Heating Control, turn on boiler when any TRV requests heat (UK)

Configuration
1

I have 8 radiators, each with with Sonoff TRVZB’s connected and a Tado Smart Thermostat (V3+) to control the boiler (a Grant, oil burner)

In addition, each room also has a Sonoff SNZB-02 temperature sensor on the ceiling of each room. The bathroom has a SNZB-03 opening sensor attached to the window (which is open when the shower or bath is in use)

Finally, the living room has 2 radiators. Both with the TRVs attached (included in the total count of 8)

What I’m trying to do, is have the boiler come on, when any of the TRVs call for heat, and turn off the boiler when not.

A deceptively simple idea, but I’m failing to try and understand the execution, or indeed how to actually go about it.

Obvioulsy, if one TRV is satisfied, but another is not, then I want to ensure the boiler stays on until all TRVs have met their heat requirements.

I’d rather not hard-code the TRVs temperature, as someone in the house may want to turn them up or down.

Could anyone give me some pointers on how to achieve this?

Thanks

2

Create a group with the switches each TRV has.
Use the group to trigger the automation for the boiler

3

Can anyone elaborate a bit more on this? Like the OP I use SNZB-02 and TRVZB, I have Better Thermostat to link them.
‘Create a group with the switches’ seems simple enough except that the TRV does not expose any switch entities related to heat. The only switch entities are child lock and window open. Nor does Better Thermostat expose anything Groups can use.

The TRV has an MQTT property called running_state that contains heat or idle, can I create a switch from that?

Thanks

4

Yes or you could make a template with all the TRVs.

If trv1 == running or trv2 == running ... 
  True
Else
  False
Endif
5

Can you explain how to do that please?

6

See here:

How to configure my TRV’s into HA to switch on the central heater? - Configuration - Home Assistant Community