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Does Hydrostat Circ-Hold Help or Hinder Atmospheric Boiler Protection?

D107 Member Posts: 1,849
I have seen varying opinions on the Wall as to whether Hydrostat's Circ-Hold feature helps to prevent atmospheric boiler corrosion from low-temp system return water. It will allow circulator to run only upon boiler temp reaching 125º, and will stop circulator when boiler temp reaches 114º. Some credit it with helping to prevent the corrosion while others say by having the circ going on and off it prolongs the amount of time the boiler is subject to the low temp water returns. (This question is asked assuming there is no other boiler protection such as a bypass or a three-way valve/bypass, etc.)


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Sure it helps. With a large water content system, you will see a lot of on-off of the circ from a cold start.
    Piped bypass would be better.
  • hot_rod
    hot_rod Member Posts: 21,858
    Sometimes called a bang/ bang protection method.

    It would cycle the circulator quite a bit on high mass systems as @STEVEusaPA mentioned.

    Better method is to "slip the clutch"
    A thermostatic valve, motorized valve, injection mixing are all smoother ways to accomplish the task.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream