Extension kit with Glow-worm Ultracom 30CXi

Extension Kit eBUS mode & Glow-worm Ultracom 30CXi - all help greatly appreciated!

I've had the Tado system working with the Wireless Receiver for a short while but wanted to take full advantage of the boilers modulating capabilities which means having it connected via eBUS rather than relay. As such, I did some research, bought the Extension Kit and wired it in today.

For eBUS the boiler apparently requires 0v and 24v to be bridged -as shown in attached pic. The Extension Kit has paired successfully and shows up in the App. The boiler knows there's an external controller connected as it shows "Ext" on its display. I've changed all the Tado devices to request heat from the new box.

Programming the new Extension Kit as an eBUS controller from the Wireless Thermostat (as shown in the pic) fails every time, and I've tried over and over. Despite multiple Tado TRVs calling for heat the box simply refuses to play ball.

I've had to give up for the day and swap the wiring over to relay mode. This has got the heating up and running which at least proves the box is working. Really hoping that somebody can shed some light on the problem. :-)

Best Answer

  • Chris_L
    Answer ✓

    Pretty sure I've got it sorted!

    The solution was to pretend I was swapping out a compatible Glow-worm eBUS controller (in this case a Climapro1 RF) and run through the installation sequence in the App which successfully programmed the Extension Kit.

    I still have no idea why it won't accept eBUS mode programming from the engineers menu on the Wireless Thermostat, but at least it's job done! :-)


  • Still no joy getting eBUS to work. The Extension Kit simply refuses to save Vaillant/Glow-worm eBUS settings (D07 - or D05 for that matter), showing FAIL at the end of the setup process.

    My Glow-worm Ultracom 30CXi has eBUS connections. The Extension Kit (firmware version 81.1) is supposed to support Vaillant/Glow-worm eBUS. All the wiring (AFAIK) is correct, including the 0v/24v bridge. I'm in the UK, so there aren't any Opentherm modules - it's a straightforward 2-wire (plus and minus) connection directly from the boiler to the Extension Kit.

    Anyone have any thoughts as to what's wrong?

  • Hi Chris

    Did you ever get this working ? I have a Glow-Worm Betacom2 with eBus and would like the modulation working too.

  • Hi Jon_B

    I had to buy the "Extension Kit" to replace the Wireless Receiver that came with the kit. My problem above was due to:

    Being a combi, with hot water controlled directly from the boiler I had attempted to disable hot water control (HWX) in the Tado install menu. The setting failed because the driver for my boiler (D07) requires the hot water setting to be ALWAYS enabled - disabling it caused it to throw a wobbler!

    The boiler works, and modulates perfectly. Hot tap water (as before) continues to be controlled directly by the boiler.

    On another note, I would say that the temp sensors in the TRVs are pretty bad - even adjusting them with an offset. I would highly recommend getting a "Wireless Temperature Sensor" or "Smart Thermostat" for each room to monitor temperature. Either will work - just get whichever is available cheapest! The heating has been trouble free ever since. It's Black Friday week so is probably a good time to grab some. :-)

  • Brilliant thanks for this, I’m in exactly the same situation with my boiler so now I know what to do !

    Tado told me I would be ok and wouldn’t even need to open up the boiler ! But there you go. Off to eBay for the extension kit !

    I already have the wireless smart thermostat so should be all good, thanks again ,

  • Chris_L
    edited November 2021

    No prob Jon. :-)

    I mention the room stats because you can actually put one in every room that has a rad and a Tado TRV. They're on the expensive side but solved all the problems of the Tado TRV sensors being too close to the rads to give accurate readings. The "offset" feature in the app helps a bit... but not completely.

    If your old stat was digital on the eBUS you shouldn't need to open up the boiler. If it was a simple relay you might need to pull the wiring cartridge out of the boiler & swap a couple of wires. It's an easy job but the cartridge might require a bit of a YANK to get it out.

  • Hey Chris (maybe Jon),

    Thanks a lot for documenting your process here. I recently switched my boiler (ultracom2 30cxi) over to ebus and this post helped me figure it out.

    Please forgive this reply over a year since the initial comment, but I was wondering if you had lost control of the hot water temp after doing this? I hadn’t realised but when running my hands under the hot water I noticed it was a lot hotter than the pre-ebus setup and sure enough, it’s stuck at 55 and doesn’t change when hitting the DHW up/down keys. In these times, I’m keen to get that lower and try save the boiler heating the water way hotter than it needs.

  • What happens when you change the hot water temperature in the app?
  • There’s no option to set the temperature for the hot water (that I can see anyway). It’s simply an on/off toggle.
  • JakeT91 - sorry, I can't help you. Hot water on/off & temp control remained on the boiler. Maybe try running through the control unit setup again but select "HW X" - that might remove it from the App & return it to the boiler's panel.

    I don't have the Ultracom boiler any more - it was "beyond economic repair" and I now have an Ideal boiler.

  • @JakeT91 I’m assuming you have a combi? check that you’ve set it correctly for ebus with hot water control - you should then get the option to set hot water temperature in the app. At the moment it sounds like it’s set for relay hot water control.
  • Thanks a lot for the suggestions and comments, I do indeed have a combi. After turning off the hot water control (by selecting HW X) and re-enabling it, I now see a temperature slider for the hot water control in the app and the desired temperature reflects on the LCD on the front of the boiler. I did click ‘update firmware’ on each of the devices which had it available prior to doing it so perhaps that’s the reason it’s now working as expected.
  • Hi Chris,

    Took the plunge and bought an extension kit off ebay. My boiler is Glowworm SXI 170 but is the exact same wiring as yours. Have wired exactly as in your diagram "ebus setup fails" but enabled hot water on the thermostat setup. Everything is connected in the app, front of boiler is showing "ext" but when i call for heating nothing happens. Did you have to do anything else you haven't mentioned on here ?

  • I don't think so but, honestly, can't remember. I don't even have the GlowWorm any more.

    My only thought is: Did you remember to bridge the 24v and 0v connections with a link wire?