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Thread: HR92 wildly inaccurate

  1. #1
    Automated Home Jr Member
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    Exclamation HR92 wildly inaccurate

    Hi

    I have a new HR92 on a radiator that is reporting very confusing temperatures and hence very variable heating. Others in the house work fine.

    I put a Sanus digital thermostat on top of the HR92 to compare the readings as closely as possible. Here's a sample:

    HR92__Sanus
    17_____19.5
    17_____22.5
    20_____18.5
    20_____23.5

    Readings from analogue thermometers and the feel of the room generally agree with the Sanus

    The difference is not a constant or even in the same direction so using the calibration offset isn't going to help.

    Any solutions or shall I just get a replacement?
    Last edited by jbuller; 14th February 2021 at 12:01 PM.

  2. #2
    Automated Home Guru
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    Temperatures measured close up to the radiator are influenced by the temperature of the radiator and will only reach equilibrium once the room and radiator have reached stable temperature. The degree of offset at any given time will potentially be affected by such things as air flow around the valve, design of the radiator and thermal coupling between pipework and valve, which could vary between makes of valve body? The HR92 and Sanus will be affected differently as the Sanus is not in contact with the pipework and even a small difference in location could affect air temperature. I have installed separate room thermostats in most places as these give far more consistent control and can be located where you want the accurate temperature. Not cheap though.

  3. #3
    Automated Home Jr Member
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    Quote Originally Posted by jbuller View Post
    Hi

    I have a new HR92 on a radiator that is reporting very confusing temperatures and hence very variable heating. Others in the house work fine.

    I put a Sanus digital thermostat on top of the HR92 to compare the readings as closely as possible. Here's a sample:

    HR92__Sanus
    17_____19.5
    17_____22.5
    20_____18.5
    20_____23.5

    Readings from analogue thermometers and the feel of the room generally agree with the Sanus

    The difference is not a constant or even in the same direction so using the calibration offset isn't going to help.

    Any solutions or shall I just get a replacement?
    To rule out any Radiator effect, check the calibration with the HR92 removed from Radiator and both placed in a nice neutral position.

  4. #4
    Automated Home Legend
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    What CT1 said.

    Sitting another thermometer on top of the HR92 as a comparison is meaningless because it is being heated by the radiator pipe work below and the side of the radiator differently to the HR92.

    All that matters is how the HR92 compares to true room temperature measured at a distance. So put the Sanus out into the room on a coffee table or similar, let the room temperature stabilise (ideally doors/windows closed) and compare it to what the HR92 is set to and reports.

    If there is a fairly constant offset error, adjust the calibration setting on the HR92. It defaults to 0C but -1C is typically more appropriate. If the HR92 (or control panel) report higher than the true room temperature measured by the independent thermometer adjust the calibrate setting on the HR92 in the negative direction then wait an hour or so for the room to stabilise at the new temperature.

    If the error varies a lot in different conditions or you seem to need more then -2C calibration set in the HR92 you probably need to use a remote wall sensor to get accurate control of that particular room.

    This can be due to many factors including room layout, furnishings, drapes near the HR92 or obstructions to free air flow along the floor, radiator design, (convector or not, side covers fitted or not) whether the HR92 is mounted on the hot or "cold" end of the radiator etc... in some configurations you just can't get accurate control of the room temperature by measuring beside the radiator.

    There is nothing wrong with the temperature sensors in the HR92 - they are actually very precise, however they are in a location that is directly heated by the radiator so this limits their ultimate accuracy, and if there isn't good convection past the HR92 they can potentially be out by several degrees due to localised heating.
    Last edited by DBMandrake; 16th February 2021 at 02:46 PM.

  5. #5
    Automated Home Jr Member
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    To follow up on this.
    I bought another HR92
    Placing it next to the horizontally mounted existing HR92 (wedged between it and the wall) its readings generally agreed with the Sanus and analogue thermometers nearby, not the existing HR92.
    Swapping them over to use the new one has resulted in a much more reliable and comfortable heating regime, again agreeing with the other thermometers while the old one still deviated.

    Here's the Domoticz read out for the past week.
    You can see how the new 'Bed loft' is regular while 'Loft bedroom' is all over the place. It measures lower extremes and sometimes heads in the opposite direction to the other sensors.

    Thanks for your insights
    I'm calling this resolved.

  6. #6
    Automated Home Legend
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    Sounds like you had a faulty unit.

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