what happens when the thermostat with its program remains online and OTG monitor intersperses other values?

I tried it and it works perfectly! The monitor works like a man-in-the-middle and modifies the informations in both directions.

For example: the thermostat will have hot water, but I sent 'HW=0' to the monitor. Now it looks in the log like this:
09:08:32.655474 T80001300 Read-Data Status: 00010011 00000000
09:08:32.667225 R00001100 Read-Data Status: 00010001 00000000
09:08:32.982477 B4000112A Read-Ack Status: 00010001 00101010
09:08:32.993275 AC000132A Read-Ack Status: 00010011 00101010

Or: the thermostat will achieve higher room temperature and will adjust CS to 80, but I have decided against it with 'MM=100' and 'CS=20'. Then in the log:
09:08:33.653472 T10015000 Write-Data Control setpoint: 80.00
09:08:33.664531 R10011400 Write-Data Control setpoint: 20.00
09:08:33.980500 BD0011400 Write-Ack Control setpoint: 20.00
09:08:33.991478 AD0015000 Write-Ack Control setpoint: 80.00

So it's easy to overtake the control of heating permanently or temporarily.