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heating curve

First of all I would like to thank the many responses I got last year as I was deciding to put my system in.I had a contractor do the install. I went with a buderus ga124 boiler, indirect tank with a r2107 controller,panel rads upstairs with room sensor and baseboard downstairs. My question is what is the heating curve and how does it affect water temp. Also, I read an article that said the panel rads(w/trvs)will "sip" the hot water from the boiler. Can anyone explain this to me.thank you, Bob


  • Joe@buderus_2
    Joe@buderus_2 Member Posts: 302
    Heat Curve

    The heating curve set point is a "guide" to what temperature should be running through the system based on the outdoor temperature. On mild days, 180 degree water may not be needed to heat the home. Heating the system water temperature to less than 180 degrees saves fuel. The Room Sensor will help adjust the system water temperature based on the indoor temperature as well.
    If the Panel Radiators have a thermostatic valve, then the thermostatic valve will open and close automatically allow flow into the Panel Radiator. If there are any questions about programming the R2107 please contact us at 1-800-283-3787 while you are in front of the control and we can assist.
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    The Heating Curve

    is a mathematical slope when graphed. It represents the degree in change of your boiler supply water temperature relative to the outdoor temperature. In simplest terms it is the best way to have your radiator output match your heat loss at any given outdoor temperature.

    With an indoor temperature at, oh, 68 degrees, say you have radiators that need 180 degrees on a zero degree day.

    For example, when the outdoor temperature is near room temperature (say 60 to 65 degrees allowing that solar and internal gains make up the difference), your heat loss would be zero. Hence your hot water temperature would also be at about 70 degrees. When all of those numbers intersect, your heat input is zero because your temperature differentials are zero.

    When the outdoor temperature is zero out you need 180 degrees as stated above. At that point, your radiator output still matches your (larger) heat loss.

    The slope ratio is what defines the heating curve. It is somewhat linear in it's simplest form but does in fact curve to account for emitter types, empirical internal and solar gains, mass of the building... take a look. Such curves should have been provided.

    Now to your particular needs, do you know what your emitters are designed for? If radiant panels, they may require 140 degree or lower water. That or the highest requirement sets the highest curve value and it modulates downward from there.

    TRV's sipping water: How true that is.. TRV's respond to the immediate room needs. They modulate well and when the room is cold it is right there with just the right amount of hot water necessary.

    A radiator may have a design output of 5,000 BTUH (say 0.50 GPM flow at a 20 degree drop). But the radiator has been warmed, the sun is shining on that side and you have the neighborhood over doing the "Antler Dance" behind closed shades....it is -5 degrees out and a little heat is needed so the valve opens so slightly and takes in 0.10 GPM. If that does not heat the room it opens more... fractionally what the radiator would normally draw. In so doing this, it reserves excess flow for the other radiators on the north side that may need it more. How cool is that.
  • Jed_2
    Jed_2 Member Posts: 781
    So Commercial, while Brad

    is so eloquent!


    p.s. Happy Birthday!
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    Brad IS eloquent.....

    But seldom does he have to program a Buderus 2107 control.(no slam here....just the facts!)

    Joe, on the other hand...deals with this control pretty much exclusively, and would amaze you with the speed he can program and effect differences with this particular control.

    Trust me. I've worked extensively with the folks from Buderus and before they sit in front of a phone to answer questions...they know the answers! Certain situations need certain attention, and these guys can point us in the right direction PROMPTLY...as oppsed to guessing.

    They're there to "SUPPORT" their product and TEACH both the field tech. AND the homeowner. I've had homeowners teach me things about their system settings...many times. They LEARNED them by calling and doing their own special programs with the technical help directly from the factory techs. that answered the phones.

    I wish I could know their product as well as any of them!Fortunately/Unfortunately, I only have to deal with them sporadically...at best! (the buggers rarely ever fail, and when they do...they hold the program for so long..that they don't need to be re-programmed!)

    I will be going back to see Ed Sullivan again soon.(training guy extrordinaire!) I've been to the class twice in 6 years, and still can't retain ALL the information that they provide. Ed's cheat sheets are great!...but when it comes to the real nuts and bolts of the controls, sometimes the factory is the BEST resource. That's what they do. Chris
  • Jed_2
    Jed_2 Member Posts: 781
    BUT, Chris

    the question was theoretical. It had nothing to do with the Logomatic, which I'm sure uses the same or similar algorithms. Just commercial hawking of a theoretical question, IMHO.

  • Brad White_9
    Brad White_9 Member Posts: 2,440
    No slam taken....

    I took it as a theoretical question but I am never the last word on anything....(at my age, I mean, now, really... ;)

    I certainly know that if barefoot bob needs programming particulars, Buderus will provide ample assistance! They may ever get him a pair of shoes.....
  • Jed_2
    Jed_2 Member Posts: 781
    My bad

    i simply overlooked the r2107 control inherent in the question.


  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    Sorry Jed...

    Just goes to prove...Here in cyberspace...we can't see bodily gestures and/or read intimated inflection into written words.

    Maybe Mr. Holohan will be working on some sort of a video post/rebutal source in the future...

    No pressure Dan!(please know, I'm just kiddding!) Chris
  • Brad White_123
    Brad White_123 Member Posts: 5
    And just what IS

    a 2107 anyway...? :)

  • Bob LaRochelle
    Bob LaRochelle Member Posts: 13
    shoes or skis

    Thanks for the info guys, there's obviously going to be a learning curve along with the heat curve. It's going down to 41 so the system will turn on. I know this sounds strange but I'm looking forward to the heating season so I can see how this system works. I actually got my nickname because I barefoot waterski.
    thanks again, Bob
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