Tado Radiator Thermostats not calling for heat

5 Jan 2020
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United Kingdom

I have just replaced my Danfoss TP9000 programmer and TS2 sensor with a Tado smart thermostat and extension kit. Replacement was easy enough with the online help guru.

The smart thermostat replaced the overheat sensor in the hall and the extension kit is in with the boiler. All was working well with hot water and heating controlled by the smart thermostat.

I then decided to replace 8 of my current TRV's with Tado smart radiator valves and everything appeared to hook up and function ok. But I have noticed the smart radiator valves do not automatically or manually call for heat from the boiler, unless the smart thermostat in the hall is calling for heat at the same time. I thought it may be down to the radiator in the hallway still being on a normal rad valve and not a smart one. Thinking of replacing it for a cheap TRV so I can then replace the head with a smart one. Tado seem to think I have a firmware issue. Just wondered what the guys on here with Tado thought may be the issue.

Look forward to hearing your thoughts.
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TRVs don’t call for heat via the boiler, the room thermostat(s) control the call for heat at the boiler.
I have only fitted wired Tado thermostats, but according to reviews, I believe that the smart TRV's do control the boiler wirelessly via the extension kit, the same as the room thermostat does. Assuming that they are communicating with it OK of course.


It's possible that a wired room thermostat will still override them for systems that aren't fully fitted with smart TRV's [Tado would be able to confirm]. However, in a system where all of the radiators are fitted with a smart TRV's a separate room thermostat shouldn't be necessary, so the TRV's could then take over control of the boiler from it.
Stem is correct; the Tado system is functionally equivalent to Evohome or Drayton Wiser. There is no master thermostat. All of the radiator TRVs can call for heat creating (potentially) a system in which every room can be considered a separate heating zone.

The Tado app should show multiple rooms to which you assigned the individual TRVs when you enrolled them into the system. Is it possible that you have assigned all the TRVs to a single room?

Tado operates thus:
Room with one radiator TRV - the TRV monitors room temperature and controls the radiator. It can call for heat from the boiler independently.

Room with 2 or more radiators and TRVs - the user chooses one TRV to act as the room temperature sensor. All TRVs in that room are then slaved off that TRV. The room (strictly the master TRV in that room I guess) can call for heat independently.

Room with 1 or more TRVs and a smart thermostat - I think that out the box the smart thermostat is set to be the master with all TRVs in the room it occupies slaved off it (this can be overridden). It can call for heat and all TRVs in that room are slaved to it.

In multiroom installs where you are using the extension kit to control the boiler the only use for the smart room thermostat is as a control point and temperature sensor that you can locate it in the optimal location (we use smart thermostats in our biggest rooms, bedrooms are TRV only, bathrooms are off the tado system).
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Thanks Stem and Gary_Funwick. So it would appear that my smart TRV's are not communicating with the extension kit. Also, I get the comment Gary: 'Room with 1 or more TRVs and a smart thermostat - I think that out the box the smart thermostat is set to be the master with all TRVs in the room it occupies slaved off it (this can be overridden).'

If I now put a smart TRV in the hallway with the thermostat, should I name it as another zone or keep the same name as what I have given the smart thermostat? I suppose if I did that the TRV would slave off the thermostat and shut down the heating. I think I can go into device settings on the thermostat and not select heating and maybe the TRV's will then call the extension kit dire t for heating and just use the thermostat as the hot water on/off selector.

Read more: https://www.diynot.com/diy/threads/tado-radiator-thermostats-not-calling-for-heat.536501/#ixzz6AGaryXV1
Just wondering Gary, how can you override the thermostat being the master? I guess it must be in device settings?
From the smartphone app it is <settings> <rooms> <measuring device>.

If you have separate rooms set up with only TRVs in them you should be able to fire the boiler by raising the set point in any of them irrespective of whether the wall thermostat is master in its room (hall?).

If you added all TRVs in the same room as the wall thermostat which came with the startup kit then the wall thermostat is likely master.

To use the TRVs to full effect you need to create multiple rooms (I have eight, I think the system limit is ten).

On last thing, because the control is done in the cloud there is an appreciable delay. It's a minute or so, not consequential in use but very visible when testing. Also I've found that the set point needs to be 2 degrees or more above ambient to guarantee the boiler will fire when everything is up to temperature. Again in practice it just works but it can be frustrating when testing. Something to do with its TPI logic I suspect.

Tado's helpline is quite helpful and they can see your installation from their backend which helps with debugging.
Thanks Gary_Funwick, It appears there was a firmware issue with the extension kit which the tech guys have resolved. I too was thinking of leaving the bathrooms of Tado and on normal rad valves (not TRV’s). Is this your set up? Do you have any issues like that? Do they heat up when another rad on a smart rad valve calls for heat? So many questions sorry.
Our bathrooms only have towel rails and simple non-TRV valves. They are fine for the winter months as one or other part of the house is invariably calling for heat when you need towels drying. It would be a problem for summer except that they have electric elements also that we switch to in warm weather.

One thing to consider is the variation in heating demand if you create too granular a system. Potentially a single radiator in a small room can cause the boiler to fire. We chose to keep bathrooms off the system and also two small home offices. These have conventional TRVs on them. One is south facing and contains a few PCs so it is never below set point unless some other part of the house is calling for heat. The other is more problematic and I am considering reinstating Tado in that room.

Bedrooms (especially small ones) would face the same issue - firing the boiler for a small heating demand. However for us its not an issue as we keep the set point in Bedrooms relatively low. The radiators therefore only call for heat first thing in the morning.

It might not be a problem if you have a boiler with a high modulation ratio or have equally sized rooms. We have oil and unequally sized rooms. I fitted a low loss header as Tado was running the system very cool (flow temps 50-55 degrees, burning on a 20 minute cycle) when everything was up to set point. The very low return temps were below the boiler maker's spec without a LLH.

That's specific to our case but don't underestimate that having a very finely zoned system can create problems.

I will say though that the Tado system is extremely effective when in use and very controllable (I'm sure the same of Evohome and Wiser). Its largely set up now and forgotten about. I do wish they would introduce a range extender however (we are close to the limit of range for one TRV and the bridge).

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