How to wire wired v3+ thermostat to bulex thermomaster f29e in opentherm?

Vincent1994

Hi everyone,

I’m hoping to get some help with wiring my Tado V3+ thermostat to my Bulex ThermoMaster F29E using OpenTherm. I’ve searched through the community, YouTube, and Reddit for answers, but I’m still confused. I live in Belgium, so I have the EU version of both the thermostat and boiler.

We recently moved into our house, and since it’s getting colder, we wanted to fix the previously broken thermostat. After some research, we decided to go with Tado. I really like the app and instructions, but they didn’t seem to fully resolve the issue. I wasn’t able to get it working at all (you’ll see why in a bit 🥲).

I installed all the TRVs and set up the thermostat, only to find that the Bulex boiler was running at full blast constantly, which didn’t seem right. After troubleshooting the installation and doing some research, I opened the Bulex the next day to see what was happening. And—surprise!—the thermostat wires weren’t connected to the boiler at all 🥲😅. I assume the previous owners disconnected it because the original thermostat was broken and couldn’t be used. So, that explains why it wasn’t working—great, now I know!

However, now I’m not sure how to connect everything correctly. Being the instructions of tado only go so far as replacing the thermostat itself. I’d really appreciate any advice or second opinions on how to proceed.

The previous thermostat was a Honeywell CM907, connected as shown in the attached picture of the wiring label: A to L, B to N, and the ground wire wasn’t connected to anything.

Currently, the thermostat is connected as follows:
• Blue (N) to NO,
• Brown (L) to COM,
• Ground wire parked in P2.

I’ve also attached a picture of the current setup.

According to the Bulex manual, the OpenTherm terminals are 11 and 12, which is also labeled on the boiler (see pictures for reference).

I’ve included a few pages from the manual, wiring schemes, and pictures of the back of the circuit board and terminals. Hopefully, I’ve provided enough information for you to help me figure this out. I’m fairly handy, so with your advice, I’m hoping to fix this and avoid being cold this winter! 😂

Thanks in advance for your help and any advice from others reading this!

Rob

@Vincent1994

I see you are making progress. The following is needed for the boiler:

• Bridge the Relay connection on the boiler. You've already done this.
• Connect the thermostat wires to 11 and 12. Also already done.
• Remove the wire bridge for Opentherm. This is not yet done.

I am curious what is connected to the eBus connectors (5 and 6, same picture as Opentherm wiring) though. Where are those two wires going?

After removing the Opentherm wire bridge, you're done on the boiler side. The issue then remains is on the tado side. Your wiring on the tado stat is for relay and the thermostat is also configured as relay, so it won't work as an Opentherm thermostat this way.

I have just changed the configuration of the thermostat to Opentherm. It however will not work until you change the wiring on the thermostat side to + and -. Colour/order of the wires does not matter, as long as it are the same wires that are connected to 11 and 12 in the boiler. After connection, please do give the system 15-ish minutes before you start testing.

One disclaimer:

My documentation mentions "Bulex version delivered with OpenTherm interface card (NL)". You are not in the Netherlands though. I do see the Opentherm connectors, so I presume you also have it. If you don't, then we could use the Vaillant eBus modulating bus as well. Which would require some minor rewiring and reconfiguration on our side. But just try what I wrote before 'disclaimer' first.

Vincent1994

@Rob

Thanks for the swift answer, appreciate it!

I added a an image of the manual aswel as the backplate showing were the wires are going down below where I noted in blue (ebus) purple (opent). Thes e wires all go to a ebus card (number 16 on the legenda) .

When you write « Connect the thermostat wires to 11 and 12. Also already done. » you mean i assume: remove the blue bridge and then connect my wires my - in this case blue and brown wires - coming from the thermostat (which are also drawn on the backplate image )? Just to be sure.

Correct im in belgium i do not have the opentherm card as i didnt buy the machine. Maybe the card has been thrown away. The card built in on this one is an ebus card, looking at the manual.

Greets

Vincent

Rob

I think you do have the Opentherm card installed in your boiler, as I see that the system is working and I'm seeing Opentherm communication since roughly your last reply. I think this has fixed it.

Vincent1994

Hi rob,

Thanks alot for the help!

I hope other people can find some information here.

The setup as it is now:

Wired thermostat is wired : Blue to -, brown to +, Green/yellow(earth) to P2.
Following the suggestions of rob the colors dont matter here

At the Bulex machine's backplate I connected the blue and brown to 12 and 11 (you can find this in the images above here)

The Thermostat has to be set to Opentherm. This can be set remotely by Tado but als through the Tado pro app.

Peace for now