Digital EMS Opentherm connection Worcester Bosch 42cdi
Hi
It's clear that it is possible to control Bosch Combi boilers based on users actual experience.
But can I ask if anyone done it with a Greenstar 42cdi?.
I will try tado support but that at moment is taking a long time to get a response
I asked WB. their response below.
I have a WIRED room thermostat with digital connections direct to boiler. Potential free contacts. Wired as per instructions from 6 year ago or so.
ME - Is it possible to control a 42cdi with a tado wired room thermostat using digital opentherm connections
BOSCH - Hi James, no none of our boilers have OpenTherm capabilities. All third party controls must be 230vAC or we have our own EMS controls that will do load compensation and weather compensation.
ME- Perhaps you are saying that just as a be safe option?
BOSCH- No it is definitely true. We manufacture our own controls which have better modulation of the boilers than opentherm controls have. I know it is a topic that is being looked at as we move into this more conscious world of economy settings etc. but at present it is not possible to do
ME - ok - is there an interface that allows a tado system to work with WB? I think there was one for the dutch market
BOSCH - No there is not a way of using OpenTherm controls with our boilers, only 230vAC (high voltage) third party controls are compatible. If the tado system can be used with 230vAC then it can be used.
Comments
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I have got to the stage where my Worcester Bosch Greenstar 8000 is being “controlled” by Tado Opentherm using the Nefit OT to EMS adaptor, but it does NOT modulate the flow temperature. That means it’s no better than a 240v relay control. I’m awaiting an EMS2 update from Tado (if it ever arrives) but in the meantime I’m adjusting flow temp manually (from my phone using an EMS wifi gateway device from bbqkees in NL).0
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My experience with Worcester Bosch com 42CDI so far.
TO NOTE
- WB say it's not possible. Clearly it is.
- tado tech help strongly advise getting an installer to do. But its not difficult...
Rewired my V2 wired thermostat from relay to digital. + and - terminals. either wire to either terminal.
In the boiler I disconnected the wires from the thermostat from terminal LR and Ls
Using a piece of insulated wire (with additional white insulation for identification)I bridged the two terminals LR and Ls where the relay wires from thermostat were installed before removal a few minutes earlier.
I then took the cable with the two wires that I had just disconnected from LR and Ls and attached to terminals on the right hand terminal block labeled B and B. The orientation is agnostic, ie you can wire either wire to either B terminal.
So now the thermostat downstairs is connected using the + and - terminals in the thermostat to the B and B terminals in the boiler. And terminals LR and Ls are bridged
On the thermostat I entered the installers menu and selected D17 as the config menu ID. I found that tado tech advice had done this already, so if you want you can do it yourself or get Tado to do it.
This is now working, and am monitoring to see if actually modulation the flow temperature.
some instructions re the installers menu. there is another document somewhere that has the table of all config menus for different boilers but I cant find it. Best check config with tado, who can remotely choose the correct confirmation for you too..
ps after turning power off to boiler you will get an error message flashing ups on boiler. Its most likely just the process of refilling the boiler syphon and stops flaring on and off after say 20 mins or so..
Tado installers app (useful) confirms above.
Some pics to help:
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The wired room thermostat with wires moved from relay to digital...
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That is an excellent write-up, Jamese8. Do you have any follow-up as to whether you were successfully modulating the boiler temperature (and thus, presumably, the gas flow)?
I don't know anything about the capabilities of the tado thermostats but my first reading of your write-up seems to suggest that you are trying to control an EMS bus boiler using an Opentherm bus thermostat without any intelligent interface in-between them. I'm a bit surprised you have got as far as you have.
I have just bought a 2nd hand Netfit OT-EMS adapter. I am going to try and interface my Schneider Wiser wireless thermostat and Wiser HubR to a WB 42cdi boiler. The HubR has both 'relay' and Opentherm connectors for connectiion to a boiler. I will fit the Netfit adapter between the HubR and the boiler. I can see from your photos how to make the connection into the boiler. I am not aware of anything else that I need to do on the boiler to cause it to shift over to using the EMS bus for control rather than the on/off relay. Are you?
This is a link of how to connect the HubR to an Opentherm compatible boiler.
https://schneider-electric.zendesk.com/hc/en-gb/articles/360014449877-How-to-connect-the-Communication-Module
Any advice will be gratefully received.
Regards1 -
Sorry to drag this thread up again... I just wondered how you got on with your Nefit adaptor? I have had one in my possession now for a few weeks, and was intending to try and use it with a Nest and my BW 42Cdi Classic, but given I can't find many positive outcomes of people who have used the adaptor, I haven't gone ahead with the Nest purchase yet, and was considering Tado instead. Either way, very interested to know how it turned out for you - Did the Nefit adaptor work?
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