I just have no idea where to start! Ideal Logic Combi C30 and how to wire to Opentherm


Hi all! So before I start, I'm well aware that there are many many topics regarding the Ideal Combi C30 and how to wire them to Opentherm. However, I see there are quite a few versions of it and because of that, I have no idea where to start with my installation.

I'll say that I don't have any tado equipment yet, but this is the system that I'd like to install based on reviews. Ideally, I'd like to use the Wireless system as my current thermostat is wireless too. And yes, I think that means that I'd have to buy the EU version of the extension kit to have Opentherm working too.

So, I'll start with some photos of my current setup. The current thermostat controls the Central Heating only.

My Ideal Logic Combi C30 Boiler

Full view of motherboard

What looks like some Opentherm connections, including a cradle which appears to go into the blanked off faceplate area.

The wires inside the blanked off area

Switch controls and power supply from the current wireless receiver

The current wireless receiver and the fuse for that and the boiler

The connections behind the wireless thermostat

Sorry for bombarding you with pictures but this appears to be the best way to show you what I'm working with. If you need any more specific photos, please let me know.

So, what is the best way to wire this boiler up with an Opentherm connection? I think the Wireless EU version of the starter kit is the one I need (https://uk.installers-shop.tado.com/products/wireless-smart-thermostat-starter-kit-v3-eu-version). And all of the how-to's and manuals I've seen don't appear to be very clear.

I'm looking for a little step-by-step from those who have maybe worked with this particular boiler. And also, if you're aware of or can foresee any challenges that I'll have to overcome, that'd be helpful too.

Your help is hugely appreciated!



  • johnnyp78
    Get the eu wireless starter kit. Unwire your existing wireless receiver. Looks like the Opentherm harness is already installed on your system so you should be able to connect the Opentherm terminals without doing anything else. You’ll also need to power the wireless receiver from l and n.
  • Have the same boiler connected wirelessly but using weather compensation on mine with the black wireless kit from Screwfix, connect into the open therm on the right and I used the power from the supply at the boiler to power the receiver

  • johnnyp78
    @robti that doesn’t make any sense. The Tado wireless receiver on sale at screwfix doesn’t have any digital connections so you won’t be able to connect it to the Opentherm terminals.
  • No I was just saying how I wired mine using wc and tried to explain that he would just wire in the eu version into the ot on the right

  • Thanks for your reply @johnnyp78

    Would I be correct in saying that the brown and blue wires that are connected to the "ROOM STAT/TIMER" are going to the existing wireless thermostat terminals marked "3" and "4"? And can those just be disconnected and left completely?

    I'd also need to disconnect the power supply from the existing wireless thermostat terminals marked "L" and "N" and park them in the "L" and "N" terminals on the tado wireless thermostat? Also, where would I put the existing Earth wires that are currently screwed onto the existing faceplate?

    Then, how do I connect to the opentherm wires? I'm aware that there's no polarity, but the current wires are so far away. There's those loops in the faceplate area but how do I get those all the way to where my wireless thermostat will be mounted and which one is which? Do I need to buy some more cable and what type will I need?

    Sorry for all of the questions!

  • johnnyp78
    johnnyp78 ✭✭✭
    edited February 2023
    Parking means putting existing live wires out of circuit in a safe terminal. Don’t do this. You need to completely unwire the existing wireless receiver. You can’t use the existing faceplate on Tado’s wireless receiver, it’s an all in one unit so you’ll need to remove that too.

    Run l and n from the boiler to the Tado wireless receiver. Probably easier to use a separate wire for the Opentherm connection due to it being on the other side of the boiler. Any kind of bell wire will do or a spare power cord you have lying around. Or you could use the brown and blue wires you’ve disconnected from the relay circuit. There should be a ground terminal on the wireless receiver for the earth wire.
  • Hi @johnnyp78

    In that case, "parking" was probably the completely wrong terminology. Apologies!

    Seems fairly straightforward I think. I do believe that it could be a case of trial and error with the opentherm connection, but I don't think there's much I could do wrong as it's a low voltage connection (so long as I keep ALL live wires completely away from it!"

    Massively appreciate all of your help!

  • johnnyp78
    It was that simple on my ideal vogue so fingers crossed. It also helps to download the Tado pro app so you can set the Tado to use Opentherm if it doesn’t do it automatically.
  • Hi, I have an Ideal Logic Max C30 Combi - newly fitted in 2020

    It has an Ideal Weather Compensation kit is installed with an outside sensor (now disconnected)

    March 2022, I installed a Tado Uk Wireless Smart Thermostat starter kit V3+ (I now realise it is not OpenTherm compatible) November 2022, I installed 4 Smart Radiator Valves, with the intention to install more (I have 10 radiators in total) setting the STRVs to call for heat independently, and I removed the Tado wireless thermostat from the device list. This all worked very well so far this winter.

    Yesterday we set about installing the Add-on Wireless Receiver (EU Version) - for Combi boilers' purchased new from Tado, we obtained the detailed instructions for our boiler from Tado Support, we firstly carried out the detailed changes to the original wiring in the boiler.

    We then removed the existing wireless receiver previously fitted from starter kit V3+ and fitted the new EU version and wired that as detailed, removed the EU plug and wire and wired it to the original live connection, then wired the OpenTherm wires to the digital +/- and parked the remaining wires. All the above was carried out by our electrician and overseen by me.

    We switched everything on, the boiler fired up and started heating the rads (all STRVs were set to call for heat), then within a few minutes the boiler stopped heating, on checking my app I noticed the original receiver was listed as connected, so I deleted it from the devices and left the new receiver connected. nothing changed the boiler was running but no gas was being used, turning on the hot tap fired the boiler and produced plenty of hot water.

    We could not get any heat from the boiler, I had already downloaded the Tado Pro app and had set the boiler for D01 openTherm, I rebooted everything, router, the bridge, my phone several times in our effort to get it to work, and also checked through the wiring changes and connections - we just could not get any heat from the boiler.

    The Pro App shows that all devices are connected and up to date and the boiler details

    We had to give up as it was late afternoon, so the electrician changed some wiring so we could use the heating as an off/on system, and he is coming back tomorrow to have another go at sorting this problem out.

    So there is my story and for sure it is something simple, but what is it, has anyone here got any ideas that can help me please.

    Thanks Graham

  • johnnyp78
    I would contact tado support to make sure it’s configured correctly at their end. I’m assuming your electrician checked that your boiler’s Opentherm harness was connected to the pcb.
  • Thanks for the reply, I am not sure if he checked the harness connection, but he will in the morning, and when we reconnect everything tomorrow if it's not working I will contact Tado support, do you have any idea of their response time? as we will have to undo the changes so we can heat the property over the weekend.


    Ps.... I know you can't be sure how long it would take them to come back to me, 😊

  • johnnyp78
    No idea. I would contact them sooner rather than later.
  • I believe my problems are here:

    We had tried to get this sorted, in our situation:

    Image 1, has a captive grommet holding a loop wires inside the box - wires not shown in step A

    Image 2, we could not get the connector apart - maybe we should have given it more force

    Image 3 what should we be connecting together, what are connectors 1 and 2?

    We sort of came to the conclusion that this was already done, and after a lot of time trying to get it to work we ran out of time, but today we are hoping to resolve this issue.

    However, I would like some input please to perhaps guide us regarding the situation., these images are not from my boiler - they are from Tado's installation sheets. I don't have any images of the wires coming through in image 1, but my boiler set up is identical to MetalJames above images 1 through to 6, his shows the wires into the stat /timer box the same as ours is.

    I appreciate the help I'm offered, thanks

  • johnnyp78
    johnnyp78 ✭✭✭
    edited February 2023
    It’s telling you to connect the Opentherm harness to the pcb. Remove the timer link plug like it tells you. Follow the wires from the Opentherm terminal and make sure they’re connected to the connector behind the timer compartment. If your electrician isn’t sure how to do this I would get someone else in. Those instructions are about as clear as you’ll get.
  • OK so our understanding that you are saying.
    1. Remove the block with the looped wire from inside the timer housing
    2.Remove the block from the outside so it's free
    3. Connect the looped piece to the now free block (2 above)
    Which traces to the opentherm connection.
    We have pushed this together and the colour of the wires match. We have done this and it still works as reported earlier. Are we missing something
    Thank for your help
  • This is what we have

  • johnnyp78
    From what I can see you’ve connected the timer link plug to the Opentherm harness, rather than connecting it to the pcb.
  • johnnyp78
    I don’t know if this helps https://idealheating.com/uploads/documents/installation-servicing-opentherm-harness-kit.pdf
  • Johnnyp78

    Thanks for your help and the PDF link, no wonder we couldn't get this to work, we had no chance and it became obvious to us there was a component missing to achieve the result we had hoped for. So at the moment we have removed the EU receiver and fully refitted the original receiver for now.

    Regarding the pdf I already have the OpenTherm/weather comp block installed and with wire from the loom attached to the bottom of the block fitted at manufacture of the boiler, not fully understanding how this works I would normally think I could just insert my OpenTherm cables into the top left side of the block and into the Eu receiver ....... but apparently not.

    I can't see where the "missing" wires are going once attached to the Timer/stat loom. All this seemed so straight forward except at this point, everything was so easy and I am really surprised that we may have to detach the printed circuit board to proceed.

    I thank you for your help with this.


  • johnnyp78
    You shouldn’t have to. What component is missing? Maybe get someone familiar with ideal boilers to have a look, as far as I can see everything is there. You do run wiring from the Opentherm terminals on the boiler to the opentherm terminals on the wireless receiver so not sure what you mean.
  • ohnnyp78

    Sorry for the delay coming back to you, I attach a pic from a different pdf, but similar to the one you sent me and also the link to the pdf.

    The component that we don't have is shown in my pic below number 5 and the wires, if you look at my pic above which shows my loom it is different than one shown in the pdf which is dated 2016 (my boiler was installed 2020)

    MetalJames pics 3,4, and 5 at the start of this thread are identical to mine.

    My thinking is that MetalJames and my boiler are the same and both our Opentherm/weather comp connection blocks are pre installed and wired in at the bottom of the terminal block,. the our loom that goes to the timeclock/stat housing has a lot more wires than the pdf pic, the loop wires that are connected to the end of our loom are the same colours as those into the opentherm terminal block being purple and black/white (we traced them back to the terminal block) and I believe that the plug in loop wires form the full connection to the opentherm terminal, thus doing away with the additional connection 5 in the pic - and we should be able to fit our 2 wires into the top of the opentherm terminal block which then go to the EU receiver into the + - digital connection.

    Sadly I don't know anyone that is familiar with Ideal Boilers, all the forums I have been checking out only seem to refer to the method as shown in the 2016 pdf, hopefully someone might be able to offer more Details.

    MetalJames how have you got on with your installation?

    Link to PDF

  • johnnyp78
    If your boiler was installed in 2020 I would be very surprised if the opentherm harness wasn’t already connected. I think you need someone who knows about ideal boilers (like one of their engineers) to look at it.
  • It’s easy to say from my armchair, but this shouldn’t be too bad to sort. It has OT connections. Some boilers just need OT connected and they work. Some need the SL looped at the same time (in addition). I’d have thought the timer loops where there as a bypass as there is not timer unit fitted in the boiler.

  • Hi @MetalJames did you manage to resolve the issue with a straight forward fix, currently facing this same issue on the logic combo 35. Thank you
  • healy93
    I have this exact boiler. I recently replaced my V3+ wireless receiver with an old extension kit that I managed to acquire. To make it work, I had to reconnect the bridging wire to the 230v room stat connections. It appears to be modulating correctly now. Interestingly, I now also have hot water control in the app, but I'm not sure if it actually does anything since it's a combi boiler. Does anyone have experience with what the hot water control does?
  • pcone
    pcone ✭✭✭

    On my Opentherm connected Baxi 830 combi, the hot water control in the app does let me control the hot water temperature. Useful if I'm doing some tough washing up, and want the water a bit hotter than usual

  • healy93
    @pcone interesting, mine didn't seem to do anything so I've disabled it now!