Attempting to replace a Horstmann three channel controller (H37xl) with a Tado Extension Kit.

Opork

Having read forum entries, particularly from Deezell and Navdra, I’m still not sure if this is possible. Could anyone advise/comment on my situation.

I have underfloor heating downstairs and radiators upstairs. I also have a hot water storage tank upstairs. The timings associated with the firing of the boiler are managed by a three channel controller (Horstmann ChannelPlus H37xl).

I have installed tado smart thermostats (replacing my old Honeywell wired thermostats) in each room downstairs, set the 'downstairs' channel on my Horstmann controller to permanently on and this works well based on the schedules I have created in the tado app.

I have installed tado smart radiator thermostats upstairs on all the radiators. Again these work well with the schedules I have created in the tado app - HOWEVER - upon setting the 'upstairs' channel on my Horstmann controller to permanently on, in anticipation of the tado radiator thermostats managing the call for heating, the 'heating' actuator for the upstairs area immediately opens and starts the pump next to the boiler. This actuator remains open and the pump continues to circulate water from the boiler to the radiators irrespective of whether or not any of the tado radiator thermostats are calling for heat or not. While this 'theoretically' works, in that the radiators will only actually heat up according to the schedules I have created in the tado app, the heating pump remain permanently on. For example, during the night when I have set the tado radiator thermostats very low (13), the pump keeps on pumping all night.

It had been my intention to continue to control my hot water needs using the third channel on my Horstmann controller, however I have now also purchased a tado Extension Kit and would like to install this in the hope that I can configure it such that the heating pump only comes on when the radiators are actually calling for heat, while it also controls my hot water demands.

Tado have indicated they do not have instructions to replace a three channel controller with an Extension Kit (as the Extension Kit is effectively a smart two channel controller) and have suggested I contact a local electrician to change the wiring.

I am hoping that in replacing my existing three channel Horstmann controller with the tado Extension Kit, I will be able to effectively 'short circuit' my existing channel 1 (which is the downstairs underfloor heating), which should continue working as it does now with the hardwired tado smart thermostats controlling the underfloor heating. And then rewire the Channel 2 and Channel 3 of the existing Horstmann controller (which are upstairs radiators and hot water respectively) to be Channel 1 and Channel 2 on the back plate of the tado Extension Kit.

Logic suggests this should work – i.e. it should enable my downstairs underfloor heating to continue to be controlled by the hardwired tado smart thermostats, while allowing me to control my upstairs radiators, via the tado radiator thermostats and Channel 1 of the tado Extension Kit, (without the upstairs actuator and central heating pump being permanently on), and simultaneously have my hot water controlled by Channel 2 of the tado Extension Kit.

Any thoughts/comments appreciated.

Fergal82

Do Tado do a single channel receiver or whatever they call them (extension kit?)?

I’m not aware of any 3 channel receivers for smart stats so you usually need a 2channel receiver (ch hw) and an additional single channel receiver for the other heating zone.

Should be easy to wire but having never used Tado I have no idea how you set this up on the app

Opork

Fergal82 - thanks for your response.
Tado only do one type of Extension Kit and it is a two channel module. While Tado wouldn't provide instructions on how to implement the Extension Kit in my situation, they did imply it could be implemented but would require some rewiring - hence my suggestion above, and I guess I was wondering if anyone had either already successfully done this or alternatively attempted it and determined it wouldn't work.

Fergal82

You could link the heating zones together so they are no longer independent- is that your plan

Opork

I have a number of rooms downstairs, serviced by the underfloor heating. Each one has a hardwired smart room thermostat and I am controlling them independently, with heating coming on and off at different times (depending on usage). I also have a number of upstairs rooms, each with radiators and I have smart thermostats on each of these radiators. Some of these rooms have two radiators (and these are 'zoned' as one zone), but each room is, as with downstairs, independently controlled depending on usage. On the tado smart phone app I have an 'icon' for each room and have set up schedules for each room. My hope is to be able to have each room heat up independently as determined by these schedules I have set up and to be able to use the tado Extension Kit to allow this as well as managing my hot water temperature (which at present is switched on and off using the Horstmann three channel controller).  
So while I'm not exactly sure how I would link the heating zones together, it would also go against my objective in implementing the tado 'smart' control system - but thanks for the suggestion.

Fergal82

If Tado doesn’t do single channel then I’m not sure how you’d go about controlling both heating zones via its controller (other than linking them)

Is it a requirement for the underfoor to be controlled by Tado if it’s got its own stats and schedule setup anyway?

Opork

Sorry, but I probably haven't explained my situation very clearly.
Prior to installing any tado components, my downstairs underfloor heating had individual mechanical (Honeywell) thermostats in each room, allowing each room to have the temperature set for that room.
Upstairs all the rooms have radiators and each one had a mechanical thermostat (Danfoss I believe), again allowing each room to have an individual temperature set. In addition I have a hot water cylinder with a thermostat on the side of it . All three components are controlled by a Horstmann three channel controller, which allows me to set on/off times for each of the three elements (1 - underfloor, 2 - Radiators and 3 - Hot water). Each of the three has it's own actuator which when heat is being called by the combination of the relevant thermostat and the on/off timer in the Horstmann controller, activates to set off the boiler pump and fire the boiler. The underfloor heating has a secondary pump specifically dedicated to pumping water around the underfloor piping loops.

As I wanted greater control over the overall system I decided to implement a 'smart' solution and because I wanted to be able to control individual rooms independently (and due to the extra capability around geofencing and open window detection etc) I chose to implement tado as that smart solution.

Hence I arrived at the position as detailed in my original post above.  

Answering your questions above (in reverse order) - the smart thermostats I have installed, and the app I'm using to manage the schedules for the underfloor heating are all supplied by tado - so tado is controlling the underfloor heating - but not via the Extension Kit, which I haven't yet installed.

I don't quite understand your first comment above (If Tado doesn’t do single channel .....). Tado's "Extension Kit" is not a necessary component if you only want to manage temperature in a single zone or multi-zone environment. It's function is to allow you to manage room temperature AND hot water temperature simultaneously.  My issue is that using tado, I want to manage three things (in much the same way my Horstmann controller presently does) - my downstairs underfloor heating, with individual rooms being regulated by tado smart thermostats, my upstairs radiators, with individual rooms being regulated by tado smart radiator thermostats and my hot water supply, with on/off timings for this being regulated by the tado Extension Kit, which although not installed as yet, will replace my Horstmann three channel controller.
However, as I mentioned earlier, the tado Extension Kit is designed for two channels (not three) and so I am considering 'short circuiting' the wiring for my present 1st channel (my underfloor heating), effectively switching it permanently on (and letting the tado smart thermostats manage the on/off calls), while rewiring the other two channels (presently channels 2 & 3 - upstairs radiators and hot water respectively), to become channels 1 & 2 on the back plate, so that the tado Extension Kit can manage them.
Again, I was hoping someone may have already ventured here and might be able to confirm this should work, or alternatively advise me it is not possible.

Fergal82

I’m struggling to visualise a system that has a mechanical stat for each room with only one actuator but I don’t work with underfloor so that’s probably why.
Without seeing how your system is setup / wired then it’s hard to say how ‘shorting’ the underfloor will affect your system. Just make sure you make a note of what wire does what so you can easily put things back if you need to.

Technically though if you can set schedules in the Tado app for the underfloor then you don’t need the horstamnn in the loop

Opork

Fergal82, thanks for taking the time to respond. Much appreciated.