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Logamatic 2107 and wall unit: how to adjust.

Last year we purchased a house that has a Buderus boiler with a Logamatic 2107 controller for a radiant heating system on a single zone. In addition we have this wall unit:


The original owners had the moon setting to 1, which kept the house at at a very steady temperature (a drop of only 1C between day and night temps). We like it cooler in the evening, and reset this to a 4C change (and now currently at a 3C change as you can see in the photo). The manual indicates that resetting the day/night change in temperature may also require adjusting other settings in the heating system. But it doesn't say what may need to be adjusted or what effect it has on the system.

We noted last winter that the house took a long time to drop off the temperature at night, and that it never really hit a full 4C drop, except on really cold nights. Good insulation, I'm guessing? I eventually set the night to start at 5pm (to have a noticeable drop by 9pm), and in turn require the day to start at 3:30am in hopes the house would be close to day temperature by 7am.

This is our first experience with radiant heating as well a Buderus (sheesh, it's complicated!). I have the following questions:
1. Is the slow drop and slow rise of indicative of the system?
2. Is there a way to speed up the rise (recover from overnight lower temp)?
3. In the photo of the wall unit - what does HK stand for, and what do the settings do to the heating system?
4. Should the HK be reset any time the moon setting is moved?

Bottom line - we're trying to better understand the system that we now own, and the user manual has the annoying enigmatic "speak with your installer" for the stuff we're tying to understand. We don't want to be blinding messing around with settings on a system that seems to be working pretty well.



  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    Radiant heat, as in radiant heated floors? If so, a 4 C setback is way too much. Even if it is radiators or baseboards, it's too much. The 1 C setback may work if the system is set up for it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GW
    GW Member Posts: 4,618
    I am pretty familiar with this system. I think you’re spending way too much energy thinking about how fast things heat up and cool down. My house is all radiant, I do not yo-yo the thermostat ( I have Tekmar but the principal is the same) at all. Constant circulation, 24 seven. 

    If you want a cooler at night, you’re probably have to spend some money to create a different zone in your bedroom. Or, open up the window for a few minutes

    The HK, don’t know what that means in German, but it tells the BFU sensor which system it is controlling. If you move that from number two, you’ll get an error code (blinking lights)

    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Big Ed_4
    Big Ed_4 Member Posts: 2,523
    HK = hauptkonkakt = main contact
    I have enough experience to know , that I dont know it all
  • robertd
    robertd Member Posts: 4
    :/ Thank you.
  • robertd
    robertd Member Posts: 4
    The wife just said "awesome, that's a f***ing answer!" (She's the one trying to make sense of the manuals.)

    So thank you, gentlemen.
  • TomScott
    TomScott Member Posts: 3
    I'm new to this forum. I have a Buderus oil-fired boiler with Logamatic R2107 and room sensor which was installed several years ago (the installer retired two years ago). I do my own service on the boiler and have personalized the Logamatic R2107 settings which have worked fine - going into day mode and night mode automatically at the prescribed times. Recently, the room sensor appears to stay in day mode even at night when the AUT button on the room sensor is selected. I'm looking for thoughts. Thanks.
  • robertd
    robertd Member Posts: 4
    Check which program you're running. We've had it return to a default program due to a power outage.
  • TomScott
    TomScott Member Posts: 3
    Thank you. Much appreciated. I totally overlooked that possibility. I'll let you know.
  • TomScott
    TomScott Member Posts: 3
    To make a long story short my customized user program was in place but somehow became slightly modified. I changed it back to my program settings. Now, the daytime and night modes appear to change automatically as they should. Thanks again.
  • Neo25
    Neo25 Member Posts: 2