Worcester bus connection

Hi, I bought a V3+ starter kit and some TRV valves to connect to my Worcester Greenstar 32cdi compact boiler.
I wanted to modulate the boiler and thought I could do this using the bus connections. But the wireless receiver doesn’t have bus connections? It has park, P1 and P2. Can I use those or do I need an extension instead of the wireless receiver?



  • Rob2
    Rob2 ✭✭✭

    "park" is just a set of dummy terminals used to hold unused wires so they don't have to instruct you to insulate them. there is no useful connection on those.

    There apparently are different versions of the wireless receiver and its predecessor the extension kit.

    I think the versions sold here in the Netherlands always have both modulation and on/off control, but versions sold in other countries could be different. Here, the on/off control is on terminals COM and NO (plus NC for some rare situations) and the modulation bus is labeled + and -

  • Thanks Rob2. I’ve bought an extension, which will hopefully allow me to modulate.
    I find it quite odd that the latest receiver in the UK doesn’t allow modulation.
    Has anyone else successfully set up a tado system to modulate a worchester boiler?
  • I've got a Worcester Bosch boiler and Tado. Like you, I want it to modulate. I already have the extension kit plus a thermostat.

    I've ordered some cable for the control connection. Most of the instructions show the extension kit being wired to the EMS terminals in the boiler and the Tado thermostat communicates wirelessly to the extension kit.

    I have a conventional boiler and it'll be interesting to see how it deals with heating the hot water.

  • Thanks Montage, let me know how you get on.
  • Pete
    Pete ✭✭

    Hi, I’ve got a Worcester Bosch 30cdi system boiler. I have it wired to a tado extension kit and it modulates the boiler perfectly. In warmer times the boiler flow temperature automatically reduces which improves the efficiency as the boiler will condense more.

    For hot water I could not find a way of the extension kit switching a zone valve for the hot water tank. So we fitted a Worcester integrated hot water valve inside the boiler. Plumbed the cylinder flow and return to the the boiler and fitted the Worcester temperature sensor in the tank, wired back to the boiler (also have a high limit stat in tank which shuts down boiler if tank overheats, part G safety requirement)

    Called Tado and they remotely adjusted the settings on my system to enable the Worcester ‘bus’ communication. Tado now controls hot water heat up too (only irritation is that I can’t see the tank temperature from the Tado app).

    Had to adjust the settings on the boiler to stop it heating the tank constantly (as the boiler seems to default to a combi boiler style set up, rather than tank).

    Hope that helps someone get the modulation and hot water working with Worcester boiler.

    let me know if anything doesn’t make sense or if you have any questions.

  • I'll update as soon as mine is wired in.

    I'd also like Tado to be able to 'read' the temperature of the hot water tank. I've added a couple of sensors (DS18B20) and a microcontroller to the boiler pipes and I can see flow and return temps. I'm thinking of adding another similar to the hot water tank.

  • Thanks everyone. I have similar issues with a 5 year old Vaillant 424+ eco plus tado and want to modulate at the lowest temp possible but once a day sterilise HW in my cylinder at 50 to 55 deg C but can't do both, runs too hot on rads.

    I looked at the wiring on my extension kit and its as follows left to right

    Neutral - black wire connected

    Live - red wire connected

    Terminal 1 - unused

    Terminal 2 - unused

    Terminal 3 - yellow wire connected

    Terminal 4 - red wire connected

    Is this arrangement how it should be to make it modulate ?

    Many thanks

  • Based on that photo, it can't modulate. The digital comms, ebus or whatever will do that and the terminals are empty.

    What you want it to do, I expect, is modulate for the demand for heating (only). Then turn up the demand when you enter the HW cycle to get the cylinder up to temps.

    Firstly, I don't know how it will behave (yet). Secondly, if the heat and HW schedules overlap, I can't see how to avoid hotter rads for the duration of the HW schedule. Moving them apart would deal with that.

  • I've had a reply from Tado, but they have got the impression I want to connect the Smart Thermostat directly to the boiler. This wouldn't work for my HW set-up, so I've replied.

    Meanwhile I've run the control cable from the extension kit to the WB boiler.

  • Just to update mine. Tado have said they’ll stop actuating the relays in digital bus mode. This kills it off for me, as I’d have to replicate that work in an external box as well as switch to OpenTherm and decode that. Bit more of a project than I want to take on at the minute.

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