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Thread: Evohome valve stops working but works fine once removed and put back

  1. #1
    Automated Home Jr Member
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    Jan 2016
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    Default Evohome valve stops working but works fine once removed and put back

    Hi,

    In my home I have a few Evohome HR92 valves and I'm really satisfied with the system, apart from a problem with the one in my living room.
    Before replacing anything I'd like to make sure where the problem is.

    The valve works fine most of the time, but sometimes it stops working and doesn't open any more when it's getting cold. Increasing/decreasing the temperature makes the valve make the normal rotating sound, but the valve doesn't actually rotate so I'm not sure what's happening.

    The thread on the valve is in perfect conditions so I don't see how the motor can rotate without doing anything to the valve.
    The adaptor valve (if I remove the motor body) is very easy to twist with my hands and works fine.

    The weird thing is that, if I remove the valve and put it back immediately without doing anything else, then it just starts working fine and goes on working for a few days.

    Any idea what he problem could be?

  2. #2
    Automated Home Legend paulockenden's Avatar
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    Default

    First thought is that the problem is most likely in the valve that you've attached the HR92 to, rather than the HR92 itself.

    How old is it?

    P.

  3. #3
    Automated Home Guru
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    Nov 2015
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    Quote Originally Posted by mbf82 View Post
    Hi,

    The valve works fine most of the time, but sometimes it stops working and doesn't open anymore when it's getting cold. Increasing/decreasing the temperature makes the valve make the normal rotating sound, but the valve doesn't actually rotate so I'm not sure what's happening.
    When you say the Valve is Making Rotating Sound but not actually rotating how do you determine the Valve is not rotating

    Sounds like may be sticky TRV Body you could swap over the HR92 Head to a different one and see if oproblem persists

  4. #4
    Automated Home Legend
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    Does sound a bit like the pin in the valve body is sticking and not easily returning.

    Valve bodies have a pin with a rubber gasket seal on the bottom end inside the valve a bit like a normal tap that closes the water passage when pushed down, however unlike a tap where you unscrew it to open it there is a spring responsible for pushing it back out again to open the valve.

    If the pin corrodes badly the pin can get "sticky" and be reluctant to return to the fully extended position as the spring doesn't fully overcome the friction of the pin movement.

    When then HR92 tries to open the valve it is raising the tiny little pin you see inside the white screw on adaptor - it's completely up to the spring in the valve body to push the valve pin up to follow it.

    As they have aged some of my valves are starting to go like this now, where they are reluctant to fully open. If you remove the white adaptor completely and try pushing the pin on the valve body down by hand does it seem to come back up again easily ?

    As a workaround you could try going into the HR92 menu and setting option 6, Stroke to 1. Then remove the HR92, turn the black wheel fully anti-clockwise, and refit the HR92, allowing it to perform a calibration.

    Stroke 1 increases how far the HR92 tries to move the pin in both the closing and opening direction - I've found with my troublesome valves that on the default setting it sometimes won't open the valve quite enough so I can't get full output from the radiator - which I only notice in winter. Stroke 1 helps with this but the penalty is shorter battery life.

    Give the stroke setting a try, however even if it does seem to solve the problem it's a sign that you valve body may be on the way out. (I plan to replace mine this summer)

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