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Vitodens 200 Boiler pump always on

sbacksback Member Posts: 4
I had a Vitodens 200 WB2B 35 with LLH installed recently. I used the DHW for the past month with no issues and I started testing the heating. The problem is the boiler pump seems to be always on.The boiler pump turns on as soon as I select DHW+Heating on the control panel.

Is this normal? I can't find any working setting that forces the boiler pump to start only when there is heat demand. Apart from this issue, the boiler, LLH, zones, TTs and radiators seem to be working fine. I checked the wiring and I can't see any issue.   


  • CMadatMeCMadatMe Member Posts: 3,066
    No "TT"

    There is no "TT" on the Vitodens 200 as you would see on any other boiler. No the 143 plug is not a "TT". Boiler only cares that it needs to keep a water temp inside the LLH. So if there is suppose to be 130 degree water at the LLH sensor it's gong to fire and run the boiler pump to make sure there is 130 degree water at the LLH. Boiler is not looking for a heat demand it's looking to maintain the required water temp based on the reset curve.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • sbacksback Member Posts: 4

    Thank you for clarifying the 143 connector.

    The issue is the server (primary) pump runs 24/7 even when there is no heat demand.

    Boiler temp: 142F

    Com. Supply Temp (LLH sensor): 142 F

    Outside temp: 80F

    At this point the pump should turn off, but it doesn't.

    However I think I figured it out. I went through the settings again and I noticed that 'Room temp' is set 88F. I changed it to 70F and the primary pump shut down (again no heat demand whatsoever).

    In my opinion the server should stop the primary pump as soon as it notices there is no heat delivery in the system. As a software engineer myself, I would categorize this as a bug.

  • sbacksback Member Posts: 4

    this probably means that as long as the outside temp is lower than the room temp the primary pump will be on, whether there is heat demand or not.
  • CMadatMeCMadatMe Member Posts: 3,066
    No Bug

    Room temp is warm weathe shut down. Once the outdoor temp drops below that your telling the boiler it's time for heat. If your reset curve is properly set the required water temp for that 60 degree day would be rather low. Boiler is going to make sure the system has available to it the required water temp needed./

    If the boiler is not set up and coded correctly it's not the arrow it's the Indian. Have your installer make another visit through the coding..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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