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Danfoss TRV is leaking - which part do I replace?

I have a 1-pipe steam system in my home. Several years ago I installed Danfoss TRVs in a few of the rooms that overheated, and they've worked great - until now. I’m hearing a slight hiss from the vent when it's supposed to be off. When I place my finger over the vent hole, the noise stops. When I dial the TRV operator to higher numbers, the slight hiss becomes a loud one. Now, the TRV actually consists of several components - which of them should I replace? Is possible to fix the problem or do I need to buy a whole new one? Thanks for everyone's help.


  • Slight hisssssss

    Check your pressure, and make it as low as possible. Possibly your pigtail has become clogged, and unable to allow the pressuretrol to feel the pressure.

    Temperature setbacks may cause this during recovery as well--NBC
  • gmusser
    gmusser Member Posts: 5
    Pressure doesn’t seem the issue

    I'm using a vaporstat, and the pressure is very low. But yes, it does seem to arise during setback recovery. Why is that?