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Buderus Logamatic with TACO Zone Control and Thermostate "C" wire

I have an oil fired Buderus with Logamatic and TACO ZVC406 Zone controller and Sensi WIFI thermostat. I just added the thermostat to a zone and it requires a "C" wire. My other zones and thermostats do not require C wire. There is a C post on the TACO for that zone but what I hadnt noticed before is that the TACO will not always have Power (Power Light is off). When it does C wire is fine, when it doesnt Thermostat drops WIFI. I think what is happening is the Buderus Logamatic for various legit reasons does not always power the TACO and only provides power when it thinks its needed to turn on zones. When Power light goes on, then the zone lights also go on appropriately.
Anyone have an opinion about this Logamatic behavior? Is it working as it should? I would have thought Power on TACO should "always" be on regardless of zones calling for heat. Note: when I put the Logamatic in Manual mode, power goes to the TACO immediately.



  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    its not wired correctly. The zone control should always have power.
  • SuperTech
    SuperTech Member Posts: 2,127
    > @STEVEusaPA said:
    > its not wired correctly. The zone control should always have power.

    Agreed. The zone control should have voltage to it at all times, regardless of the type of control that is operating the boiler. Re-wire it so it's constantly powered, it shouldn't be switched on by the Logamatic.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,538
    Like this
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    HVACNUT Member Posts: 5,765
    Almost exactly like the diagram @Robert O'Brien posted.
    The zone board is constantly powered.
    The ZVC needs to tell the Logamatic to start the burner.
    That signal goes from the ZVC to terminal 63 on the Logamatic.
    On the posted diagram, the zone board connection is at ZC. Your board doesn't have that.
    The bottom left of the ZVC has XX terminals for Pump End Switch. Use that to energize terminal 63.

    I guess the original installer wasn't familiar with the Logamatic.