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Water Source HP loop with Viessman Boiler

Has anyone ever set up a Viessmann Vitoden 200 boiler with a water source heat pump loop? How did you set up the controls? Viessmann has some fancy controls, but most of it is useless in this situation since I wont be using outdoor reset. 1 1/2" is used for the boiler loop, but I need to control the water loop temperature of the primary loop (4"), not the boiler supply temp.

So this is what I gathered but am unsure if this is the best method...

I saw they do have a flow temp. sensor which I can hook up to the boiler and use in conjunction with the viessmann extension module ( but the flow temp sensor is made to be used with the low loss header). With this module, I think I can use the buildings external controls on the inputs on the extension module to turn the boiler on and off. I then can set up the boiler's controls to do external demand with set flow temperature (with a sensor on the primary loop to sense the primary loop flow temperature).

However, does anyone know what type of flow temperature sensor is used with the Viessmann boiler (i.e. 10k ohm). Then I can use just a honeywell sensor in an immersion well on the primary loop as Viessmann's temp sensor won't exactly work in the primary loop (unless they have a strap on sensor to go around 4" pipe).

Does anyone else have experience with this? What did you do?


  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,290
    First....What water temp does the system need? Does it do domestic hot water production also?
  • platestealer
    platestealer Member Posts: 4
    The system needs ~68 F. The current boiler goes on at 63 and off at 75 F.

    There will be no dhw at this point from the boiler.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,290
    Shouldn't be much different than what we do with pellet or wood fired equipment.
    Assuming you have a primary loop on the Viessmann, you can just drop the alternate heat source into that. When Das Viessmann calls for "heat" it will sense the loop is already at temperature and remain off as if temp demand was satisfied.

    What in the world are you running with 68* water temps?