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Thread: Weil-McLain Ultra 105 PARAMATER Settings

  1. #1
    DIY Junior Member
    Join Date
    Feb 2008
    New Hampshire

    Default Weil-McLain Ultra 105 PARAMATER Settings

    I have been using my W-M Ultra 2 105 for just over a year. Seems to work fine and because it was added as a replacement to a 1960's W-M when we made an addition doubling our square footage to 2,300 and the gas bill stayed almost the same, we are happy. I have the outdoor temperature sensor installed and it does adjust the Outlet water temp, but I have to wonder, are the default settings of 190 the best or should I drop it to 150 and let it adjust itself based on call to whatever? It must cost me more to heat to 190 every time? Thanks

  2. #2


    I am not sure exaclty how your unit works. My buderus has a line that sets the output temperature based on a temp of 14 and 60 degrees out side. the default was 190 for mine at 14 degrees. I would advise droping it 5 degrees and see if you still have adaquate heat if so drop it another five. You are correct that it cost more to heat the water hotter


  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    This is a problem with these high-tech devices, the installers may not know how to gain the maximum efficiency out of them, and they operate as an old unit (although at greater efficiency). The great thing about these modulating boilers is that they can increase their efficieny above the full-output value to nearly 100% if they are running at low heat outputs; it is more efficient getting the heat out of the burner at lower fire rates). Without knowing the design parameters of that particular unit, it's hard to tell.

    Often, though, you set a threshold temperature, then if the boiler finds it needs to run a lot, it ramps up the boiler temperature.

    Keep in mind, that as you lower the supply temperature, the amount of heat you can extract from the radiators does not decrease quite linearly - as the temp approaches the room, it becomes less efficient.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4


    I agree that a lower temp in the baseboards decreases transfer efficiency. But it does not matter, A good modulating boiler will just modulate down to only produce the amount of BTU's needed by house. you will still get the added efficiency of producing lower temperature water. If at all possible low enough to get the boiler to condense



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