Homey Community Forum

How to link thermostat with external thermometer

Hello,
I just changed my fibaro controller with Homey pro.
In fibaro I used feature called “linked devices” which allowed me to link external thermometer with thermostat which controls my electric underfloor heating. I can’t seems to find something similar feature in Homey pro. Is this somehow possible?
The reason I’m trying to link these two devices is because the location of the actual thermostat is not very good for measuring the room temperature, the internal thermostat sensor is affected by the location and does not show a valid room temperature.
So I bought fibaro smoke sensor which also show the temperature and installed it on better place.
In fibaro when I linked these 2 devices, fibaro was controlling the thermostat based on the temperature from the external sensor rather than internal thermostat sensor.
Is this possible in Homey Pro as well?
Also, what heating schedule app would you recommend?

Thank you
Peter

Use virtual device (thermostat) that will be assigned with temperature from external sensor via flows. And based on this virtual thermostat state you can controll your heating via flows as well.
Second option is to use flows directly, but you will loose option to change target temperature comfortably via virtual device (you will need to adjust flow or logic variable if used).

How should the electric underfloor heating be controlled exactly?
Can you give an example?
Air temperature, temperature of electric floor heating, outside temperature, possibly times and seasons?

I don’t use a heating plan app, so I couldn’t recommend an app.

Please see an example of heating plan:

Monday - Friday - Living room/Kitchen
Between 6am-8am turn heating to 22C (getting up, breakfast)
between 8am - 4pm target temperature 20 (at work)
4pm - 10pm - target temperature 22C (back from work)
10pm - 6am - target temperature 19C

And so on for each zone and day/weekend.

Thank you for suggestion.
I installed the VThermo app but can’t see any way to add the devices (external temperature sensor and thermostat) to this virtual thermostat.
Is this (VThermo) the virtual thermostat you suggested or there is some other app?

Thank you
Peter

Install this app Virtual device: https://homey.app/en-us/app/com.arjankranenburg.virtual/Virtual-Devices/

Then add device, select this app and select thermostat. Then you need to make flow that will assign temperature from sensor to this device.

Ok, so this is a typical heating plan.
Which thermostat do you use? At some thermostat you can set an temperature offset or calibrate them, e.g. HeatIt Z-TRM 3.
This should be the easiest way without any additional apps or flows.

Yes, pretty much typical heating plan. Is there any good heating plan app I could use?

I’m using the Heatit Z-TRM2fx and it is possible to set the offset but the offset is not constant so that would not work unfortunately.

Thank you
Peter

There are 3 apps I know. But I didn’t try them myself.
So if you are not satisfied with these apps let us know and I guess we will find a solution:

The way @Igy suggested could also be a solution. I also switched for more than a year from Fibaro to Homey and some things are not always self-explanatory at first sight. So maybe give them a try.

Just to add, it took me a while ago to find out how to assign temperature to virt. thermostat over the flow. Create flow “when external temperature on sensor change” then “set a virtual sensor value” on your newly added virtual thermostat. When creating thermostat over VD, dont forget to select corect capabilities for it (measure temperature, target temperature).
To asign temperature value to virtual sensor, you have to type in “measure_temperature” in sensor field, not to chose it from list!


In value, you select tempretaure of your external sensor.
And thats it.
Then you create 2 flows to control heater. One is applied when sensor temperature is changed and second when target temperature on virtual thermostat is set. Example of flow:

Thank you for your help. I will give it a try.

They told me this is a smart user friendly system :smiley:

It is, you just need to get used to it😉. I moved from Fibaro and no regrets. Once you understand how to work with flows, logic, different aps etc. you will be able to do almost anything in short time. And no Lua code needed at all as was needed in Fibaro in my case.

For me, Homey is also much more user-friendly than Fibaro. But Homey goes a different way. You have to understand this way first.
If you have any questions, just ask…

Is it always so difficult to include new devices to Homey network?
With Fibaro I used to use NWI (network wide inclusion) and managed to add devices which were on completely different floor without problem. But with Homey I have to have the controller right next to the device when including. If it is just little bit further away (3-4m) the inclusion either fails or the device is added but most parameters are not working.
Is that normal or Am I doing something wrong?
I did not even manage to test the virtual termostat and heating plans yet as I’m still struggling with adding the devices into the network.
Thank you
Peter

I did antena mod and dont have this issue. Im able to include zwave device from 2nd floor 6 meters from Homey behind 2 walls.
But yes, compared to Fibaro, zwave inclusion need to have homey not far away (without modified antena). Once included, it will use mesh for communication.
Just use power bank if including more devices, so you can move homey closer to device without always restarting it.

It seems this will not work for me.
I don’t have such option to simply turn on/off the thermostat. I can change the thermostat mode (Comfort, eco, etc) or set the target temperature but I can’t just turn it on/off.
So I could do flow that if sensor temperature changes and temperature is less than target temperature I can switch the comfort mode or set the target temperature but this still can be affected by the internal thermostat sensor.
Unless I set some stupid values to Eco and Comfort mode (Eco 5C, Comfort 40C), in that case switching the modes would do the job but it is not very elegant solution, is it? :slight_smile:
Any other suggestion?
Thank you
Peter

But writing that now, I remember I could just simply turn the thermostat heating on/off from fibaro app by clicking on the thermostat icon… Not sure why it is not possible in Homey :confused:

First of all, what is your thermostat model?
I have Heatit thermostat and its possible to turn it ON/OFF via mode selection (OFF/Comfort/Eco…).
So I have 3 options on my mind:
1st: as described above, but instead of ON/OFF the heater directly, you will chnge the mode to OFF/Comfort where Comfort temperature will be higher then target temperature of virtual thermostat.
2nd: replace thermostat with adequate smart relay (depends on the floor heating load) and controll it via this relay.
3rd: As you proposed, change target temperature based on virtual thermostat state (e.g. when virt thermostst is ON, value will be 26C when OFF, 18C).

My thermostats are Heatit z-trm2fx. I do have Off mode too. That would solve the “stop heating” problem.
But for start heating the comfort temperature would have to be higher than the target temperature.

Solution 2 would work but I’m bit worried if the floor would not overheat. So I’d like to keep the safe option of the thermostat switching the heating off in case the floor temperature is over 35C.

Anyway, I’m glad I’m starting to understand the logic and workflows in Homey :slight_smile:
Thank you for all your help and introduction to this new system

Peter

Ideal solution would be to send the measured temperature from external sensor to the thermostat and set it as thermostat air temperature. In that case the thermostat would turn heating on/off when needed.
But I presume this is not possible, is it?