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Thread: Hr92 position

  1. #1
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    Default Hr92 position

    Hi all,

    Any idea how these measure the temperature effectively being right next to the radiator?

    I noticed there is an elongated oval hole on the opposite side to the screen/buttons - Iím guessing this is close to where itís temperature sensor is. So what is the best way to orient the HR92? I guess it was designed to have the screen facing out, but is that the best way?

  2. #2
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    Quote Originally Posted by Meh View Post
    Hi all,

    Any idea how these measure the temperature effectively being right next to the radiator?

    I noticed there is an elongated oval hole on the opposite side to the screen/buttons - I’m guessing this is close to where it’s temperature sensor is. So what is the best way to orient the HR92? I guess it was designed to have the screen facing out, but is that the best way?
    The hole on the back you're referring to just goes into the battery compartment - there is no sensor in there.

    I've disassembled one of mine for repair twice (our 3 year old broke the screen off not once but twice, first repair attempt successful, second not!) and as far as I know the temperature sensor is just one of the chips on the main PCB, which is buried inside behind the screen. (The ribbon cable for the screen passes through a slot directly to the PCB)

    So as far as I know there is no "best" way to orient an HR92 for temperature sensing as it's just measuring the internal temperature of the device, so indirectly the case temperature. Some of mine face directly out from the wall for better visibility and some in high risk areas like the hallway face along the wall away from the radiator to minimise the chance of being knocked with the screen extended.

    One thing you can do to improve measurement accuracy is to ensure you always install them on the return side of the radiator - when the radiator is in a partial flow state this end will be significantly colder, especially the pipe work and valve body that the HR92 sits on.

    Accuracy is also greatly improved if your radiator is a convector vs an old fashioned non-convecting panel, and also if you have a side plate which are common on modern radiators - the side plate acts as a good heat shield between the radiator and HR92.

    At the end of the day though if you want true accuracy, use a remote sensor. All but three of my zones now use remote sensors and I wouldn't go back to using the HR92 as sensor in any of those zones. No amount of trickery will make up for the inherent inaccuracies of trying to measure room temperature near the floor beside a hot radiator.

  3. #3
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    The HR80 is slightly different in that respect and has a visible temperature probe that is sitting behind a grill/vent. I have found that turning that grill away from the radiator as opposed to having the screen point forward is the best position to measure room temperatures. But as @DBM says, for any rooms where true comfort is important, your only real solution is a remote sensor.

  4. #4
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    Great advice guys. Is there a small remote sensor available that doesn’t look ugly?

    For my Heatmiser downstairs there’s really small square ones not much larger than a 50p coin that I stick in hidden places on the room.

  5. #5
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    The smallest sensor is the T87RF.
    Last edited by bruce_miranda; 8th April 2020 at 03:30 PM.

  6. #6
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    Is that the same as the y87rf thermostat? I can’t find that exact code.

  7. #7
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    Quote Originally Posted by Meh View Post
    Is that the same as the y87rf thermostat? I can’t find that exact code.
    The Y87RF is the package with the T87RF and the BDR91. You don't need the BDR91.

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    Quote Originally Posted by bruce_miranda View Post
    The smallest sensor is the T87RF.
    Is it smaller than a DTS92E ?

  9. #9
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    I would say yes. The mounting screw holes are exactly the same between the two. I have swapped them on the wall, hence I know. But the surface area of the T87RF is definitely smaller than the DTS92E.

  10. #10
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    On a side note I have the current setup.


    Heatmiser thermostats for underfloor downstairs, separate Honeywell timer for hw upstairs, and a heatmiser thermostat for all heating upstairs in the landing.

    The upstairs thermostat had live, neutral and call for heat. I will replace the upstairs with evo home.

    I guess the easiest thing to do is wire the bdr91 to the boiler and leave existing wiring as is. At the heatmiser use the live and neutral to power the atf600 (wall mount panel for the controller) and terminate the call for heat on a electrical block and leave it unused.

    This way in case there’s some other wiring il missing to valves etc it should still all work.

    Sound ok?

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