Boiler and raditors always on

Hi all, i've noticed there is a few posts about this but none seem to help my situation. I've installed the Tado wiresless reciever next to my boiler (ideal system 15), a wirelss thermostat which is in my hallway and just one radiator thermostat at the moment. The problem i have is that no matter what i change in the app, my boiler and radiators wont turn off. I've tried contacting Tado but have no response.

Attached are the photos of the wiring for the old Honeywell device and the Tado wireless reciever. I follwed the wireing instructions and everything appears the same


  • johnnyp78
    johnnyp78 ✭✭✭
    edited January 2023
    Sounds like a wiring issue. What do your two live wires connect to?

    You say you have a system boiler yet you don’t seem to have wired up the hot water. Is another programmer still connected?
  • i think i may be well out my depth here. We've only just moved in so bare with me sorry.

    The only honeywell that this has replaced doesn't have and capability to control the hot water so i've just wired this one the same way and according to the app. There is no other programmer installed controlling the hot water, it's just always hot.

    The on the Tado reciever the live wires go to L, bridge L and CH Com and goes to CH NO. I've attached a picture of the wiring behind

    Thanks for the insanely quick repsone

  • Your wiring is fine for a combi boiler, but if you’ve got a system boiler then you have a hot water tank somewhere. Are you sure it’s a system boiler and not a combi?
  • Sorry i do have a hot water tank located in our hallway, but i can't see any untis or programmers near it to chagne anything.

    The Boilers description is 'The logic system 15 is a condensing conventional boiler'

  • This is the boiler, probably no help though

  • I think you’re going to need to get a professional in. If you’ve got a hot water tank there’ll be a programmer for it somewhere.
  • Thought that might be the case, thank you for helping.

  • @dwilson223 do you have photographs or model numbers for the old devices in your hall and next to the boiler. Inadvertently disconnecting an Opentherm thermostat can cause a boiler to permanently turn on.

  • I do. The one next to the boiler was a Honeywell st9100c and the one in the hall was a thermostat Honeywell cm707

  • dwilson223
    edited January 2023

    This is the wiring that was in the two old units.

    Honewell.jpg is the Honeywell st9100c that was next to the boiler

  • dwilson223
    edited January 2023

    Also, this might be how it should be, but i noticed if the thermostat is set to say 18 in the app, but it's 22 and the boiler and radiators are still on, i used a voltage checker and noticed the CH NC is lit up but has no wiring going to it, only CH NO has a wire which only lights up if the temprature is set on the thermostat to higher then what it currently is

    Edit: I think i've just done this wrong. I've ran through the instructions and the are actually like the image attached, i haven't wired anything into CH NC becuase there are no other wires coming out the wall

    (the last one didn't have that)

  • I think I know what is going on. Do you have an outdoor sensor on the wall behind the boiler?

  • We are mid terraced but i can't see anything on the front or back of the house

  • I thought you might have a Weather Compensation device which is a small white box that is mounted on a wall away from sunlight. Anyway, I think you've misunderstood your boiler setup. The CM907 is a combined thermostat and programmer which controls your CH. The ST9100C is a single channel programmer that controls your HW on/off times. I'm guessing the instructions told you to connect the 2 wires in the CM907 together? This will be why your CH is permanently on.

    For now you should:

    1) Reinstate the CM907 to get control of the radiators.

    2) Change the wiring on Wireless Receiver. Move CH COM to HW COM and CH NO to HW NO. This will give you control of the hot water through the app.

    3) Order a wired thermostat from Tado.

    When you receive the new thermostat connect the two wires to COM & NO in the hall. You won't have a use for the Wireless Temperature Sensor. You may need some help from customer support to configure the Receiver to control the HW, but not control the CH. Make sure they know your CH and HW are controlled by two separate devices.

  • Yes that's what i've done with the old thermostat wires.

    That makes complete sense. I will get the ordered and let you know how it goes . Really appreciate the help

  • I hope I've got it right, but based on the existing devices I'm pretty sure that's how it is working.

    Just a thought on what to do with the temperature sensor. After you've installed the wired thermostat and you have checked that CH and HW are controlled properly by the App. You could group the temperature sensor to the new thermostat (not the receiver), and put the temperature sensor in another room. The temperature measurement in the hall thermostat will be disabled and it will just be a slave device controlled by the wireless sensor.

  • @GrilledCheese2 Just wanted to thank you for the help again and let you know the new wired thermostat came and i wired that, and the reciever as you said.

    Happy to say the CH and HW are now all working as expected and displaying/controllable in the app.

    Thanks again for the help, i can't thank you enough. We are expecting a baby any day now, so getting this all sorted is a massive stress gone.