How to read the Vaillant eBus

[OpenMike]

I have a Vaillant EcoTec Plus boiler. I don't want to control it but I'd like to be able to read the values of flow and return temperature so I can plot them on a graph.

I've searched the internet and it appears that this can be done with an Arduino, but most of the posts on the subject are in German which I don't speak.

Does anyone here have any relevant experience please?

Mike

[jvallis]

Ebus isn't an open standard, but there is a linux daemon called ebusd that can read the data, Vaillant's ebus implementation is constantly changing with their products and isn't widely known.

However, there is a solution but you'll need 2 devices:

Vaillant make a device called the VR33, which isn't available in the UK (and will invalidate your warranty if they found out), but can be purchased from Holland via https://wifithermostaten.nl/vaillant...dule-vr33.html. This will bridge ebus to OpenTherm.

With OpenTherm, you can then use an OpenTherm Gateway (aka OTGW: http://otgw.tclcode.com/), which is a not very useful serial interface, but thankfully Cyril has made a module for an OrangePi which means you can have it in a far more accessible computer/wifi interface: https://www.domoticaforum.eu/viewtopic.php?t=11816

[OpenMike]

Thank you, that's very helpful.

There are some very clever people out there

My boiler is 9 years old so no worries about the warranty ...

[OpenMike]

After some further research it appears that Vaillant used to offer their own solution:

https://www.mytub.co.uk/vaillant-vrd...product-107928

The hardware is no longer available but the software can be downloaded from some (non-UK) Vaillant web sites.

I also found this commercial eBus to USB adapter:

https://www.esera.de/produkte/ebus/1...re-hub-platine

So many options, my head is hurting ...

[dty]

I'd be a bit cautious of using a VR33. I have one and use it to give Evohome OpenTherm control of my boiler. I also monitor eBus (using ebusd) and collect a number of key parameters every 30 seconds. I see some very strange behaviour on the boiler which I'm struggling to believe is commanded by OpenTherm. My current working theory is that the VR33 is doing something weird. Perhaps it's not truly compatible with the UK boiler firmware, hence why it's not officially sold here?

Building an eBus adaptor is not very hard. This is the one I built: https://wiki.fhem.de/wiki/EBUS

You'll find a reasonable list on the ebusd wiki: https://github.com/john30/ebusd/wiki/6.-Hardware

The one I built is the third link (the Prof. Hanning one). Note that the current recommended one seems easier to build.

The ebusd software is a little bit more interesting. If you're lucky, your boiler will already be supported. If not, you'll need to do some experimenting. Plus, when I set mine all up 18 months ago, the VR33 wasn't directly supported, so I had to figure a bunch of stuff out for myself. It's so picky, in fact, that I've left mine alone since I set it up. It works, I get my stats every 30 seconds, and I don't want to run the risk of breaking it.

[OpenMike]

I also monitor eBus (using `ebusd`) and collect a number of key parameters every 30 seconds.

Thanks for the advice. This is exactly what I want to do. Are you using a Raspberry Pi with your adapter?

Also, what connector is needed for eBus on the boiler?

Mike

[dty]

Thanks for the advice. This is exactly what I want to do. Are you using a Raspberry Pi with your adapter?

Yes. The board I built has an RS232 output. In theory, this can connect directly to the RPi, but in practice the Pi has some latency issues with its serial hardware which can cause issues because the timing of requests/response pairs on eBus is surprisingly tight. I ended up using an FTDI RS232 to USB adaptor.

Also, what connector is needed for eBus on the boiler?

I think it might vary from boiler to boiler. On mine, the VR33 connects via a mainboard edge connector, and then there are a pair of screwdown terminals nearby. It is strictly a bus, so it can have multiple devices connected.

Be aware that various GasSafe installers on this forum have said that opening the boiler (even just the mainboard compartment) to add a VR33 or to connect to eBus is against some regs or other and means at a minimum you need to get your boiler tested for leaks. Others have expressed different opinions and/or surprise.

[OpenMike]

OK, well I already have a couple of Pi's running applications here so I think I can handle that. I was leaning towards buying the commercial adapter I linked to above, but I see they are now out of stock.

I've seen that Gas Safe debate on other forums and I don't intend to reopen it here, but as a chartered electrical engineer I fail to see how opening the main board compartment to connect a cable that monitors (not controls) the boiler has any implications on gas safety.

Mike

[GreenGuy]

Instead of using eBus why not use one of your Pi's with a couple of DS18B20 Digital Thermometers attached to the flow and return pipes. It should be cheaper and save any Gas Safe problems.

Michael

[OpenMike]

Hi Michael

That sounds like a good idea, I'll look in to it. My Pi's are busy hosting a web site, backing up files and serving media so I'd need to buy another one

A friend of mine does what you described with an Arduino and thermistors but the response times are a bit laggy.

Mike