Worcester Bosch Greenstar 8000 Life 40C


I've just had a Worcester Bosch Greenstar 8000 Life 40C installed but I've not had a timer or thermostat installed.

I've not bought it yet but I'm going to Tado to control the central heatining, initially with just the starter extension kits and, when cashflow allows, upgrade each of the rooms to have a Tado TRV and possibly accompanying thermostat.

But when we move I'd like to take all teh Tado kit with me to the next house.

So, for ease, I'd like to get my plumber to fit a traditional timer to control the heating, which I can then immediately replace with the Tado Extension kit.

Then when we move I can remove the Tado Extension kit and replace it with the traditional timer.

My question is, which is the best traditional timer to get so that there is zero wiring to change when I install the Tado Extension kit and then zero wiring to change when I put the tradtiional timer back in?

Thanks in advance


Best Answer


  • As additional information for Paul and to make this a little more generic for others I have been considering a similar situation.

    I plan to buy a Worcester Bosch system boiler with hot water tank, the model Paul has is a combi boiler.

    For the combi boiler with Tado you would wire it up externally using a wall plate either like the one pictured by Tado or using the one included with the Tado Extension kit. The wiring shown in the example picture is for controlling the boiler in standard old fashioned 'call for heat' mode using an S-Plan or Y-Plan wiring approach.

    See - https://ensupport.getconnected.honeywellhome.com/s/article/What-is-the-difference-between-an-S-plan-and-a-Y-plan?language=en_US

    However with modern boilers and with Tado it is possible to use an alternative more advanced method of controlling boilers using either OpenTherm or eBus protocols. This uses 'modulating' control. With the old fashioned 'call for heat' approach the thermostat 'calls for heat' at full power until the heat desired is reached and it then indicates to the boiler it is 'satisfied' and the boiler turns off. With modulated control as the thermostat detects the desired heat is being approached it tells the boiler to reduce its power.

    The difference is that with the old approach of running full power until 'satisfied' it will typically over shoot the desired temperature and then wait until it drops below before calling for heat again this results in constantly over shooting and constantly cooling below the desired temperature before firing up again. This unevenness is therefore less 'comfortable'. With modulated control this unevenness is dramatically reduced and this approach also has the benefits of reducing overall gas consumption and also I believe imposes less stress on the boiler.

    OpenTherm and eBus can also send diagnostic data from the boiler to Tado.

    As I mentioned the wiring shown is old style 'call for heat' wiring. OpenTherm and eBus use a digital interface and use two separate wires for this purpose. The Tado Extension plate has two additional connectors for this. I have not yet seen one but I would expect some standard plates also have these additional connectors however a lot of advanced controllers these days use non-standard plates e.g Worcester Bosch's own ones.

    For Paul I would agree the simplest option is to do the following

    1. Provide enough wires between the boiler and wall plate to support both traditional and eBus (which is what Worcestor Bosch uses on UK boiler models, they use OpenTherm on Dutch models)
    2. Ideally configure the boiler to use eBus not 'call for heat' as this as explained above is superior and supported by Tado
    3. Install the Tado ideally with the matching Tado Extension kit
    4. When wanting to remove Tado and revert to a cheaper alternative e.g. when moving out, remove the Tado and either leave the Tado wall plate in place and fit to it a 'call for heat' Drayton controller or also replace the wall plate with the Drayton one (Drayton use standard UK wall plates), it would clearly be a lot quicker and easier to leave the Tado wall plate in place but this would mean either sacrificing the Tado Extension kit or trying to get a replacement wall plate from them to re-use it at a new house
    5. Reconfigure the boiler to use 'call for heat' mode (I believe this may involve fitting/moving/removing a jumper), all the modulating controllers I have seen need Internet connectivity and an account to the matching company and if you are moving out this may not be practical - Drayon have their own Wiser range for example, a 'standard' traditional call for heat controller has no such requirements being a 'dumb' device

    Note: The Worcestor Bosch system boiler I am considering is a bit different. It also can use an external Thermostat in either 'call for heat' or eBus modes and both could be used and Worcester Bosch also do their own external 'smart' controller and thermostat. However for the model I am considering they also do a 'standard' controller which clips on to the front of the boiler itself and directly connects. This does not preclude the possibility of switching between the two but definitely would involve some internal adjustments to change between the two.