Replacing Honeywell ST9400C with Tado

All sounds fine. You’ll probably put the Tado box near the tank and valves.

@Tonygrewal1 Hello Tony. We replaced the same setup in 2022, it's straightforward for competent DIYer. The Tado V3+ wireless receiver replaces the Honeywell ST9400C. In the Honeywell wireless receiver, you'll join the wires on A and B (call for heat) with a Wago connector from the starter kit.

• Hello @Tonygrewal1 Sorry, the post was deleted while I was editing remotely. Reposted …

• 1. When you start the install, Tado support should give you wiring instructions. The Tado wiring guides are also on the main Tado web site. Alternatively, the Tado Professional app has details. 
  
  On the ST9400C, IIRC it's a 1-1 wire move. L to L. N to N. CH NO (4) to CH NO. HW NO (3) to HW NO. Add two purple links: L to CH Com to HW Com. Obviously, do this with the power off.

• https://www.free-instruction-manuals.com/pdf/pa_458238.pdf
  

• 2. Carefully open the Honeywell thermostat receiver. IIRC, it's a clip-on front cover. There should be four wires: L + N to power the receiver; and A + B for the relay. Disconnect the wires on A and B and join them with a Wago connector from the starter kit. Obviously, do this with the power off.

• 3. The V3+ 'internet dongle' and Tado devices talk wirelessly using IEEE 802.15 and 6LowPan standards, not the usual 802.11 home wifi. 802.15 is low power IEEE standard for IOT devices, with a design specification range of circa 10 metres. 
  
  Most 3-bed semis are less likely to experience the V3+ range issues that some have seen in larger homes or thick stone construction. Here, a 4-bed 1960s home, we have one rad outside range in the conservatory. We kept the dumb TRV. 
  
  There are workarounds for range issues by using e.g. an ethernet cable, wifi dongle, or powerline adapter. Our rellie with a 3-storey 5-bed Edwardian Villa uses a cheap Tp/Link wifi extender with ethernet port.
  
  4. Offline scheduling.
  V3+ users can now request Offline Schedule

  Emcee

  2 Sept 2024

  Dear community, 

  We are happy to announce that, as part of our ongoing tiered rollout, the V3+ Offline Smart Schedule is being made available to interested tado° users via the community forum. 

  Due to compatibility considerations, this offer is only available to community members with V3+ heating starter kits or add-on devices (available since 2019).

  About Offline Schedule

  The Offline Schedule lets measuring devices store and execute scheduled heating in designated rooms, even when internet connection within said rooms is lost.

  Once activated, Offline Schedule can only take effect on V3+ measuring devices (visible in the tado° app under settings > Rooms & Devices > RoomName).
  
  V3+ measuring devices consist of: 

  • Smart Radiator Thermostats V3+ (device model VA02 and VA02E)
  • Smart Thermostats V3+ (device model RU02 and RU02B) 
  • Wireless Temperature Sensors V3+ (device model SU02 and SU02B)

  Measuring devices measure rooms’ temperature and coordinate the execution of  Smart Schedules with other tado° devices in the Home—as long as these can be reached in the event of downtime. 

  Homes without the above-listed V3+ devices should not request the activation of the V3+ offline Smart Schedule since it will have no impact on their devices.

  How can I request Offline Schedule?

  To request an activation for your tado° Home, please fill-out this form. Please use your account email (found in the tado° app under Settings > People) to sign-up.

  Community members who fill-out the form can expect the feature to be implemented during summer 2025. Community members will receive a confirmation email once Offline Schedule is activated for their Home.

  You can learn more about the offline schedule feature and how it displays on the tado° app by accessing this article.
  
  What happens if my Home goes offline during my holiday while set to Smart Schedule?
  
  Once the feature is implemented, your tado° devices will follow the Offline Schedule as soon as they go offline, whether you are in Home or in Away Mode. Offline Schedule therefore ensures your set-up continues to follow your Smart Schedule when disconnected.
  
  The above is true even when users are in Away Mode for days at a time (e.g. when users are on holiday). Please keep this in mind and make the necessary adjustments to your Smart Schedule before heading off.
  
  Why aren’t all tado° users with V3+ Homes automatically given access to Offline Schedule? 

  To ensure a satisfying experience and consistent device behaviour, tado° has already rolled-out Offline Schedule among select target groups. We have now decided to continue the roll-out among interested community members in order to gather feedback outside the above-mentioned groups. Once you gain access to the Offline Schedule, please tell us about your experience in the thread below. 

  Should you need help with your Offline Schedule, do not hesitate to contact tado° support. 

• Hope this helps.

• EDIT: Reposted.

Our rellie connects to their Virgin router with one like this: