BB (HT-bus) connected but boiler always heats up to the max without needing to

Dear team,

I have a few questions.

1) I have the Junkers ZWBR 30-3 and the old technician had connected two wires in BB (boiler side) which were expanding all the way to the middle of the house (living room) to the main FW-100. I have changed the FW100 with the wired tado thermostat and I did not pay attention to the polarity (if there is such a thing) of the BB cables. No matter how you connect them to the thermostat, as long as they are connected to the very right of the thermostat (+ and - sign as per here), the thermostat should properly be giving info/data back to the boiler, correct?

2) I ran the configuration twice. After the R01, I do not see D17, the thermostat jumps straight to HC01. Is that also normal?

3) Main and important question: The boiler, even if there is no need from the radiators, goes with the tado thermostat all the way up to 67°C (the setting is at position which translates to that temperature).... all the time. Is that normal? With the boiler's own FW100 in the living room, if there was no heating/hot water being needed, it would go down to 30°C (or less). Why does tado keep it all the way up to 70° all the time? This is a total waste of energy!

4) I wish for each smart radiator thermostat to be able to request for heat in the room it requests to do so. Do I have to say in the initial configuration ST instead of R01? Do I make each smart radiator thermostat as a primary one (and if so, how)?

5) In the app I cannot see any info from HT-Bus. It is as if it is analogical. Do you plan on enriching the info you get from bus? Or are these only provided with auto-assist?

P.S: All the radiators have their own smart radiator thermostat. I guess that in case one room needs more of a heating, then the other smart radiator thermostat stay closed and only the one in that room requests from the smart thermostat (linked to the boiler via HT-Bus) to heat up the boiler and circulate hot water (which will only be circulated to that room since all the rest are off. Correct?

Best Answer

  • nickieemp
    Answer ✓

    2) Hmm, third time is a charm apparently, I now see D17. All good.

    3) Question #3, it no longer jumps to 67°. If there is no need the boiler stays calm below that temperature, I need to check again later.

    4) I think it now does. Out of the blue I requested a single room to just ehat up and the thermostat gave the right command back to the boiler. So all good there too, I think. I need to check later.

    5) I think things are provided with auto-assist. Not sure if I spent more than 800 euros to equip my full house with tado° to have less of a feedback that I would wish to have. Maybe an API link would be good.

    P.S.: Think so and hope so.


  • Hello again,

    1) after checking the manual, it says "CÂBLAGE NE DEVANT PAS RESPECTER LA POLARITÉ: Pour un câblage de 2 câbles connectés aux bornes + et -, la polarité n’a pas besoin d’être respectée" So I know now that no matter how I put them, it still works.

    For the rest, I have no answer as of yet.

  • SpaceJetOne
    edited October 2022

    I currently have the same as your point 3) (continuous heating). with Junkers Cerasmart ZSB 7-28. I hope to have to do the configuration 3 times as you... i cross the fingers

    ( it is analog communication in my case )

  • SpaceJetOne
    edited October 2022

    I reconnected the wireless receiver through the boiler using the provided cable and reconfigured using the app. It seems working now. it do not keep heating while not requested. It also do not keep the water in circulation in the pipes.

    I think there was communication issue between thermostat and boiler. i was using a ~10 meter 3G1,5 cable before. (is it not compatible?).

  • I currently have the same as your point 3) (continuous heating). with Junkers Cerapur ZBR 35-3.

    I have a wired connection to the B-B connections but as soon as I start the water just heats up.

    I have D17 in use

    I do not have Hot water in use as do not have hot water only central heating.

    Anyone any ideas ?

  • Can you turn off preheat on the boiler? Otherwise Tado might be able to do it remotely.
  • @Maarten_Leuven this is serious. I would be insisting on all possible channels that they get it fixed. I have not had this behavior so fsr, only in the beginning.