Installation on a Vaillant

Hi there,

Just got my Tado (wireless receiver kit) and so far not impressed (explanation below) but I'm wondering if it can be resolved. Slightly frustratingly it is difficult to find specific installation instructions before ordering and registering a device - so it was hard to know if my system was compatible. I took the plunge and figured I would buy it and see, and return if not. My system is a Vaillant Ecotec plus 831, with a Vaillant 392f thermostat and 392f RF receiver.

When I got it on, I put the above in to get instructions for the installation. This is where I hit a blocker. If I select 392f RF receiver, I simply get 'tado is not compatible'. Now why on earth can I not find this out before on Tado's website? Should be pretty simple given they have a database. But anyway, I try the boiler - and I have instructions for wiring it in, though they are beyond me.

Now my question is, if the 392f receiver is incompatible with the Tado wireless system, then what are my options? Do I need to get it wired into the boiler differently? Or is this a lost cause.


  • eezytiger
    eezytiger ✭✭
    edited November 2021

    @jp89 Disclaimer - I'm just a homeowner with no experience of or interest in heating systems prior to October when I bought Tado. I am not an expert, so don't assume what I say to be 100% gospel, but I'll try to help.

    I self installed a Tado Smart Wired Thermostat with my Vaillant Ecotec 831 Plus boiler. Previously there was a Drayton wired dumb timer/thermostat.

    The Tado app guided me perfectly in removing the old thermostat and reusing and connecting the two wires into my new Tado thermostat. It was a very simple process and the instructions were detailed and perfect.

    Maybe Tado does not understand the specific Vaillant model of thermostat that you have - not in the database as it were. But I imagine connection needs will be the same, once you've removed the old thermostat.

    In the simplest case there will be two wires. These will either be for mains relay switching (the thermostat simply closes a switch to activate the boiler) or for e-Bus control, which is a low voltage and smarter connection type. If your system had an external temperature sensor this will be redundant, so I think there are just two wires to consider.

    If you look here you might be able to find instructions which will help. Basically it doesn't matter what is/was there before. What matters is how to connect Tado to the boiler. Just be very sure to understand whether your boiler is wired for e-Bus or Relay. You do not want your voltages mixed up. And make sure the power is off before you go fiddling.

  • @eezytiger thanks. That's helpful. I'm not sure if Tado is just misunderstanding as it says I can use the boiler, but not replace the thermostat receiver.

    I took the front off the thermostat and it is indeed just two wires, but I'm not sure how to interpret this in terms of compatibility. Have attached a photo in case anyone can advise - note it does say 'BUS' on the wire terminals, so maybe it is eBus.

    • @jp89 the 392f is an EBUS controller which suggests your boiler is not using relay control. There are huge advantages to using EBUS to control the boiler, which will bring savings and more comfort, so don’t be tempted to switch to relay control. Tado claim that their EBUS solution can control any Vaillant combi boiler, so worth contacting their support team to get the wiring instructions. If it’s a system boiler then the question of compatibility is more complex.

  • @GrilledCheese2 if Tado have an EBus solution that can control any Vaillant combi boiler, then why would they simply say it is incompatible? Seems strange.

    Aware of the advantages of Ebus so I am questioning whether this is worth it. My home is only a 2 bed flat so the savings won't be as high as with houses...after all if I need to pay a contractor to install it you start to eat into (and probably lose) the benefits.

  • FWIW I started out with Relay operation, as per the original installation, swapped to e-Bus for a few weeks, but have returned to Relay mode again.

    This is because, with 9kWh minimum output, the boiler can not modulate down anywhere near enough to hold flow temperatures as low as, for example, the 33C that Tado often requested, with only one or two undersized rads open for business at any one time to drain the heat.

    The boiler, with water already between 27C and 31C would start heating for as little as 30 seconds before it hit the temperature target of 33C, at which point the gas would cut off, the pump would run on for five minutes, circulating no new heat, and would then enter anti-cycling mode for several minutes, especially at these low temperatures. The rooms were warm enough, but the boiler was often firing up without adding new heat to the radiators. It was stupid.

    On occasion, when a new radiator came online, Tado might call for full heat and the boiler would go right up to the set temperature limit, but far too often it was dithering around at this silly 33C mark, with radiators sized for dT50, not dT12.

    Now I'm back to Relay mode, with a target of 60C flow. Now the boiler has a burn time of several minutes before hitting temperature target and shutting down again. But now the rads are getting nice and hot and doing productive work. The boiler still cuts the gas with return below 55C, so it's still condensing and efficient.

  • @jp89 Do you have the EU or the UK variant of the wireless receiver. The UK version does not support EBUS, but the EU version does. This may explain why the app reports it as incompatible. The thermostat when wired directly will support EBUS always.

    Difficult to say whether EBUS is a significant benefit for you, but obviously a greater reward for those who use more gas.

  • eezytiger
    eezytiger ✭✭
    edited November 2021

    @jp89 You could always stick with the existing boiler controller and just fit Tado Smart TRVs. This is how I actually began my foray into the Tado ecosystem. Since my old TRVs were 33 years old and non functional this was a massive upgrade in energy/cost management and comfort. However, it was only a couple of days before I added the smart thermostat, adding the next major benefit that any room could command the boiler to come on at any time, rather than depending on the main thermostat to be requesting heat.

  • eezytiger
    eezytiger ✭✭
    edited November 2021

    @GrilledCheese2 At some point Vaillant changed the internal controller board in the 831, which brought an end to Tado e-Bus control of that boiler. Mine is a UK model, but with the old, compatible controller.

    It's something like VR-65 OK, VR-66 not OK, or something like that. I don't recall the exact reference numbers, but I think that's right.

    EDIT : Yes, numbers are correct. Here's a reference to the VR65 e-Bus controller becoming obsolete and replaced by VR66, apparently without e-Bus, or not explicitly mentioned. I got my information from another forum. No personal experience of whether all this is true.

  • The VR65 is not used for combi boilers, system boilers only. This is why I wrote earlier that Tado compatibility with system boilers is more complex.

  • OK, thanks. Maybe it is this discussion that confused me, where the OP asks about 831 and someone starts chiming in about VR65/66.

    But I thought I'd seen similar remarks on the DIYNOT forums too.

    Regardless of all that, I know I've had it working, which is strange when Tado support have flat out denied that it works. Go figure!