Thermostat with OpenTherm and Zigbee?

Hardware
1

So this is actually two questions. One is a “am I thinking about this correctly?” kind of question and the other is actually about hardware if I am “thinking about it correctly”.

I currently have all my radiators with zigbee eTRVs, HA controls them directly via Z2MQTT. My water heater(tankless, gas) is a Vaillant with the cloud/wifi thermostat(Vaillant api integration for control, slow, unreliable, internet dependent. Integration itself has been good though, so thanks to that person for their work.). I have recently picked up the VR33 Opentherm module for the Vaillant boiler and plan on installing it once I have these questions figured out.

  1. My intention is to replace the current thermostat with a “smart” thermostat that supports zigbee and OpenTherm that is wired to the OpenTherm module(2 wire)so that HA can control the boiler via zigbee(via the thermostat), but also so that there can be a physical(albeit smart) thermostat on the wall(allowing the whole heating system to be manual if HA isn’t working or is removed…though with manually setting the eTRVs). In normal day to day operation I would want to continue to have HA controling the eTRVs as I do now. Again, assumption is that I am using automations to set per room eTRV temps and turning the boiler on as needed. So the first question is, is that an ok way of having it set up?(I think the below is a perfectly fine design, but I am open to being told it isn’t)
HA-->zigbee-->Thermostat
Thermostat-->OpenTherm/2-wire-->Boiler
HA-->zigbee-->eTRVs
  1. The actual thermostat…I have been searching online(google, amazon, aliexpress) with basically “thermostat opentherm zigbee” and have come up with lots of hits like this:
https://nl.aliexpress.com/item/1005004847622394.html?spm=a2g0o.productlist.0.0.707a6bc0fPHCTI&algo_pvid=dfcd4993-c628-45df-9c07-3fdd9ca58aea&aem_p4p_detail=202211260504346281445734384400003295580&algo_exp_id=dfcd4993-c628-45df-9c07-3fdd9ca58aea-29&pdp_ext_f=%7B%22sku_id%22%3A%2212000030727395011%22%7D&pdp_npi=2%40dis%21EUR%2181.29%2144.71%21%21%213.36%21%21%402101d68d16694678746618831e54a4%2112000030727395011%21sea&curPageLogUid=8RFlhfwbZd8c&ad_pvid=202211260504346281445734384400003295580_6&ad_pvid=202211260504346281445734384400003295580_6

Though while some of them will list OpenTherm in the title, I can never find it in the specs. Is OpenTherm either so ubiquitus with these thermostats that they don’t actually list it? or is it so rare that basically none of them actually support OpenTherm? Is OpenTherm just another name for an existing standard that all of these smart thermostats support, but in the case of european boiler makers they call it that? I am so confused.

Thanks for reading the long read and any light anyone can help shed on this subject.
Cheers,
John

3 Likes
2

My situation is similar to yours my boiler supports opentherm and now I’m using it with my nest gen3 thermostat but the integration is not reliable plus I have Aqara TRVs around my house and a good zigbee mesh. Did you find some zigbee + opentherm thermostats?

3

@j14s I’m curious to know if you got anywhere with this?

Without having GH directly control the boiler, I’m tempted to have HA do some of the work, and, if nothing else at least let me get the status and metrics out of the boiler.

I have about 90% of my heating wet underfloor based, and the remaining radiators, as well as a hot water cylinder.

I’d be keen to turn down the boiler by quite a margin when just the underfloor heating is calling for heat (which is the majority of the time), that should be fairly easy to setup without direct GH integration.

4

Good morning,
I am looking for the same as you. I have an OpenTherm compatible boiler. I would like to control it with Zigbee without the Cloud.
Did you find a solution? If so, I take your conclusions.

Cheers,
Pierre

5

Hi,
Im searching for this as well. In my home the rental company uses Salus wireless thermostats (RT310RF). I found this (link) on their website. An USB dongle that can communicatie with their products using zigbee. I have to dive deeper in this product, but it is a start. Does anybody has expierence with this?

salus-controls.eu/product-card/co10rf-zigbee-network-coordinator

EDIT:
This product can be used with the following
VS20BRF
RX10RF
The nice thing about the USB dongle is that it is used in offline mode (no internet cloud)

Cheers,
Iwan

6

Hooking on to this topic because I have the exact same plan: Zigbee TRVs controlled by HA with manual setpoint fallback, smart module to control the boiler via OpenTherm, the module should have a manual control of the boiler (preferably with a temperature sensor/thermostat) in case HA is not reachable.
I would prefer the OpenTherm module to communicate with HA via Zigbee, it is more reliable for me than Wifi. That is not so easy to find apparently, except for this one: Plugwise Anna - Slimme thermostaat Zigbee 230V/5A OpenTherm - SlimmeDingen.nl
Any alternatives? Basically I am looking for a Zigbee equivalent of this: OpenTherm Thermostat 2 - DIYLESS Electronics , preferably with a similar pricetag

3 Likes
7

Anyone have a working setup in the meantime? I’m also looking into this and thought a Bosch Smart Thermostat II would work, but it does not support OpenTherm (at least I can’t find it).