missing wire

Hello everyone,

I hope someone can help me, the wiring on my Honeywell ST9400c programmer as from left to right. earth wire, next blue neutral wire, next brown live, next number 1 white, number 2 as no wires. number 3 black, and number 4 brown. The problem I have the Tado diagram has not shown where to connect the earth, the diagram also shows white to HW/HC, black to HW/NO and brown to CH/NO, The problem is the diagram shows number 2 (no wire) to go to CH/NC, so how do l connect CH/NC.

I have sent an email to the install team not sure when l will get a reply.

Stay safe


Best Answers

  • GrilledCheese2
    GrilledCheese2 ✭✭✭
    Answer ✓

    You can ignore the instruction to connect a wire to CH/NC. It’s not needed when there’s no wire on terminal 2. Assuming you have a wireless receiver the earth terminal is third from the right.

  • GrilledCheese2
    GrilledCheese2 ✭✭✭
    Answer ✓

    Just disconnecting the old receiver won’t make the CH work. Tado should have given you instructions for bridging the wiring inside and making any unused wires safe.

    Over the weekend you could power on the old wireless thermostat and set it to maximum temperature. Keep the Tado units powered on too and the Tado system should work. Your house won’t overheat as the Tado thermostat will limit the room temperature.


  • Hi again GrilledCheese2
    I thought I was sorted when l did the hot water test boiler fired up no problem however when I did the central heating test boiler did not fire up so l have hot water but no central heating. I checked the wiring again and all the wifi connections no problem even the central heating light comes on which I have set to come on at 4 o'clock looks like hot water bottle tonight. Just sent a email to tado to see what they come up with. Regards chauffeur55
  • I think you may have a problem with bridging your old thermostat.

    I’m assuming your old room thermostat was wired and you have now replaced it with a wireless room thermostat. Tado should have given you instructions to connect two wires together? This is very important as it completes the electrical circuit and allows the wireless receiver to take control of the central heating.

  • Thanks for the quick reply, no it's a wireless thermostat that I had
  • If your old thermostat was wireless it must of had a receiver unit. What you done with the old receiver?

  • It's near the boiler with a red light on so would l be correct if l disconnect it
  • Thanks again just but the batteries back in the old thermostat and it's working l will email tado to get wiring diagram to disconnect the old receiver we won't be fighting over the hot water bottle tonight. Thanks again
  • Thanks you, you are a star l will email tado to get wiring diagram for the Honeywell receiver