Advice on my setup idea to make my heating/radiators smart

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1

Hi all,
I have a modulating boiler (De dietrich diematic) with 2 circuits. One for downstairs (floor heating) and a circuit for upstairs (conventional radiators).
The boiler has a serial modbus connection, and I am able to use Home assistant to set and read parameters to the boiler.
For downstairs (the floor heating), there is no issue : during winter it is always on. Nothing needed here.
The circuit for upstairs with the conventional radiators is where I want to make an improvement.
Up till now, there is a wireless proprietary thermostat in the bathroom upstairs. We can use it to activate the heating in the bathroom. When we activate it,
the circuit starts to flow/heat, and because the thermostat is in the bathroom, the bathroom is regulated to the required temperature.
(There is no valv on the bathroom radiator, so it is fully open)
This thermostat is wireless, so we could move it to another room.
When the thermostat in the bathroom i activated, the other rooms are heated as well, but the only regulation that they have is their classic radiator valves.

So what I want to do :

  • mount smart shelly radiator valves on all radiators upstairs .
  • Put the proprietary wireless thermostat in our cellar where it is always chilly (so that its temperature sensor always sees a cold temperature).
  • Make an automation in home assistant that whenever one of the shelly radiator valves is activated,
    I send a modbus command to the boiler and set a setpoint for the upper circuit for e.g. 30°C.
    This will start the heating circuit, and because the thermostat is in the cellar, it will continuously keep
    the heat flowing through the pipes.
  • So now the shelly TRV’s can do their work (regulate the rooms or the bahroom to their individual setpoint).
  • When all TRV’s are switched of (or turned down), I send a new command to the boiler to stop the heating of the upper circuit.

So in a nutshell, I would be using home assistant to turn on or turn off the boiler (via modbus), whenever one of the TRV’s is activated.

What do you think?
would the shelly TRV’s be good for this? At the moment I only have wifi, no zigbee, because the Home assistant server is in the cellar,
and with an USB adapter, it would not reach the 2nd floor.

2

You don’t want to turn it off when you are not home?

I used to have a TRV on each of the radiators but have removed them all.
They are noisy, the internal temperature sensor is inaccurate since it’s too close to the radiator, they eat batteries like nothing (because it’s hard work to manipulate the pin on the radiator).

Since I already had temperature sensors in the rooms it was an easy choice for me, thermal actuator with a smart plug.
Completely silent and works on mains.
The only issue is that it has a long delay between turning them on and actual water flowing, like 5-10 minutes.
But in the real world you basically don’t notice it.

3

Interesting!
Which actuators did you use?

4

I use a basic model.
There are plenty of variations most of them are just on/off.
I have found one version that can use a PWM signal to set the valve halfway.
And that is the big difference between the two. TRVs can be set to any position but the basic thermal actuators can only be on or off.

The ones I bought costed about $10, the better version with PWM control is about the same as a TRV, but you don’t get the internal temperature sensor (which honestly isn’t great anyways).

During the winter when the radiators are turned off when we are not home it takes about 3 hours to get the temperature up again.

If you have valves on your underfloor heating pipes in a central place then you can use a relay board to switch them all individually very cheaply.