Ideal Combi Logic+ Wired Thermostat OpenTherm Installation

Hi All. I have an Ideal Logic+ 35 combo boiler and I've just installed the Wired Smart Thermostat starter kit v3+. I specifically chose this as both the boiler and the smart thermostat both support Opentherm. I had got confirmation from Tado that this combination would work before starting.

Wow! It's been quite a journey but finally got there. 😀

Other threads on this site show that people have had great difficulty with the Logic-Combi/wired-thermostat combination and looks like quite a few have eventually given up and reverted to 240v relay control.

I just wanted to share my journey as it may help others. My first attempts led to the boiler either being constantly on or constantly off (as others had found with Ideal boilers). I had followed the professional install guide and set the smart thermostat to D01 and HWx which should be correct for the combo boiler. No joy and no obvious solution via this forum - so on to the internet... This is what I eventually found:

Learning point 1: Not all Logic+ boilers are the same. Ones manufactured before 2016 (mine is a 2015 model) are subtly different. I got this info from an Ideal youtube video which deals with how to install their own opentherm control system on a Logic+ combo boiler.

2m 25 sec into the video it starts the section on the model of boiler that I have and the main difference vs the more modern version is that there is no link installed on the 240v room stat connection. It also shows how to make the internal connection from the built-in plug on the front aperture wiring loom.

Learning point 2: There is a simple test to see that opentherm will work with the boiler configuration before final connection through to the smart controller. I found the following youtube video

Which is generic opentherm installation advice. The interesting thing here is at approx 3m 45s in from the start it tells you how to do a very simple test by joining the two opentherm low voltage wires together for approx 10 seconds and see if the boiler starts. You can do this from the wiring to the smart thermostat back plate. This was really helpful as it first exposed a dodgy connection (I had trapped the insulation in the boiler opentherm connector) and it did then confirmed that the boiler would respond to demand via opentherm.

So, I finally connected it up and started to test it.

Learning point 3: There is quite a delay between setting demand on the smart thermostat and this being sent through to the boiler (either via the app or direct from the stat). I was at the point of giving up after setting demand to 25C and nothing appeared to be happening when the boiler suddenly bust into life (must have been about 2-3 mins). Don't give up too quickly😉

Anyway, appears to be working now - I'll update if I find any other problems.


  • petem86
    edited December 2022
    Hi there,

    I had so much hope when I read this, about connecting the two plugs together, I didn't understand what it meant in the instructions, bit the video helped.

    However, when I went to do just that, I didn't have the plus that's in the videos. Any suggestions anybody?

    Ps how do we upload photos? It would explain what I mean, by what's missing
  • You can upload photos on the desktop version of the forum. I suspect you mean you have the uk version of the wireless receiver, which doesn’t have digital connections.
  • Thanks for the heads up, I have a logic boiler and will be fitting the tado kit soon. Good advise to start with.
  • Bump. My electrican had to revert to relay as he seems to think it is missing something. I've read a few forums which mention some sort of harness but I have no idea!

    We brought our new build in December 2023 with a Ideal Logik ESP1 35 so I'm assuming its a 'newer' version.

    Hoping I can get OT working with this forums advice.