@RV93 Given you have the same boiler as me and I have HW de-selected on the thermostat it is indeed most odd! Anyway, that's a very minor annoyance - you have a tile you don't need to touch. I love the way Tado modulates the boiler when connected to the eBus. My previous Vaillant was 20 years old and Tado just switched it on or off depending on the temperature of the room. To have that incremental control is perfect. Enjoy!
The following article should get you started. As you will see it is typically a 2 wire 24V circuit with digital signals overlaid on top. OpenTherm and the various proprietary eBus implementations use the same wiring and voltages but with different command sets.
@jelockwood thanks lot. I was expecting something much simpler, however this is somewhat similar to overcomplicated modbus.
The most troublesome part is that this only specifies a rather low level, and everyone seems to send proprietary information over it. Now I understand where the "reverse engineering" part comes from.
OpenTherm uses the same physical link and it is an 'open' standard, however all the eBus providers have made theirs proprietary. Tado say functionality-wise eBus is better than OpenTherm. (OpenTherm was originally developed by Honeywell.)
As far as I am aware Tado is the only commercial smart home product that has managed/bothered to reverse engineer eBus as used by Vaillant and Worcester Bosch. Nest, Netatmo, Drayton, etc. all only support OpenTherm. There are various OpenTherm boilers on the market, even here in the UK.
Ironically, in the Netherlands there is apparently a legal requirement that OpenTherm be used so Vaillant and Worcester Bosch include and use converter modules to translate their internal eBus to standard OpenTherm. It is in theory possible to buy these modules and fit them here in the UK however despite being genuine manufacturer parts this will invalidate a UK warranty if discovered.
An explanation for my confusion over the VR65/66. I had no idea what this was but on digging around n the internet I can see that it is a control box to integrate various aspects of a heating system. I do not have this box. My Tado extension is wired directly to my Vaillant ecoTEC Pro 28. The + & - connections on the boiler eBus connect to the + & - connections on the right (24v) side of the Tado extension backplate. The Tado thermostat is configured to use D07 (Vaillant eBus) and hot water is switched off. To fine-tune my heating needs I have thermostatic radiator valves fitted. Once set I have not needed to change the settings on these at all.
Two weeks on and my Tado is behaving impeccably. It modulates perfectly - a need for a small temperature increase is met by the boiler heating at a lower temperature to meet that need. At any time my home is at pretty much the exact temperature I asked for in the schedule.
If your needs are straightforward like mine Tado will work with the eBus on a new Vaillant boiler.
I have a Vaillant Eco Tec 831 plus which has a Vaillant VRC700 STILL connected. I read in an earlier post that there will be conflict between Tado getting weather data from the internet vs local data from the Vaillant VRC700. I would therefore like to disconnect the Vaillant VRC700.Presumably rather then disconnect boiler side i could just go outside and terminate the wires going into the Vaillant VRC700 sensor?
i have just posted this and wondered if anyone could help
I have just found this within the VR66 manual, does this mean it meets the VR65 functionality that has been raised in this thread
I've been trying to connect my Tado Extension Kit and smart thermostat to my 938 too. Below is what my boiler looked like when I opened it up:
I connected the + and - on the BUS terminals of the boiler to the corresponding terminals in the extension kit. However, when I perform any changes in the Tado app, nothing seems to happen. Do I need to change any of the jumpers present above?
The boiler was fitted in Summer 2020, how old is yours? Perhaps I'm affected by the VR66 mentioned in this thread.
Extension Kit is firmware 81.1. I have configured D07 in the installer menu on the thermostat. What do you mean by setting the boiler to always on? Do I have to set the heating to "on" within the built-in menu of the boiler?
On a related note, the hot water controls appear within my Tado app, but changing the hot water temperature on the app doesn't seem to change the displayed temperature on the boiler. I will check all my wiring again tomorrow.
Your extension kit firmware is fine. The boiler itself needs to be set to permanently on, bypassing any boiler timer controller, so that Tado can take over control of the schedule. My boiler has no controls fitted at all since my intention was to use Tado from the outset. I'm not talking about the boiler menus, just any fitted controllers. Do you have any other time controllers fitted to your boiler?
Maybe you should contact Tado support at this stage - my Vaillant worked with Tado straight away, but is a simpler ecoTEC Pro 28 with no hot water tank. I do know that my installer and I were waiting for around 5 minutes for the boiler to implement Tado's first call for heat. My installer hadn't installed a Tado system before and he couldn't believe that it actually worked with the Vaillant eBUS. Apparently neither Hive nor Nest are able to. He is a Vaillant Advance installer and had always been told that only Vaillant controllers were able to interface with a Vaillant eBUS.
Cross-referencing with other posts where there is the same circuit board it looks like your jumpers are correct, but you appear to have something connected to the 230v terminals on the right side of the board. Where does that cable go?
Just noticed this post regarding the 938.
Did you manage to get it sorted? The bridge is in the 24V RT which is correct, eBUS +&- to +&- on the extension is correct. Is the 230v supply straight to a socket or a fused connection, or is it going to some older controls?
The boiler screen options don't change when Tado is in use if this is what you mean. Obviously the boiler should fire though, are you not getting the boiler firing for central heating?
I'd like to provide another reference point:
tado thermostat is wired to eBus + and - terminals in the boiler as per instructions from page 11 to 19 (Wiring: Vaillant eBus).
My results as of today (23/6/21):
The software version page shows the tado thermostat recognised as the Vaillant VR81 remote control unit.
I switched from (1) to (2) this morning because I really like the modulating control by VRC 430. It keeps the target flow temperature low (30–45˚, we're in the South of England) and the radiators not too hot when the heating is on. As a result, the air feels less stuffy. I removed the VRC 430 yesterday and started with (1). It works but when I called for heat (set to max 25˚), the target flow temp at the boiler is set at 68˚ (if I remember correctly), making the radiators too hot to touch. With (2), the target flow temp is 54˚. It is still too high (for the 16˚ outdoor temp as reported by the Vaillant sensor), I think, but not as high as with (1).
I would love to hear advice on whether (1) or (2) is preferable. I have absolutely no idea how VRC 430 controls the boiler in tandem with the tado thermostat seen as a VR81 unit.
In any case, I hope the above will help someone thinking of getting the tado thermostat for their Vaillant boilers.