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short cycling

shakey27 Member Posts: 1
edited October 2015 in Domestic Hot Water
I have a three zone boiler. One zone is radiators, one is fin tube and the other is in floor. when the in floor runs on it's own the boiler gets to temperature the zone is heating as it is supposed to. But the boiler starts up about every 10- 15 min. rubs for 2-3 min. and gets to temp again. This cycle happens until the in floor zone is satisfied. What could cause this.


  • Zman
    Zman Member Posts: 7,579
    Your tubing can not get rid of the energy as fast as the boiler can produce it. The boiler is set up to turn on at one temp and turn off at another. You may be able to increase this differential in the boiler settings.
    The cycles you describe are not ideal. They are not extremely short either.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    ...and/or you may need to consider a buffer tank and some re-piping...

    There was an error rendering this rich post.

  • hot_rod
    hot_rod Member Posts: 22,271
    what type of boiler? If it is cast iron or copper tube, non condensing, that is too short of a run cycle and problems will arise.

    As mentioned the boiler has more output than a single zone can distribute.

    Ideally you would run a heat load calculation for the home and confirm the boiler is sized close to that load number.

    Here is a free ap from SlantFin to help with that important first step. Report back your findings.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream