Adding smart boiler control

In my previous post I described replacing conventional thermostatic radiator valves (TRVs) with smart valves (sometimes called eTRVs).  The smart valves include both temperature set points and a schedule which allows me to operate shorter on times in rooms not used so much – such as the playroom heating turning off after my daughter’s bedtime.

My latest update is to link the valves to the boiler so that heat demand from a smart valve fires up the boiler, regardless of the settings of the older central timer and hall thermostat.  That would mean, for example, that if my wife want to watch a late film then commanding heat in the lounge would restart the boiler even if outside normal heating hours.

The effect of this change can be seen in the attached image which shows three days of valve position information for the two radiators in the lounge: two days where the boiler was enabled by the conventional timer and central thermostat, and the third day with smart boiler control.

For the first two days you can see the valve open wide for an extended period during some of which time the boiler won’t be pumping hot water as the hall is up to temperature.  However on the third day, with the link to the boiler, the valve closes very quickly from its initial position and then modulates to maintain the temperature since the boiler is running all the time when any valve is open.

The system is controlled by two rules through Apple Home:

  1. If any valve moves off closed (triggers)  then enable boiler.
  2. If any valve moves to closed (triggers), and all valves are closed (conditions), then disable boiler.

The picture shows the actual mechanism to turn the boiler on or off via the Elgato Eve Energy (which is a switchable mains outlet and energy meter) in the right side socket outlet.  I use the Eve Energy to operate a mains relay (in the black box) which in turn closes a contact between two terminals of the heating wiring box, which bypasses the heating timer and hall thermostat, sending a mains control signal to the dual port valve for the heating thus opening the valve thereby enabling the boiler through the existing controls.

The first evening’s operation showed two issues:

  1. Room temperature was reported as overshooting in some rooms, but not in one room with a newly installed valve. It may thus be that the older valves have self-tuned their controls and need to re-tune to the new more dynamic system characteristics.
  2. I needed to manually turn down the radiator in the hall which was getting too hot.  If that persists then I may need to add a TRV or smart valve to the hall.
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6 thoughts on “Adding smart boiler control

  1. Greening Me Post author

    And indeed we did add a standard TRV to the hall shortly afterwards to prevent it going over temperature.

    We may also add TRVs to the towel rails in the bathrooms for the same reason.

    1. nick-rackham

      Hi, any chance I could pick your brains on the automation config for setting up the Auto on and off for the Eve smart plug? also what do I need and where can I get it (I’ve 13 eve TRVs, 15 Eve door and window sensors and an Eve smart plug) my default radiator in the hall with no TRV is overriding the heating pump and I’d like to know where to get the mains relay and wiring diagram that I need to bypass the danfoss TS2, many thanks in advance, Nick

      1. Greening Me Post author

        I’m not familiar with the Danfoss TR2, but I can certainly lay out in more detail how the relay works in parallel with my own existing heating controls.

        I no longer use those prior heating controls for space heating but they are still present and could thus be used if the smart controls went down.

        I’ll write it as further blog post and link here as a comment like this doesn’t provide the same richness of format.

        1. nick-rackham

          That would be great thank you.

          I’ve managed to create the rules and scene to turn on the switch however struggling to create the rule to switch off if all valves off

          The TS2 is a two wire small Sensor that switches heating on and off located in the hall. Im assuming the switched relay will replace this

          Many thanks, Nick

          1. Greening Me Post author

            I use the Eve app to edit rules.

            The Eve app allows rules of the form: If {any trigger} and {all conditions} then set scene.

            Both trigger list and the conditions list includes all the values being closed – effectively if any valve closes and all other the valves are already closed then turn off the boiler.

  2. nick-rackham

    Rules now created with conditions etc. and all working as expected.

    I think the TS2 Sensor is a red herring. It’s a remote sensor not a thermostat so I’m going to disconnect it and then source a mains relay that will switch on power to the heating on feed. I think that should work.

    Many thanks,

    Nick

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