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Heat link actuator stuck on open

I have one of the actuators on the manifold for my floor heating stuck on open. The zone with the problem has two circuits but only one of them has the "stuck" problem. I don't think this is a wiring issue as I only noticed it recently. Do I need to replace the actuator or is there is it possible to remove it for cleaning and checking the wiring, etc.?


  • Big Ed_4Big Ed_4 Member Posts: 1,095
    Shut off the power to see if there is an short keeping it open ..Warm unit could be another hint ...

    Remove head and check spring loaded plunger valve , try penetrating oil to free up first ... If not replace
    I have enough experience to know , that I dont know it all
  • hot rod_7hot rod_7 Member Posts: 9,112
    As Ed mentioned, often times the small plunger stem under the actuator gets sticky or stuck. Once you remove the actuator and check it for operation by cycling the t-stat, Use the handle end of a screwdriver and see if you can easily push down the actuator pin you see on the manifold, it should be spring loaded and move with minimal effort.

    Thermal actuators can take 3 minutes or more to operate to fully open, look up inside to see the plunger move, and it should also get warm as it heats up to open.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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