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Is there a scenario where the Boiler will fire with all TRV's closed


I'm thinking of switching from Nest to Tado, the reason being is that I end up with livingroom at temperature where the Nest stat is fitted and all the others colder because the boiler is turned off when the living room is up to temperature. The radiator in the living room being the one with the fixed lockshield valves.

so I'm thinking that I would fit Tado smart TRV's to all radiators including the living room. Fit a Tado Smart Thermostat in the Living Room, and then each room calls for the boiler when needed.

I'm reading because the living room will have a Smart TRV and Smart Thermostat, you can choose which one is the master for that room, so I would have to think a bit about which one I would choose.

So in this scenario which device in the living room should you select to be controller for that room?

And also, with a setup with eight Smart TRV's and the Smart Thermostat, is there a scenario here which I could find the boiler firing with all the TRV's closed but the Thermostat is calling for heat?

It's a combi boiler, no external bypass.



Best Answer

  • andreig1978andreig1978 ✭✭
    edited November 2019 Answer ✓

    Hi Mike,

    I would choose the SmartThermostat over the TRV as the master (measuring) device because being located away from the radiator it will give better temperature readings.

    Either way when the target temperature is reached, the measuring device will give the TRV a command to close the valve and if no other rooms require heating the boiler will also be turned off.

    So in short, NO the boiler should not fire when there is no consumer.




  • Hi,

    Thanks for that.

    that was the missing info I needed. I couldn't find anything saying that the Thermostat could be set to control one of the TRV's directly. I thought that the TRV's only followed their own setpoint.

    Do you know how the communications works. Is all this contained within the property, or does it rely on an external Tado server to work?

  • Hi,

    I'm not 100% sure but I think the tado servers are needed where smart schedule / geo-location are involved.

    On loss of connectivity, if I remember correctly, the system still works but it just stays on the latest known set-point - see https://community.tado.com/en-gb/discussion/comment/984#Comment_984

  • Thanks for that last bit of info.

    That's killed the sale for me. Relies too much on having an internet connection to Tado Servers for simple things like heating schedules. I need a heating system that carries on as normal in the event that the Broadband goes down.

  • Apparently if you use Apple Homekit, the tado devices do not depend on cloud access and are managed by homehit directly. Im not an apple user, so I know nothing about homekit. But I am experimenting with Home Assistant on a raspberry Pi, and HA does support Homekit devices:

    So it may be possible to manage tado "cloudless" from a local hub like a PC or raspberry Pi, running home assistant and intefacing via the homekit api. I will experiment with this this week as I have a spare bridge and TRV anyway.

  • MichaelMichael | Moderator


    tado° sends the needed heating signal to the boiler and when it does not have a heat request the valves will close. Some boilers will still pump a while after the latest heating request (tado° is not in control of this), in this case it could happen that to much pressure builds up. If this is the case it is needed to open a valve all the time (not ideal) or a bypass need to be installed.

  • Or Tado could turn off the boiler a minute or two BEFORE the TRVs close; or leave them open until further order (it wouldn’t matter if the boiler is off and it would save batteries and avoid trvs getting stuck in the summer)
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