Tado & Worcester Bosch Greenstar 30 Cdi Classic System Boiler with internal Diverter Valve
Our Installation:
Worcester Bosch Greenstar 30 CDi Classic System boiler - Installed in 2013.
Control is by:
LP20RF Programmer& Receiver and Digistat+RF Room Thermostat.
Boiler has internal diverter valve that switches between HW and CH as required, controlled by the Programmer. Therefore no zone valves installed.
Currently all radiators have Tado V3 Smart Radiator Thermostats.
We control the heating using both the Digistat+RF Room Thermostat for 'On' and 'Off' and the Tado app to target which rooms require heat. Relying on boiler modulation when rooms have reached their selected temperature. Remote bypass valve is also installed to help offload the pump when all radiators are off.
Although this may seem a little odd, when we installed the Smart Radiator Thermostats two years ago, there was no information that I could find to link the Tado system to our particular installation.
Although this works quite well for us at the moment, obviously having Tado directly control boiler heat demand would be better.
Is this possible with our system?
Comments
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Hi DickFromMK
Did you get a resolution for this?
I would like install Tado with Worcester Bosch Greenstar 30 CDi Classic System and integral diverter valve too.
I was wondering whether a compromise might be to set the CH to always on and leave the HW on timer. The Tado set up could then just control the CH.0 -
Have spoken to a colleague, who's worked with the diverted valve. He said that there are two challeges.
If using a Tado system to handle central heating, two things have to be considered:
1. The heat sensor, not the heat limiter should be wired to handle the cylinder.
2. Tado must confirm that their system will allow the diverted to work, given that the faceplate controller will have to be unplugged.
Does that make sense? Don't have direct experience of this myself.0 -
It does make sense, but I wouldn't want to mess about with rewiring the HW electrics nor disabling the faceplate controller to get Tado to work.
Instead we know the following:
1) that the internal diverter valve prioritises HW over the CH
2) the CH is controlled by an external thermostat somewhere and connected at the ST10 terminals
Therefore if the external thermostat is replaced with a Tado wired thermostat, the heating on the boiler is just set to ON and the user just controls the HW setting from the faceplate controller wouldn't this be a good compromise?
We could just then set the HW timer on the faceplate to come say for 1/2 hour in the morning and 1/2 hour in the evening to heat the water in the cylinder. Obviously the boiler would not heat the CH during these times, but it is a minor downside.
Does that sound plausible to you or your colleague?
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Your installation guide is here:
Greenstar 30 CDi System Installation and Servicing Instructions | Worcester Bosch
According to the board's logic diagram, all the measurements and switching decisions are taken first on the digital side of the PCB. The decision to switch on the pump, and set it speed and pressure; the decision to set the throttle levels; these occur at the digital layer, then handed down to the dumb layer, where the ST10 connector gets involved.
Now if you fit the Tado wiring to the ST10 side, you will be controlling the boiler's logic from the dumb side of the circuit board (PCB). Therefore there should not be any collision between requests arriving on ST10 and the requests coming off divertor valve side which, drives the digital (E-BUS) side of the PCB - where the cylinder sensor is placed (ST15) and where E-BUS controls can be placed (ST19), if the menu is set correctly on the boiler.
However am a little lost. You stated that you are running an LP20RF Digitstat, which shouldnt be talking to the ST10.
- If the RF thermostat is in fact an LP20RF, it should be communicating through the boiler's controller, in E-BUS language, via the receiver.
- One could dismount the LP20RF node and engage the ST10 plug, removing the loop at the ST10.
- Looking more closely at the board's logic, you seem to be right - the HW side will have command priority over CH side.
However only Worcester Bosch will know what the implications will be. Strongly recommend you call their tech team and press on them the fact that you'd prefer to operate the Tado gear, decommissioning the LP20RF and keeping the divertor valve operational, worked by the cylinder sensor. Get them to give you the answer in writing. If they baulk at giving you an answer, write to their head of service and ask for a formal position.
May I ask, given you have a V3 series compatible with E-BUS - why are you aiming to wire this into ST10, not ST19 and operating your home fully in E-BUS mode?
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Noooo! I am not the same person as the original poster! I was tagging onto this post because I have the same boiler.
My thermostat is a wired Honeywell thermostat with NC NO COM connections. Therefore for me, it will simply be a case of swapping that thermostat for a Tado wired or Tado wireless receiver.
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In addition to this, I have underfloor heating. I plan to use a UH8 Heatmeiser wiring centre to eventually communicate with the wireless receiver and the underfloor actuators. Therefore it will be the wiring center that calls for heat whenever either the actuators or the wireless receiver needs it.
The wiring centre is 240V so therefore I can't use E-BUS anyhow.
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"Therefore it will be the wiring center that calls for heat whenever either the actuators or the wireless receiver needs it."
Sorry, I meant the Tado wired thermostats connected to the actuators via the wiring center rather than the actuators themselves…
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@stingwray . You have UFH wiring centre, controlled by wired tado stats that trigger the pump for the UFH, with the call for heat relayed by the wiring centre. That right?
This is a system boiler, presumably with the diverter valve controlled by a temp sensor at the cylinder, but your central heating is switched by the UH8 wiring centre, with the Tado stats behind it.
What precisely is your problem? And by the way answers to specifics, eg if your cylinder sensor is EMS BUS, it does make a difference.0 -
Yes that is right to your first and second paragraphs. Don't quite understand what you meant by "answers to specifics".
I found this post as I was initially trying to work out how I could get my Greenstar 30 CDi Classic System boiler with an integral diverter valve to work with Tado. I came across this post as I was trying to find out how to wire the HW on the wireless receiver when the diverter valve was internal.
However, I then realised that I could just continue to control the HW from the faceplate and allow the Tado to only control the CH because my current room thermostat is just using a switched live and I could just wire the Tado to replace that.
Sorry was just trying to be helpful, but I realise now that I haven't really been helpful at all because the original poster's has a LP20RF receiver faceplate together with his thermostat which uses E-BUS whereas I just have a DT20 with a relay CH thermostat. Mind you this has been working just fine for the last 10 years with the HW control on the DT20 and internal diverter. I guess he could always change the faceplate to do what I intend to do, but without any modulation from the thermostat😊. It sounds like he is just using his thermostat for "On/Off" anyway.
Anyhow I'm not an expert, but the fact that you don't think I have a problem is encouraging because it sounds like my set up will work. However if you can suggest any improvements to it - I'd be grateful.
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