A TRV which can bind directly to an external temperature sensor

Hardware
4

@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).

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