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zvc406-exp and hydro-stat 3250

Trying to figure out the correct wiring. My system is an oil fired boiler with tankless DHW coil and a 5 zone radiant setup. I have a circ on the boiler loop and another one on the radiant loop. Looking at the wiring diagrams below I've read that keeping the boiler loop wiring circ on the 3250 will enable me to keep the ODR and low water temp set point for the coil.

Is it correct to wire this using the single circulator on the 3250 wiring diagram? If that's true then my second question on the zvc side is now I will only have 1 pump to wire. If i want this one pump to only operate as the secondary pump option is that possible? Basically I want the radiant pump to operate except when the priority zone calls. The boiler pump will satisfy the priority zone.

Hope this makes sense. Thanks everyone!


https://hydrolevel.com/wp-content/uploads/2015/12/HydroStat-3250-Plus-Inst.-final.pdf (page 4)


  • Zman
    Zman Member Posts: 7,472
    Can you post a drawing of your piping?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    HVACNUT Member Posts: 5,268
    ODR or am Economy setting with a tankless coil.
  • SuperTech
    SuperTech Member Posts: 1,943
    > @HVACNUT said:
    > ODR or am Economy setting with a tankless coil.
    > Nope.

    Agreed. I don't think either outdoor reset or anything that has anything to do with efficiency or economy are designed with usage of a tankless coil in mind, because if someone wants to save money and have an efficient boiler the best thing you can do is ditch the tankless coil.

    What would a reset curve look like when you have to maintain a 150-160 degree low limit? 🤔
  • gaabbee
    gaabbee Member Posts: 43
    HVACNUT said:

    ODR or am Economy setting with a tankless coil.


    I'm sorry, I mis-spoke. The ODR is on the radiant loop not the tankless coil side. I'm not using the 3250 ODR option. My main reason for leaving the boiler circulator on the 3250 is to be able to maintain the low water set point for the coil. Just confused because the zvc instructions show to wire the system pump one way and the 3250 instructions show to keep the system pump wired to it.
  • gaabbee
    gaabbee Member Posts: 43
    edited February 2019

    Here is a very rough drawing some items are left out I just haven't updated it yet. There is the DHW coil inside the boiler (with the 3250) and a hot water fan coil at the top of the picture.
  • gaabbee
    gaabbee Member Posts: 43
    I got off the phone with taco for anyone that searches this with a similar issue. They advised to keep the system pump wired to the 3250 and that I can run the radiant pump as a secondary pump only without issue. Thanks everyone!