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I thought of sharing my solution to the title; please note that this is valid for my configuration which is Vitodens 200-W, underfloor heating, weather controlled, low loss header (Q70 type) and mixer with separate pump for the heating circuit and that I am not using 100% Viessmann accessories. I am using EM-EA1, mixer and EM-M1, but commands are given by other accessories (room thermostats for the underfloor heating). It may not work for you (depending on specificities of your systems) but it may provide some food for thoughts! Under the initial configuration of the system (same as above less low loss header, mixer and EM-M1, but mixing units on each floor of the house) the on/off command to the boiler (depending on the heating requests from each room, all rooms are zoned and independently controlled) worked OK – in the sense that the boiler and internal pump turned on only when a heating command was sent to the boiler by the room thermostat and turned off when the target temperature in the room was achieved.  The commands are achieved via the D1-D3 connectors in the EM-EA1 and are sent by the room thermostats (but you can use a DIY circuit) and with the boiler set up like this: system on, heating mode off and DHW on.  However, whenever the outside temperature fell under a certain value the internal pump of the boiler turned on, irrespective of whether a heating request was active (antifreeze function, the pump ran through the internal boiler bypass).  I have been told by Viessmann that for my boiler there is no way to make any changes to the antifreeze function … ☹ Further on I Installed a low loss header, mixer and EM-M1 (and got rid of the floor mixing units). I am using the same settings of EM-EA1 and the boiler (heating off, DHW on – time schedule) and now I haven’t seen the antifreeze kick in (same temperatures as before, and even if it does, the boiler pump runs through the low loss header) and when the target temperatures are met the heating circuit pump is off, and so is the boiler pump, irrespective of the outside temperature.  Under the above layout I have seen no issue with the antifreeze function and pumps running all the time – everything is controlled by the room thermostats.  I note that I have no options in the menu for choosing anything for the internal pump (apart from low, max and set running percentages, some useless, as in weather controlled with low loss header the internal pump run at constant speed).  I am thinking that same effects can be achieved for radiators as well, not only underfloor heating, depending on the controls for the radiators and the interface with EM-EA1. Hope you will find this interesting/helpful and all the best! ... Mehr anzeigen

Hi everybody, I would very much appreciate your help in identifying whether the following is normal behavior or whether something can be improved; apologies for the English version, my knowledge of German language is nil. I have an underfloor heating system and the following equipment: Vitodens 200W B2H 32kW (2020/2021, 7 inch color display), Vitocell W100 (200l) – in front of the low loss header, low loss header (ZK03679), 3 way switching valve with electric drive (mixer) and external Grundfos Magna 1 pump for the heating circuit,  EM-EA1 extension (in order to ensure command of the boiler from all zones/room thermostats/three separate distributors - the automation in each distributor is linked to the extension - in DI1/2/3, and standard /comfort/reduced temperatures are all identical in the boiler setup) and EM-MX for the mixer; whether controlled, temperature sensors in the low loss header and after Magna 1 on the flow output. Operating mode of heating is "off" -  as it starts only upon requests for heating from the room thermostats.  After preparation of hot water, the internal pump runs for the time set up in the setup menu (not less than 120s), and then stops.  When it stops, if there is a heating request from any of the zones, the external pump starts (it is off during the hot water preparation phase).  Depending on the flow temperature in the underfloor circuit the burner starts or not. Eventually, as the water in the underfloor circuit is circulated, its temperature decreases and the burner starts – but it stops very quickly, as the water temperature in the heating supply rises sharply, because its temperature is high (after hot water preparation, and it does not decrease while the external pump runs). I have managed to get to a couple of burner starts per day (for heating) but every time hot water is prepared there is this “failed” start – afterwards it works OK, the temperature of the water in the heating supply now decreases (while the internal pump is still off, only with the external pump running) – it’s like the 3 way diverter valve only switches to the heating position and hence letting the water through the low loss header only after a request for heating exists and not at the end of the hot water heating phase. (by the way, what is its implicit position – hot water or heating?) Various values for differential temperature in the low loss header make no difference – currently at 0. Neither is the value of the integral threshold for burner switch-off.  Internal pump speed during hot water preparation -100%, while for heating it is at around 80-90% (and fixed, as per the manual, don’t know the value by heart); heating power is limited for both hot water preparation and heating. To me it looks like the 3 way diverter valve / internal pump management could be (maybe?) better – or maybe I have missed some settings.  I imagine that my setup is quite common - I would then expect to be able to avoid these "false" burner starts... Any thoughts you may have are appreciated and thank you for your time reading this. All the best! ... Mehr anzeigen

Good morning,    I have a 200W model, 2021 edition, with 7" touch display, temperature depending on the external senzor, connected directly to underfloor heating, three zones (pumps), each with several rooms, each room with temperature control.  I understand that it is not possible for this model to turn off the protection and therefore when cold outside the internal pump of the boiler starts (although there is no requeste for heat from any of the areas).  Is there any possibility to lower the threshold of the external temperature at which the internal pump starts?  Leaving aside the fact the the pump has no circuit to run into (as the pumps of the zones do not run in the absence of any heat request from rooms) apart from the internal boiler bypass (the viesmann dealer does not consider necessary to install a low loss header - which would probably help the pump but not solve the issue of the antifreeze protection), I am also wasting electricity... Is there any parameter that can be programmed so as to make this protection start less often (only when outside is minus 15C, for example)? Thank you for your help and please let me know if additional details are needed. All the best! ... Mehr anzeigen