Recommendable wired heating control system

So basically, you are saying, you can only use Velbus temperature probes with the Velbus system. You can not tell the Velbus system from the outside, what the temperature is.



I see where the confusion is…

There’s no such thing as a “Velbus Temperature Probe”, the temperature sensor is built into the glass panels.

So unfortunately, your absolutely correct.

The best the Velbus system could offer in this situation is something I explored some time last year (I’ll try to find the thread).

You could put a 1Kohm thermistor at the end of each cable run into each zone and hook up 4 sensors to a 4 channel VMB4AN input device, which has extremely similar functionality to a thermostat (as in 4 different target points and the ability to affect relays etc)


Here’s the other thread where we explored this as a solution

The issue I am having is, that
a) this is an old building, with old walls, which was completely refurbished about 15-20 years ago.
b) i have cat5e wiring in every room … but they don’t go to the press. They go to an entire different place of the building
c) i’m not going to run new cables across the place, unless they replace an existing run. It’s extremely cumbersome.
d) I already have 100% wifi coverage, zigbee and dect coverage around the place
e) I already have DECT temperature probes in most rooms, which are fully integrated in OpenHAB.

So all I would need to achieve is to read out that temperature and push it to some sort of input, where the Velbus system can react to it.

The VMB4AN module sounds like one step in the right direction.


Arrr, again you can’t push a value into a VMB4AN, you can only read the values, or the output states that the logic inside the VMB4AN decides.

Not really, because of the above.

However… Not to be outdone…

There’s no reason why the Thermostat logic can’t be done in a stand alone openHAB2 / Node-RED instance and push relay status updates into Velbus relays. (Or any other brand for that matter)

It wouldn’t be my first choice, but there are plenty of examples of people using openHAB2 as Thermostats with very advanced timings.

@ThomDietrich Thermostat boilerplate would be an excellent start.

Alternatively, if you want a stand alone Thermostat, where you can create timings per zone and use the Thermistor option, you could do a lot worse than use a Robot Electronics DScript based Ethernet LAN relay board and expand their example Thermostats timer script (in the zip file) to cover as many zones as the relay board can support. (If you’re prepared to explore their programming language, which looks a lot like old school BASIC)

For example, the 2 relay version has 2 inputs for thermistors.

Or the 4 channel version, which has 4 inputs that you can use with thermistors.

The 8 relay version has 7 inputs, but if you wanted to switch 7 pumps and 1 boiler / heat source, based on 7 zones, it could work really nicely.

But if you just want to use the room temperature data from your existing devices, with openHAB2 taking care of the logic, you could opt for a simple Ethernet relay board like this

Which has a nice case

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Doesn’t quite work like that.

Essentially, what I want is a standalone system, that operates autonomously. Lets say, the OpenHAB board was not around, it would operate of what’s there. (Velbus relays and Velbus glass panel sensor).

However, when the OpenHAB logic is there, it would be nice to feed extra data in for an more optimised approach.

I guess, in theory, that can be achieved by manipulating the setpoint then.

Lets say, where the Velbus sensor is, it’s colder than the setpoint, but other rooms in the zone have achieved the temperature needed. Or the opposite.

The VMB4AN module is interesting non the less, because it would allow for the Velbus system to control and monitor the temperature of an immersion boiler.

It would also allow to measure the temperature of the hot return feed and only turn the heating boiler on, when that temperature drops there, even though the zone circulation pumps already are on.


Right then…

I see where you’re going with this.

So yes, a combination of Glass Panels and 1K sensors via VMB4AN would do the trick.

I will use this system.

Möhlenhoff alpha 2 Ethernet Bus or Funk

You can read and write Temperature with HTTP binding and
I haven’t tested it jet but the Manual is quite comprehensive.


  1. it has virtual Thermostats where you can use external Roomtempratures from Openhab
  2. with virtual thermostats if Openhab dies and the station gets no new temperatures for the Room it changes to emergency operation.
  3. you can change the setpoint at the thermostat and in Openhab
  4. Pump connection
  5. Boiler connection
  6. OEM of Homatic ip

Official Instructions and XML Guide :

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In case anyone is watching this thread, or finds it later.

The Robot Electronics DScript boards with the thermostat and timer script can work totally independently, other than pulling current time from an NTP.

With openHAB2 able to push target temperature updates and switch on and off time sections. (If that’s what you allow / program into the script, {script is maybe the wrong word, as it creates a full web page UI})