Is there a way to use an ESP to connect to Worcester Bosch Greenstar Boiler to capture internal temperatures, pressures, and error codes? I’m not talking about controlling the heat (on/off).
Thank you.
Not strictly ESPHome but there is another project which provides an interface between Home Assistant and the Worcester Bosch Greenstar Boilers. It requires a hardware board (which can be ordered online). I’ve previously had this setup with my boiler but decommissioned it when I had some work done on the heating system - I’m planning on reintroducing it again though. It does provide heating control (which I know you’re not interested in) as well as providing status information.
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Fantastic! Thank you.
Can I ask which model boiler you have please, and where you found the service port? 3.5mm?
I’ve got the Greenstar 37CDi Combi boiler. It doesn’t have a 3.5mm jack so I wired the interface board onto the EMS bus terminals.
I ended up decommissioning it when we had a megastor unvented cylinder put in as we had more primitive controls put in as we’re no longer using the water heating circuit. The hot water cylinder is now connected to the domestic heating circuit via a valve so we didn’t want the heating controls modulating the boiler based on house and weather temperature.
I realised I should have left it connected to allow me to monitor the system. It’d have helped me debug some “issues” I’ve had since and also check on the efficiency.
Also I could have probably come up with a cunning plan to allow Tado to modulate the boiler flow temperature when it’s only the radiators calling for heat and then overriding the flow temperature when the hot water cylinder is heating.
Now with the massive hike in energy prices I’m considering isolating the unvented cylinder and return back to Combi mode again. If only I had a way to determine the efficiency of each methods. 
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I have the same boiler but cannot figure out where the EMS bus is on it. I presume it in an internal connection somewhere?
Are you able to provide any further information, please?
Thank you!
You’re correct - the connection is on the heatronic board. The pages 28 & 29 of following manual are what you need.
https://www.worcester-bosch.co.uk/support/literature/download/6720613700
The EMS bus connections are labelled B & B on ST19. Do make sure this is the right manual for your boiler though as there are different manuals for different ages of boiler.
For my original setup it was easy as I could see where the FW100 weather compensating controller was wired in and just connect the interface board in parallel.
Here’s the link to the manual for my old controls:
https://www.worcester-bosch.co.uk/support/literature/download/6720617763
Page 17 figure 15 shows the bus connections on the Heatronic 3 controller.
I hope the above helps. I’ll probably be wiring my interface board and ESP32 up again in the next few weeks to get a better insight into how the system is performing in its current retrograde setup with the Megaflow.