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lmp Member Posts: 1
Does it make sense to install a condensing boiler on a fan coil system in commercial applications?


  • SWEI
    SWEI Member Posts: 7,356
    it frequently can

    Outdoor reset will have it condensing at least some of the time.  A lot depends on the fluid temp requirement at design conditions (coil sizing.)  System balance can make or break the job, so check the current conditions carefully.  If there is a chronically under-heated zone it's only going to get worse if you lower the fluid temp.
  • lisfjoe
    lisfjoe Member Posts: 13

    But won't low water temps in the coil blow cool air? For boilers to condense they need water temps less than 130, right?
  • Zman
    Zman Member Posts: 7,330

    You will always benefit from the turndown ratio of a mod/con. Matching the load will be more efficient than short cycling.

    If you are designing a fan coil system from scratch you should be able to run it at low temps most of the time (outdoor reset).

    If you are retrofitting an existing system you may get cool air at low temps.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SWEI
    SWEI Member Posts: 7,356
    that's exactly how we design them

    Once a fluid temp is picked for the radiant system, we simply tell the coil sizer what there is.  If the air system is on 100% of the time (mandatory air changes) the combination of outdoor reset and a proportionally-controlled coil valve frequently creates conditions where the LAT is only a degree or two different than the room temp.  This allows lower water temps to have greater effectiveness than would be the case with a bang-bang thermostat driving a terminal unit.
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