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combi boiler operation question

wklopf
wklopf Member Posts: 44
in Radiant Heating
If a combi boiler has an out-door temp reset and the temps only require boiler water of say, 110 degrees, what happens when there is a DHW call? Does the boiler ramp up to something like 180? Thanks.

Comments

  • hot_rod
    hot_rod Member Posts: 23,398
    Yes, and some will modulate that boiler temperature to just maintain the required DHW flow and temperature.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • flat_twin
    flat_twin Member Posts: 354
    wklopf said:

    If a combi boiler has an out-door temp reset and the temps only require boiler water of say, 110 degrees, what happens when there is a DHW call? Does the boiler ramp up to something like 180? Thanks.


    180 DHW? YIKES! LOL! Probably more like 120 with a combi. I wondered the same when our indirect water heater was installed. What about the temperature swings? No problem going from 90 degree water for space heating to 150 degrees for the indirect and then back to 90.
  • kcopp
    kcopp Member Posts: 4,472
    The IBC DC combi will only ramp up to the set water temp.
    Typically 120-125F.
    No bronze plate HX. no diverter Valve.
    The only Combi that condenses in DHW mode.
  • wklopf
    wklopf Member Posts: 44
    Triangle rates the hot water production of their indirect water heaters at a boiler temp of 200!
  • flat_twin
    flat_twin Member Posts: 354
    wklopf said:

    Triangle rates the hot water production of their indirect water heaters at a boiler temp of 200!

    In the first post the term "Combi" was used. I think of a combi as a modcon boiler and instant (tankless) hot water unit all in one.

    A modcon with built in DHW controls isn't a combi. Yes, those can produce hot water for an indirect water heater at any temp up to the max allowed by the modcon. Specs for indirect water heaters are usually given for a variety of flow rates and boiler water temperatures.

  • gschallert
    gschallert Member Posts: 170
    edited September 2017
    wklopf said:

    Triangle rates the hot water production of their indirect water heaters at a boiler temp of 200!

    "Combi Boilers / Combination Gas Boilers

    Combination Gas Boilers give you Hydrodic Heating and Domestic Hot Water from separate loops within the boiler. Combi Boilers are perfect for when you want on-demand hot water and heating from the same gas boiler."

    Indirect water heaters are entirely different than combi's. An indirect tank is nothing more than another "zone" connected to a boiler.

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