Replacing 3 channels programmer - (2 zones) Rads, UFH and hot water

sebjou

I am not an electrician or plumber but I did manage to replace my 3 channels programmer (Horstmann H37xl series 2 channel plus programmer)

I have a S Plan system (can easily be identified if you have 2 pipes going to your valves). 

I have 3 valves for each of these

• Hot Water cylinder
• Radiators
• Underfloor heating

I have 2 thermostats one upstairs for the radiator and one downstairs for the underfloor heating

The Hot Water cylinder and the radiators are located upstairs. The underfloor heating is located downstairs

This is the Tado products I have purchased

• Wireless Smart Thermostat Starter Kit V3+ with Hot Water Control - https://uk.shop.tado.com/products/wireless-smart-thermostat-starter-kit-v3
• Add-on Smart Thermostat - https://shop.tado.com/en/products/smart-thermostat

Upstairs

I now have the “Wireless Smart Thermostat Starter Kit V3+ with Hot Water Control” set up to control the heat for the radiators and the hot water cylinder.

The programmer was replaced by the wireless receiver provided in the starter kit.

It was pretty straightforward to swap the old programmer with the wireless receiver. And re-wire the thermostat by following the instructions.

Wireless receiver (All terminal number are read from the left to the right)

• Programmer terminal 1 (green/yellow) to earth
• Programmer terminal 2 (blue) to N
• Programmer terminal 3 (brown) to L
• Programmer terminal 6 to CH NO
• Programmer terminal 8 to HW NO

Thermostat

I followed the instruction provided (I was lucky the colour of the wires were pretty standard - the colour might be different for you)

• Joined Switched Live (black) and Live (brown) 
• Terminated Neutral (blue) and Earth (yellow/green)

IMPORTANT: After fitting the wireless receiver, I was left with one spare wire. The one that was wired to terminal 4 on the old programmer which was connected to the underfloor heating thermostat.

Downstairs

I have used the “Add-on Smart Thermostat” for the Underfloor heating.

The challenge with this Tado setup was to figure out how to supply Live to the new thermostat. 

Live used to be provided by the wire connected to terminal 4 on the old programmer.

To supply Live to the new thermostat I connected this spare wire (the wire connected to terminal 4 on the old programmer) to a connector in the wiring centre that provided Live.

Thermostat

I followed the instruction provided

• Live (brown) to COM
• Switched Live (black) to NO
• Terminated Neutral (blue) and Earth (yellow/green)

Last thoughts

Prior to disconnecting anything I tested the terminals in the old programmer and thermostats for Live so I knew where Live was coming to the thermostats and the programmer when the different channels came on when I turned on the heating and called for hot water. 

When I looked for information on how to do this I could not find anything hence why I am sharing this. Because it is very straightforward.

This worked with my setup, it might also work for yours too.

Good luck

sebjou

I might have counted my chicken too early...

Today I just noticed that when I turn on the heating downstairs with the wired thermostat, the relay in the wireless receiver also turns on which also opens the valves for the heating upstairs. This does not happen when I turn on the heating upstairs with the downstair valves.

I am not sure how this is possible. I though the relay in the box was controlled by the wireless controller.

Could some help me understand here?

Seb

johnnyp78

I can’t help you with your specific problem, which sounds like it might be a zone controller config issue, but all Tado devices are controlled by the bridge. Have you checked all the devices are correctly set as zone controllers?

sebjou

Aaaah.

Thanks for mentioning this. I had no idea about this feature.

So in the app, after changing the ground floor heating zone option to 'no zone controller (independent)'. The wireless receiver relay for the central heating no longer turns on when I turn on the heating downstairs.

Thanks for the tip @johnnyp78

sebjou

Forgot to mention

It now works as expected.

rw95

Hi, I have a very similar set up (the only difference being that my ch 1+2 on the Horstmann are the other way around i.e my channel 1 on the Horstmann is house rads, whereas I think yours was UFH and my Ch 2 is UFH whereas yours was rads).

Can I ask why you connected the spare wire (the one that was connected to terminal 4 on the Horstmann)  to a connector in the wiring centre that provided Live rather than to Live in the Tado wireless reciever?

Many thanks

sebjou

I cannot remember which channel was set to what.

But I listed terminal mapping for the "Wireless Smart Thermostat Starter Kit V3+ with Hot Water Control". You can see programmer terminal 4 is not in use. That's because there is no where to put it in. That's why I had to purchase an "Add-on Smart Thermostat" to control the UFH.

Programmer terminal 1 (green/yellow) to earth
Programmer terminal 2 (blue) to N
Programmer terminal 3 (brown) to L
Programmer terminal 4 to ...........
Programmer terminal 6 to CH NO
Programmer terminal 8 to HW NO



The Horstmann programmer Terminal 4 was providing Live to my UFH thermostat.

When I removed the programmer
and replaced it with the "Wireless Smart Thermostat Starter Kit V3+ with Hot Water Control" for HW and CH I was left with no Live going to the "Add-on Smart Thermostat". Hence why I connected the spare wire that used to go to the Horstmann programmer Terminal 4 straight to Live.

Hope that make sense. Good luck.

rw95

I can confirm this approach all works as described above.

In my case I just attached the spare wire (the one that used to go to the Horstmann programmer terminal 4) to the Tado wireless receiver 'L' connection as per the image below:

Essentially you just need to wire it as per the installation instructions for an S plan system (don't forget the bridges!) and add the second zone controlled by the add smart thermostat (wired) to the L supply on the receiver.:

Its also important to set the heating zone option to 'no zone controller (independent)'

Have to say I'm pretty impressed with the Tado set up so far. My next step will be to fit the Smart TRVs.

Many thanks @sebjou - I wouldn't have attempted this if I hadn't seen your original post.