Zigbee Thermostat - return temperature dropped

Dear all

Have not found this item discussed in previous post - pardon if I missed some.

I bought 4 SONOFF Zigbee Thermostatic Radiator Valve in January 24. They work fine using zigbeeto MQTT; however I noticed that my return temperetur of the water going back to the central heating facility dropped by 10 degrees (from around 30 to around 20). I suspect it is because the new vavles turn on and off and not somewhere in between.
I have made helpers to monitor on/off status but cannot get a good reading for %close. I have tried using the internal temperature reading as well as using better thermostats using a room sensor.

If anyone else is experincing simliar problems, or have another system that avoids this problem I would be glad to hear them. Thank you.

Below is a mini graph I made from the room temp sensors(white lines), the grey area is the vavle temperature sensors, and the steep ones are the on/off signals from the termostats.

Screenshot 2024-04-03 130903

Its probably the other way around.
Thermostat that make small adjustments will generally result in a lower return temperature, because the heat gets transferred to the room on a regular basis, where as on/off valves will typically open fully and then some of the heat will not be able to be transferred to the room in the time it takes to travel through the radiator.

Thanks for the reply. It was actually what I meant :wink: That the new vavles turn on/off where as the old analogs have in-between settings. Sorry for the bad explanation.

So what I was looking for was a way to make the new valves make smaller adjustments. I can get readings on steps needed to turn on off - but not what step the vavle is on presently.


The new valves will make small adjustments all the time. It is not on or off.
The lower return temperature is a result of better valve control on the new TRVs.

I discovered we are awaiting a firmware update to the TRV that will enable this feature - 1.1.4 : it is however halted due to bug concerns.

Thanks for the reply!