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Hypothetical question...on short cycling

SpeyFitter Member Posts: 422
You have a modulating condensing heat source that is larger than the design day load even at its lowest firing rate. It may run for most of the time on design day but it's definately going to be short cycling on shoulder days hindering it's efficiency rates and causing wear & tear on the boiler ignition system & control board.

Your heating load is of the low-temp variety.

Other then a buffer tank, are there any piping strategies that can help mitigate short cycling with an oversized heat source?
Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber


  • ideas

    You'll want to load the boiler heavily every time it is running, so if you have multiple zones, you'll want them to cycle together, if possible...this keeps heat moving out of the boiler when it is firing.  Also, if you can tune the system so the supply temp requirements are all about the same, this will also tend to  keep the water flowing through the complete system whenever the boiler is running keeping loads up.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • Jack
    Jack Member Posts: 1,047
    Seems to me...

    that the best thing to do is take the hit and sell the oversized unit and buy the correct boiler for the application. Anything else you do is a band aid, and further complicates the intial poor equipment selection.

    I'd suggest running the numbers on the material/labor to fix the unfixable vs what it would take to get in and out with a change-out.
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