Homey Community Forum

PID thermostat


Let’s go for an other question !
I’m looking for a way to create a virtual PID thermostat (proportional-integral-derivative).
Is it possible or should i buy a real one to do the job ? And if i buy a real one, which one ? is it capable of handling multiple room ?


I would always go for a real one, no dependency on Homey but managed by Homey for Setpoints.
Honeywell evohome does the job here, but tado° also delivers a multiroom or zone system and talks with Homey.

Depends on more than these two questions, type of heating and does it use OpenTherm or …

I don’t know what algorithm the virtual thermostat app [APP] VThermo is using, but if you ask the developer he might be interested in implementing it. However, I doubt a virtual thermostat can control the actual heater well enough to have the kind of control you are seeking.

I second Dijkers comments and am a happy Tado user with multi zone control. Homey does additional logic for individual family members, real open window detection and more. One thing to note with Tado, if internet is down, you’re back to manual control, not even basic clock thermostat functionality left. That could be a deal breaker for some.

As far as I know the VTthermo app, Virtual thermostats and also actual thermostats are all more or less based on “hysteresis” control. Please proof me wrong :wink:

In other words the heating is on when the set temperature is higher than the measured and turned off when the temperature reaches the set temp+hysteresis. Actual thermostats have also some on/off timed switching (They say its PWM, but made with relay/contactor) when the off limit is close, lets say 1C away, so that the temperature doesn’t overshoot the set temperature.

It would be great to have PID controlled thermostat, virtual or real one. That way you could finetune the heating so that the overheating and underheating could be minimized. Of course the tuning is still quite long process to do, because you have to adapt to winter/summer, moist/dry and so on.

Of course you could do the PID with Better Logic calculation or Homey Script if you have the time an skills to make it, but it would be nice to have for example additional app for it to make it easier to use.

True, but as Dijker mentioned, you need something to control the heater itself. So what will be on the other side of the virtual thermostat? An Opentherm interface? And what is connected to that to send whatever fine grained commands? And why would Homey be able to do better than smart dedicated thermostats?

I think the question is too much thinking outside in - it all starts with what is producing the actual heat, and how is that controlled before you can look at how Homey interacts with it.

You can control most boilers (even ones that also support OpenTherm) with a simple relay that turns on/off.

Sure, but on/off modulation is a bit back to the stone ages for modern devices, and it does not seem that this is what @jeremypsl seems to be looking for.

I have a shelly 1pm to control the power of my radiators and a aeotec multisensor 6 for temperature, in every room.

Devices that only support on/off are more common than you think, especially outside NL. However, judging by his latest comment, I think he’s heating his home electrically (also fairly common in certain countries).

@jeremypsl can you explain your heating situation?

I have in every bedrooms (6) :

  • electrical radiator powered by a Shelly 1PM
  • Aeotec Multisensor 6