Opentherm with Ideal Logic 30 Boiler

Hi everyone, I’m hoping somebody here might be able to offer some insight on a technical question I discussed with Tado customer support today.

I’ve currently got a setup consisting of two smart room stats, numerous smart TRVs and an extension kit. The boiler is being enabled by on/off control from the extension kit. I wanted to know the benefits of using the opentherm connection instead so contact Tado support. They have informed me that despite my boiler having opentherm capabilities, I am unable to connect it to my extension kit in this way. To quote their response: “ I've just checked your boiler and unfortunately we can not control this boiler using Opentherm. We can only control it via simple relay (On/off). This used to be possible, but connection to this interface needs an extra harness, which is why this interface is disabled for our devices.”

Does anyone know anymore about this or why opentherm can’t be used on my specific boiler model?

Just as some background, I’m a building management systems engineer, and I understand the principles of weather compensation, etc (although I must admit I don’t know a lot about opentherm protocol!).


  • jelockwood
    jelockwood ✭✭✭
    edited February 2020


    I cannot say for certain what Tado's reason is but I can say that On/Off control aka 'Call for Heat' control uses different wiring to OpenTherm.

    OpenTherm is a digital interface and only needs two wires and also runs at a different voltage. Call for heat is 220v and uses switches aka relays to turn that connection off. Typically you have wires for power, for the heating pump, and the heating mid-position valve, along with wires from the room thermostat to indicate whether heat is required or not.

    It could be that Tado are implying that the cabling to your Boiler needs to be replaced, or cabling within the boiler to link to their OpenTherm system.

    A possibly related example is that some Vaillant boilers can be fitted with a timer/controller on the front of the boiler and wirelessly linked to a matching room thermostat. With this example Vaillant setup there is no external wiring at all and hence nothing to link the Tado to. Perhaps they are viewing your setup as being like that.

    Here are some links that might help you.

    The wiring loom apparently comes with the Weather Compensator kit.

    Note: You do not want to fit the Weather Compensator itself as it would conflict with Tado's own OpenTherm control of the boiler.

  • Did you ever get this working? I have replaced my Nest gen 2 with Tado specifically for Opentherm + smart TRV’s and I spent hours of trial and error with no success.

    So we weren’t with heating last night I just wired it up to the relay for the night but I can’t understand why opentherm just doesn’t seem to function. Surely the whole point of opentherm is that it uses a universal communication so it doesn’t matter what thermostats/boilers you have?

    Any help would be much appreciated! So far it feels like a bit of a let down and I expected the opposite
  • I should have noted that I too have an Ideal Logic Combi 35
  • I've set up Tado with an Ideal Logic Combi 35 using Opentherm.

    For my boiler (part 47-348-58) it needed a wiring harness which came with the weather compensation kit (part 204914). A two wire plug connects to the PCB for the weather compensation part and then the Opentherm plug connects to the harness.

    Once the Tado low voltage digital outputs were connected it was just a case of making sure Tado was in Opentherm mode (D01 -> HC01).

  • Appreciate your feedback NeonDusk! That’s exactly how I had mine set yet it fails to work properly. This is the harness I needed so wonder if our control boards differ?
  • NeonDusk
    edited October 2020

    Apologies if this is an obvious question but did you connect you connect the two Opentherm plugs together? I've labelled them in the picture below.

    The other thing I would suggest that if the cable to the Tado thermostat is long you could temporary move the Tado closer to the boiler and try a different shorter cable.

  • you don't need the harness, just put the wires into the choccy block and tighten. If you search for logic combi opentherm kit it shows a better diagram for pulling the spare socket out of the empty timer box and reattaching etc. Not difficult.


  • NeonDusk
    edited December 2020

    Some of the Idea Logic boilers do need a harness as they have nothing connected to the Opentherm port on the PCB. My Logic Combi 35 needed the harness below which comes with the weather compensation kit.

    And this is it connected using Opentherm

  • Hello, I have an ideal logic 30w and already use tado connected on/off just.
    @NeonDusk what benefits have you noticed with using this setup? I take it it uses tados weather compensation. I've noticed that the boiler is nearly too powerful for my house now as only half the rads are on at a time really. Does the ideal modulate to compensate for this? The rads are so noisy when only three or four are on at night. Wakes the wife up. Not me- I sleep through anything.
  • I need some help with my Ideal Logic 30 setup. I got the same answer from Tado that Opentherm mode is not supported but with the positive comments here I'm confident it can work.

    @MrB @Arki did you manage to get this working?

    @NeonDusk did you enable Opentherm yourself using the Smart Thermostat? I don't think I am able to do this myself using the Extention Kit.

  • You can switch it over to OpenTherm yourself.

    See the professional installer manual at for how you can set it to OpenThem (D01) instead of Relay (R01)

  • tadouser1000
    tadouser1000 ✭✭
    edited February 2021
    @NeonDusk the instructions show you how to enable with a Smart Thermostat but I've only got an Extension Kit with Smart TRVs. Was hoping you had a similar set up but it seems like you've got a Smart Thermostat which let's you enable Opentherm yourself

    Thanks for getting back to me so soon :)
  • I see, thought you had an extension kit with wireless thermostat.

    In your case I think it would need Tado support to switch it to OpenTherm.

  • So just to update, I got support to enable Opentherm for me so I've got it all working now. My Ideal Logic 30 did not require a harness so it's possible that newer models don't require a harness for Opentherm.

    Just to note, support told me if I select Ideal Logic + model this would trigger an Opentherm installation. I did not try this so cannot confirm that this would work.
  • Blootoon
    edited November 2021

    Hi folks

    Was looking to jump on this slightly old thread. I was very much considering the Tado for my Ideal Logic 30+ combi.

    It is currently using a factory fitted receiver box behind the front flap which is connected to the Opentherm connection in the boiler. This box is receiving signals from a wireless freestanding thermostat (PRT3).

    My question to anyone but possibly Neondusk or tadouser1000 who stated that they had managed to set up opentherm on a similar boiler.

    I need to know where in the new receiver the opentherm wires connect to as there does not appear to be that option in pictures/videos i have seen so far or do I need an extension kit as the pictures i see of that look to have low voltage connections?


  • @Blootoon you probably need one of the following that has the Opentherm connectors that allow you to connect your Tado system to your boiler:

    • Wireless or wired smart thermostat
    • Extension kit (which I think no longer come with Opentherm connectors now.. in the UK anyway)
  • Blootoon
    edited November 2021

    @tadouser1000 , thanks for the quick reply.

    From other research, i did find that the opentherm extension isn't available in the UK anymore. Incredible, as they could have the whole market covered as neither Hive or Nest can offer both opentherm and Smart TRV's!

    I didnt want to have the thermostat wired as it would mean running wires which is a hassle.

    You mentioned the wireless smart thermostat though. How do I connect that with opentherm capability if the receiver doesnt have the necessary contacts inside?

    Also, do you know the part number (EK01 etc) of the extension kit that you currently use, in the event I can source one on Ebay or somewhere

    Thanks again

  • I have an Ideal+ c30 boiler and I'm also in the process of getting my central heating onto Tado - just trying to get an electrician to do the installation.

    I have UFH which is controlled by a wired thermostat and the radiators in the house are controlled by a sensor in the passage whose receiver is placed besides the Ideal boiler.

    I would be needing two wired SMART thermostats + 1 wireless sensors + Smart TRVs around my radiators (except for one).

    @Blootoon, do post an update on how things have gone for you and I will likewise post mine.

    Thanks to the others who have posted on this thread. Information has been valuable.

  • Blootoon
    edited November 2021

    @sednem I will let you know if I ever get to that stage.

    I went on to support today to be told that I could only set up as relay and not opentherm even with the extension kit, but it seems that @NeonDusk and @tadouser1000 managed to get something hooked up. If I get the extension kit model number they used, I will try and source one from somewhere like ebay.

  • NeonDusk
    edited November 2021

    @Blootoon If you have an extension kit or the Smart Thermostat with the Opentherm terminals I see no reason why it wouldn't work (once it's been set to Opentherm mode.

    I'm not using the extension kit, I have a Smart Thermostat connected using the OT connections to the boiler. I then have multiple Smart Radiator Thermostats and some other Smart Thermostat acting as wireless temperature sensors.

    Edit: I installed the wired Smart Thermostat right next to boiler so it needed just a short new cable (no power or any other connections). The other Smart Thermostats / Wireless Temperature sensors are then placed where I want them and they don't need any wiring.

  • Blootoon
    edited November 2021
    @NeonDusk Thanks for the reply. I just wanted to know which of the available extension kit numbers support opentherm as there are a number on ebay, but it's not clear from the listings. If they are all the same, I'll just go for the cheapest one.

    My boiler is in the garage, therefore wouldn't it always be looking for heat as it's always cold.

    With the additional sensors you have, are you just controlling the heat from the app?

  • NeonDusk
    edited November 2021

    As far as I can work out it's only the UK version of the Wireless Receiver that doesn't have the Opentherm terminals. I believe all extensions kits (which don't have physical buttons) do have them.

    I have the Smart Thermostat that's wired to the boiler in it's own Tado room with the temperature set to minimum so it never calls for heat.

    All the other rooms have their Zone controller set to the wired Smart Thermostat so that when they call for heat the boiler will come on.

    Mostly leave things on the schedule I have. If I do want a room hotter or colder and I've got my phone handy I can change it there or just adjust the desired temperate on the room's radiator Smart Thermostat / Wireless Thermostat.

  • @Blootoon this is the extension kit I have which is now discontinued:

    Tado support also initially told me that my Ideal Logic C30 wasn't compatible with Opentherm. I think they say this because some of the Logic models require a harness mentioned above to use Opentherm however my boiler didn't need this

  • I think the wireless smart thermostat (boiler connector bit) has changed since I last looked so it may not have the OT connectors but I may be wrong

  • I may have managed to source one with the opentherm connectors. I do not need the harness either as my boiler has both plugs to connect to the pcb. Waiting for confirmation before I buy the rest of the kit.
  • Great! @Blootoon I have the wiring instructions if you need them?

  • @tadouser1000 Hopefully if it's the correct kit, the instructions will be with it, but I'll let you know if I'm struggling. Thanks
  • Should be straight forward for you as you're replacing your current thermostat.. but just in case Tado do provide boiler specific instructions during the initiation process in the app or just shout if you need the PDF version and I can post it

  • Blootoon
    edited November 2021

    @tadouser1000 @NeonDusk I have managed to source an unopened extension kit on Ebay at, what I think, is a decent price. I also ordered the V3+ starter kit from Costco. It comes with the wireless receiver which I dont need, but I couldnt see a deal any cheaper than theirs at £99.95.

    My question is probably more to tadouser1000 as he has the extension kit fitted.

    I know to connect the two Opentherm connections on the kit to the Opentherm connections on the boiler.

    Do I need to power the extension kit from the 230v supply on the boiler too or can I just power it from the fused spur.

    Should hopefully have everything in my hands by this time next week and the fun begins.😉

  • Yes that's not a bad price from Costco.

    You can connect via spur or using the boilers 230v connectors. I can't remember if there is a power switch on the extension kit so if you do wire using spur just make sure you have a way of power cycling in case you need to restart it.

    Also remember not to confuse 230v with the 12v OT connections! They're at opposite ends inside the boiler so it should be easy not to make that mistake.