Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

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

D107D107 Member Posts: 1,686
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.)


  • STEVEusaPASTEVEusaPA Member Posts: 4,209
    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_rodhot_rod Member Posts: 13,509
    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
    The magic is in hydronics, and hydronics is in me
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!