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Thread: Can't get one zone to heat up

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  1. #1
    Automated Home Jr Member
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    May 2021
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    Question Can't get one zone to heat up

    Hi, I've had evohome hr92 trvs on most of my radiators for about a week now, on the whole it's been working well except I just can't get my daughters bedroom to warm up fully, even if I have her target temp set to 35 degrees the system status on the controller only shows 17% demand for her zone and the valve position on the trv itself is 58%. The rad does warm up but it doesn't get as hot as it would do if I take the head off and manually open the valve

    I dont understand why the demand and/or valve position doesn't go to 100% when the room is only measuring 20 degrees with a target of 35. I've tried deleting the zone and re-adding it, even tried a completely different hr92 but for some reason I just can't get that radiator to run at full chat.

    By the way, I'm not using opentherm, the boiler is still being controlled by the old controller, so although the demand may only show 17%, this doesn't have any bearing on boiler output.

    Anyone got any ideas?
    Last edited by therealfronty; 18th May 2021 at 09:45 PM.

  2. #2
    Automated Home Jr Member
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    When you refit the HR92, you do make sure you turn the black part of the body fully open for the HR92 to recalibrate.
    Have you tried swapping the HR92 with another one to see if the problem moves to the other room.

  3. #3
    Automated Home Legend
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    Quote Originally Posted by Billywizzo View Post
    When you refit the HR92, you do make sure you turn the black part of the body fully open for the HR92 to recalibrate.
    Have you tried swapping the HR92 with another one to see if the problem moves to the other room.
    I had something similar when a room was decorated and the decorator caught the HR92 on a radiator. It showed the temperature in the room at 35c as did the Panel. It wasn't of course. I tried to override it but it reverted back to this. I resolved it by taking the batteries out of the HR92 for a few minutes, then put them back and fitted the HR92 after first fully opening the valve. Problem went.

  4. #4
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    If you have the latest firmware, it could be the Load Scaling that is causing this.

  5. #5
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    Quote Originally Posted by bruce_miranda View Post
    If you have the latest firmware, it could be the Load Scaling that is causing this.
    Indeed. If load scaling is on "Normal" try changing it to "Partial", or even off.

  6. #6
    Automated Home Jr Member
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    Not sure what load scaling is, I've got firmware 02.00.19.33 and have disabled both cold start/warm boost or whatever it's called straight away as didn't want any clever nonsense going on.

    Anyway, there is something weird going on, when the hr92 shows valve position 58%, if I take the head off I can't actually manually open the valve any more, it is already fully open, so it seems the head is reaching the 100% open point maybe earlier than its expecting (although not sure why it doesn't report 100% in that case)? So I was just having a play, and if I set valve stroke to 1, it then reports the valve position as 100% (when fully open), and also sends that back to the controller, I can see the demand for that zone goes up to 100%.

    When demand is 0, it does fully close the valve regardless of whether I set the valve stroke to 1 or 0, but it seems that on 0 it's not reporting the valve as fully open even though it is. The valve body is a TRV4 and most of my other rads are fitted with these and don't have any problems reporting the fully open valve position, so not sure why this one is different. Have left valve stroke set to 1 for now so at least in system summary I can see 100% when fully open. I need to check the temps in that room again as there might be something else going on if the valve was fully open anyway. All very odd.

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