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Thread: Evohome HR92 TRV having problems

  1. #1
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    Default Evohome HR92 TRV having problems

    Hi,

    I just installed an Evohome system but one of the TRV's is acting strange.

    First of all when locking the HR92 on the valve it doesn't always CYCL, but even when it does the valve position jumps from 100 immediately to 43, the goes step by step to 19 and then jumps again to 0 ?

    Once this is done and I set a new temperature I only hear the motor for a sub second instead of several seconds ?

    BTW, is it normal that I can push the pin in the HR92 head (when detached) back and forth ?

  2. #2
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    Quote Originally Posted by DarkV View Post
    Hi,

    I just installed an Evohome system but one of the TRV's is acting strange.

    First of all when locking the HR92 on the valve it doesn't always CYCL, but even when it does the valve position jumps from 100 immediately to 43, the goes step by step to 19 and then jumps again to 0 ?

    Once this is done and I set a new temperature I only hear the motor for a sub second instead of several seconds ?

    BTW, is it normal that I can push the pin in the HR92 head (when detached) back and forth ?
    Are you making sure to turn the black wheel fully anti-clockwise (open) before attaching the HR92 ?

    When you first close the latch it's normal for the reported valve pin position to suddenly jump in value (if you happen to already be displaying valve pin position with option 10) because closing the latch will clear any previous calibration in preparation to do a new valve pin position calibration, and at that point it doesn't know where it is.

    What should happen is after about a minute it goes into cycl mode and you'll see the number dropping, when the motor stops turning it will go from whatever value it was reporting directly to zero - that's normal and that is it calibrating the fully closed position, and it then starts counting upwards from that point next time it opens.

    Next time it opens wide based on heat demand it will count up and if it hits the limit stop before it counts to 100 it will make an adjustment to jump directly to 100 and scale the calibration based on that. So it won't be fully calibrated until it has fully closed and fully opened at least once.

    If you're not seeing cycl appear after a minute then you're either not unwinding the black wheel (so when it tries to wind the pin down it's already down - if it doesn't wind for at least a couple of seconds cycl won't appear on the display) or the switch on the latch has a fault. (I think someone has reported a faulty latch switch once before but it's certainly not common)

  3. #3
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    Yes, the black wheel is fully open.

    The first problem is that when it goes into CYCL mode it sounds like it isn't going "all the way"... normally the sound of the motor changes when reaching the end (fully closed) as it gets heavier resistance... but this isn't the case with this TRV (it stops way in advance).

    Second problem is that after the CYCL mode and requesting more/less heat you only hear the motor for a sub-second (causing it to probably turn the black wheel only a few millimeters which doesn't have any impact on the valve, ie. it doesn't open/close as it should be).

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    Are you sure the pin isn't seized on the valve body ? Can you press it down by hand ? (Push down on the side of a large flat blade screw driver as pushing it directly with your thumb would be difficult) Also try the same test on another valve body which is working OK to see how much force is required there.

    Have you tried swapping another HR92 onto that valve body to see if it's OK or whether it also struggles ? That's probably the first thing I would have checked.

    You could try setting Stroke mode to 1 which increases the force of the motor but it sounds to me a bit like a valve pin that is seizing or perhaps not compatible. (Pin too long etc)

    Are all your valve bodies around the house the same kind and about the same age or is this one different ?

  5. #5
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    No, it isn't a radiator problem as another TRV works fine on it.

    The problematic TRV also has the issue on another radiator.

    All radiators are equal... and the pin is 14 mm as it should be.

    How do I set stroke mode 1 ? Which setting number is this ?

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    Quote Originally Posted by DarkV View Post
    No, it isn't a radiator problem as another TRV works fine on it.

    The problematic TRV also has the issue on another radiator.

    All radiators are equal... and the pin is 14 mm as it should be.

    How do I set stroke mode 1 ? Which setting number is this ?
    I think Stroke is setting 6, but to be honest from what you say above it's pretty clear you've got a faulty HR92.

    Send it back for a replacement under warranty.

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    I had the same conclusion but nice to see it confirmed.

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