A TRV which can bind directly to an external temperature sensor

Hi, does anyone know of a TRV that can be directly bound to an external temperature sensor?

I currently use Philips Hue switches, which I can bind directly to Hue lamps. This is great because the devices remain operational even when ZHA is down, and it allows for a very simple configuration.

Recently, I purchased Sonoff TRVZB radiator thermostats. While they integrate seamlessly into ZHA and generally work well, I’ve noticed that their internal sensors are not accurate. Setting them to 20°C results in room temperatures of around 17°C.

I attempted to bind one of the thermostats to an Aqara WSDCGQ11LM temperature sensor without success. None of the devices show up in the list of bindable devices.

Considering these issues, I’m contemplating returning the TRVs and searching for ones that allow for direct binding. If you know one I would be very glad to hear!

I personally use the Shelly TRV. This offers an endpoint to overwrite the internally measured temperature, for example via HA automation or NodeRed.

If you want it to go through HA then look at the integration Better Thermostat.

I use Homematic IP.
It is its own system, so you need to buy their devices if you want them to work together independently, but they are also integrated nicely into HA.
Homematic IP devices can talk together directly, so a thermostat can have belong to a group or be single and a wall thermometer can then be connected to that thermostat or group, and you can also add their door/window sensors to those groups.
Homematic might not be available everywhere,but where it is it is usually one of the cheaper solutions and it can be integrated into HA with a cheap USB stick that makes it local only.

@elcajon Thanks for the info. This is interesting, but I’d like to stay with zigbee for this.

@WallyR I have looked into Better Thermostat, but it adds a lot of overhead to the setup. Same for the Homematic system.

Best case scenario would be a thermostat which allows direct binding via zigbee to an external sensor and automatically reads the temperatures from there, with no further configuration needed. It would still work if the server/coordinator goes down. I’m trying to create a very robust system, more on this in this thread.

I searched for a while and it seems that there is no zigbee TRV which allows that as of Nov 2023.

I think the closest I can get is with the Aqara E1 Thermostat.

It has a built in functionality for an external sensor, which it exposes via zigbee. From the docs:

Sensor (enum)

Select temperature sensor to use. Value can be found in the published state on the sensor property. To read (/get) the value publish a message to topic zigbee2mqtt/FRIENDLY_NAME/get with payload {"sensor": ""}. To write (/set) a value publish a message to topic zigbee2mqtt/FRIENDLY_NAME/set with payload {"sensor": NEW_VALUE}. The possible values are: internal, external

So in theory all you need is a sensor periodically send its readings to this endpoint. But I doubt that it will ever be possible to bind an external sensor to this TRV, as it seems that this is no standard protocol.
I find this TRV still to be the best option, because it allows for a very simple configuration in HA on the server side, while all the work is still done within the TRV on the device side. And if the server goes down it still works with its internal sensor. Even without direct binding I still consider this simple and robust.

Here is some info on how to utilize the external sensor for this TRV: Aqara TRV external temp via zigbee

Unfortunately there seems to be no ZHA support for this yet, but there is a request for it already on github: [Device Support Request] aqara Smart Radiator Thermostat E1, external sensor

I don’t get why there are hundreds of Zigbee light switches and lamps from different manufacturers which play nicely together out of the box with direct binding, but not a single TRV+temp-sensor combination… same for TRV+window-sensors btw… No love for us TRV people. (sorry for the rant).

I just found out that the Danfos Ally TRV also allows to use an external sensor, similar to the Aqara E1, but it also doesn’t allow direct binding. Here is a nice discussion about this exact topic on github: TRV Danfoss ally #4504

Your Aqara seems to be using MQTT, so you need to run a broker service somewhere.
And I have set up a few Ally TRVs and I can not recommend them for an integrated system.
They are ok in their own ecosystem.

And yes Homematic adds a bit of overhead, since you need to run a CCU, which is a service that can be run as an addon in HA and you need an USB stick, but that is also the case with ZigBee, Matter, Z-Wave and so on.
It is however one of the only systems I know that can run independently when the CCU is down.

Bump for the topic!
I am also interested in making Sonoff thermostat TRVZB work with external temperature sensor. Ideally based on HA Zigbee2MQTT, but other options are worth mentioning too.
What gets me to the idea that it should be possible is a print on the packing box mentioning integrations with external temperature and window sensors. So it should be possible or if not right now - at least they have plans to implement it later.

Hi @feluxe!
Can you please explain what list of bindable devices did you refer in the first message? Where did you find it? My HA Zigbee2MQTT integration doesn’t offer any binding possibilities.

So you got a solution for sync with external sensor?

I used to use blueprint to sync local temperature calibration with my old thermostat.

The problem is that the older thermostat can calibrate 0,5* nad the Sonoff can operate 0,2*. Can someone look at this script and adjust it?

I think it should work with this TRV

Fibaro Heat Controller, it comes with an external Bluetooth temperature sensor. I am using the Z-Wave version. But there is also a HomeKit version avaialble.

Hi, does anyone know of a TRV that can be directly bound to an external temperature sensor?

Bump for the topic!.
The case is typical and should be easy, but it doesn’t work. I have:
1)TRV602 Zigbee radiator thermostat,
2) Multimode Zigbee Gateway, and
3) External Zigbee temperature sensor.
I combine everything into scenes in the Tuya app, but TRV602 works according to the plan specified in the Tuya app, completely IGNORING the activated scenes based on the external temperature sensor, also being made in Tuya app.
I checked the scenes many times and in my opinion they were done correctly, e.g.:

Please help.

Eurotronic Spirit Z-Wave should be able to do that according to its documentation. I’ve tried to do this several years ago with two different temperature sensors but couldn’t get it to work. I haven’t tried the Eurotronic temperature sensor though, might be worth a shot.