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TRV head "hissing" when between 3 and 4.

skiereric
skiereric Member Posts: 55
in Radiant Heating
I have added a few TRV heads to existing TRV valves.

Strangely, a couple of my TRV heads hiss when set above 3 but less than 4.

I am confused why this is occurring.

This is the head in question - https://herzvalves.com/catalog.php?prodID=5&lng=gbr

Any idea what could be causing this?


Comments

  • skiereric
    skiereric Member Posts: 55
    I also hear this sound on non TRV rads when the lockshield is partially open.
  • bburd
    bburd Member Posts: 646
    edited February 2022
    The hissing is caused by the differential pressure across the constricted opening in a partially throttled valve. Some systems have a supply-return bypass or a variable speed (ECM) circulator to minimize this problem.
    —
    Bburd
  • skiereric
    skiereric Member Posts: 55
    I guess said differently, is this a problem or just a sound annoyance?
  • bburd
    bburd Member Posts: 646
    edited February 2022
    Usually it’s just an annoyance if you only have a few TRVs on the system. Over time it may shorten the life of the TRVs.

    In systems where most or all radiators have closed TRVs and the circulator has a steep performance curve, high pressure may force the TRVs open, leading to overheating. The usual fix is to install a circulator that is compatible with TRVs (flat performance curve) or some form of differential pressure regulation.
    —
    Bburd

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