Wiring Tado Smart Thermostat to Worcester 28CDi

Discussion in 'Electricians' Talk' started by Wa10, Oct 21, 2017.

  1. Wa10

    Wa10 New Member

    Morning,

    I'm hoping somebody may be able to help me, as the Tado support line is closed and only open when I am in work. :(

    I've followed the instructions provided via the online guide, which advised me to connect to Ns, Ls and Lr on the boiler, and to N, L and 4 on the extension kit.

    The only confusion iabfhat he guide advised to remove a bridge wire, however none of the terminals on the boiler were bridged. It currently has a mechanical timeclock fitted to control the heating, and this is already wires into the same terminals.

    I've tried with the clock remaining wires in (as the guide seems to suggest, as it says the clock must be left in the on position) and also with it not connected at all, however the heating just remains on constantly with the clock wired, or constantly off without it.

    Signal from Tado stat and the app definitely getting through to the extension kit.

    The extension kit jumper is in position 2 as recommended.

    Any help greatly appreciated.

    Cheers,

    Marc
     
  2. Don't you have a room stat currently fitted? That's usually where new 'Smart' stats get wired to - and replaces.

    Replacing the timer is optional - you either by-pass it or else simply set it to 'ON' 24/7.
     
  3. MGW

    MGW Screwfix Select

    Thermostats can be generally connected in one of two ways, the old way was as Devil's Advocate says was to remove a link which is used for either fitting clock (programmer) or thermostat and this simply turns the boiler on/off and since the modern TRV gives better control turning the boiler up and down rather than on / off only really used set high in a cold room to turn off boiler on warm days. The other method needs the boiler to be wired to accept something like the OpenTherm and then the thermostat works the same as the TRV and turns boiler up and down rather than simply on/off.

    Some thermostats have anti hysteresis software built in, this normally means as it approaches set temperature it start to switch boiler off and on and as it reaches set temperature the off time gets longer and longer, the so called smart thermostat measures how long it takes to get from start temperature to set temperature and varies the on / off times as it learns how long it takes.

    But for a room thermostat to work better than the TRV it needs to use the TRV as part of the system, although the control panel of the EvoHome is called a thermostat it is not really that simple, it uses the info sent from each eTRV to work out when the boiler should run, and if the boiler has OpenTherm how much output is required.

    There are two problems, one getting info on the boiler, and two getting info on the thermostat. I have looked for info on the Tado and it seems lacking, I can't find any reference to OpenTherm so it would seem likely it is one of those thermostats that claim to do loads but in real terms can't. Nest does have OpenTherm although many nest users can't use this feature. Nest also uses IFTTT which means it can integrate with eTRV from other firms like Energenie. Although it will never equal EvoHome.

    So step one is find the boiler instructions, if the boiler can use OpenTherm take the thermostat back and get one which can use OpenTherm, if it can't use OpenTherm then Tado is likely as good as any other system, I will assume it has some way to integrate with the electronic valve heads of the TRV? It seems Tado is not one device but a range of devices so no simple answer.

    It does depend on house and boiler how well it will work, my own house is open plan and boiler is not condensate type so any thermostat with anti hysteresis software would do, mothers house has doors on every room and has condensate boiler so the eTRV's control the temperature.
     
  4. MGW

    MGW Screwfix Select

    Sorry boiler instructions note two links 2 and 3 for clock and 5 and 6 for thermostat seems it does not have OpenTherm and output is variable 10.5 kW to 27.5 kW so you should let the TRV and by pass valve control boiler so the hysteresis is as low as possible, thermostat is to turn boiler off on warm days not to control it, so you want a simple one, not one with anti hysteresis software built in as the TRV's do that.
     

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