Use real room temperature with Homematic HG-HM-CC-RT-DN

Dear forum,

I successfully installed openhabbian on my raspberry pi 3 and got my homatic HG-HM-CC-RT-DN heating controller working with openhabian. I can read the measured temperatur and set the wanted temperature via rules and the UI.

But my problem is that in my living room there is a board over the heater so that the air is stuck a little and the HG-HM-CC-RT-DN measures really hight tempearatures and therefore I have to set high temperatures in the UI, i.e. to 24°C to achieve ~20°C. Due to the stuck, hot air, there is no real offset i could use to calculate the desired set temperature.

Because I also want to establish a presence detection via bluetooth, I came up with the idea to measure the room temperature separately by installing a raspberry pi W and connect a temperature sensor to it and use its bluetooth ability to scan for my mobile phone.

So I bought two raspberry pi W and the temperature sensors. I finally got it working. The raspberry pi W can read the temperature and, via bash script, the temperature is send to the openhab via WLAN and the REST API.

Now, I would like to use my measured temperature, acquired by the raspberry pi W, to

a) override the measured temperature of the HG-HM-CC-RT-DN


b) control the valve state by myself (with a rule).

But neither works. I used a setpoint statement in a rules file to set the valve state, but nothing happend. And I tried to use setpoint to set (override) the temperature of the HG-HM-CC-RT-DN. But that also diddn’t work. No change in the valve state.

Is there any way to let the HG-HM-CC-RT-DN know the excact temperature provided by the raspberry pi W or set the valve state by a rule? I could not find any solution for that so far. Does anyone have another idea to solve the problem? I know that is possble to link a HG-HM-CC-RT-DN with a homematic temperature sensor when a ccu is used, but I use a raspberry pi 3 with a CUL srtick.

Any help is highly apreciated!

Thanks in advance!

It’s not possible. You can’t inject the temperature. And you can’t set the valve state.

The solution is to buy the Homematic Wall thermostat kit (34,95€). Build time 5 minutes, no soldering, just clicking parts together. Works like a charm. I am running one of these in every room.

I don’t use a ccu2 as well. Homegear & Homematic Konfigurator let’s you create direct links.

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It should be possible to set an offset temperature for a HM-CC-RT-DN using the CCU UI. The offset can tell the HM-CC-RT-DN to heat until it measures a higher (or lower) temperature than the current setpoint is. E.g. if you have an offset of +2 degrees and a setpoint of 20 degrees it will heat up until it measures 22 degrees internally.

With a bit of scripting it should also be possible to set the offset via Homegear.