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Thread: Evohome Single Zone Not Working

  1. #21
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    Ok probably should have read that properly.. assuming you got 30 degrees but turning the dial on the HR92.. then does sound like a bug.

  2. #22
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    Quote Originally Posted by Stevedh View Post
    Depends... what target temperature is showing in the HR92?
    Um... 30 degrees.... but in any event why would that matter given the fact the controller knows the target temp, and that it's the controller that decides on heat demand for the boiler NOT the TRV? It's possible the TRV sets its position based on its idea of target temp, and that it then reports its idea of heat demand back to the controller, but as a design principle that wouldn't make much sense. It's far more likely the controller tells the TRV what position it should be in. But anyway, as I say, the TRV's showing the correct target so it's all pretty moot.

    As a further test, I used the TRV to turn the zone off... the controller reported 0% demand, so at least it got that right... the TRV also closed, so that bit worked. I then turned the temp up to 35 degrees on the TRV. The valve opened - by the sound of it quite a way ( if not 100%, obviously I've no real way of knowing how far, but the motor ran for a good few seconds. ) Controller now shows 35 degrees target. Heat demand for the zone is........... 4%.

    Edit: I've opened a case with Honeywell. I'm sure I'll get the normal dumb standard responses you tend to get from support desks but I'll update the thread if I get anywhere sensible.
    Last edited by sidepipe; 9th November 2018 at 12:52 PM.

  3. #23

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    Quote Originally Posted by sidepipe View Post
    Um... 30 degrees.... but in any event why would that matter given the fact the controller knows the target temp, and that it's the controller that decides on heat demand for the boiler NOT the TRV? It's possible the TRV sets its position based on its idea of target temp, and that it then reports its idea of heat demand back to the controller, but as a design principle that wouldn't make much sense. It's far more likely the controller tells the TRV what position it should be in. But anyway, as I say, the TRV's showing the correct target so it's all pretty moot.

    As a further test, I used the TRV to turn the zone off... the controller reported 0% demand, so at least it got that right... the TRV also closed, so that bit worked. I then turned the temp up to 35 degrees on the TRV. The valve opened - by the sound of it quite a way ( if not 100%, obviously I've no real way of knowing how far, but the motor ran for a good few seconds. ) Controller now shows 35 degrees target. Heat demand for the zone is........... 4%.

    Edit: I've opened a case with Honeywell. I'm sure I'll get the normal dumb standard responses you tend to get from support desks but I'll update the thread if I get anywhere sensible.
    The Radiator Controller actually does all the control locally, and has to report back its demand to the touchscreen, which in turn collates demands from all zones and sends this on to the boiler controlller.

    The Radiator Controller only syncs with the touchscreen roughly once every 5 minutes, so you need to leave enough time for all the messages to pass through the system. So making a setpoint change from a room sensor or touchscreen unit can take upto 5 minutes before it gets picked up at the Radiator Controller, then you have to wait for the Radiator Controller to react and pass itís demand back to the touchscreen before it signals the BDR to react. The system has worked this way for more than 15 years, and the devices need to maintain backward compatibility with these legacy devices, so I doubt it will change any time soon.

    So maybe you simply need to give the system time to react to your changes?
    Sensible Heat
    SensibleHeat.co.uk

  4. #24
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    Quote Originally Posted by SensibleHeatUK View Post
    The Radiator Controller actually does all the control locally, and has to report back its demand to the touchscreen, which in turn collates demands from all zones and sends this on to the boiler controlller.

    The Radiator Controller only syncs with the touchscreen roughly once every 5 minutes, so you need to leave enough time for all the messages to pass through the system. So making a setpoint change from a room sensor or touchscreen unit can take upto 5 minutes before it gets picked up at the Radiator Controller, then you have to wait for the Radiator Controller to react and pass it’s demand back to the touchscreen before it signals the BDR to react. The system has worked this way for more than 15 years, and the devices need to maintain backward compatibility with these legacy devices, so I doubt it will change any time soon.

    So maybe you simply need to give the system time to react to your changes?
    Nope, left it for ages. However, if the TRV actually does control things locally, then it could be the TRV not telling the controller its demand.

    Thing is ( and I'm not doubting what you say as such because you sound like you know what you're talking about, I'm just curious, ) that doesn't make a lot of sense for a number of reasons. Chiefly, if the HR92 isn't also acting as the temperature sensor as in this case, how would it even KNOW what it's demand should be, without being told by the controller? The TRV and radiator could be covered by a blanket and think the room's 30 degrees....... IF the control is all local, that would just mean having an external sensor is useless, surely?

  5. #25
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    Interesting point I'd be interested in knowing the answer on how the HR92 works when paired with an external temperature sensor.
    My guess for consistency is that the controller receives the temperature from the sensor then passes it on to the HR92 when then deciders whether or not to demand heat..hmm

  6. #26

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    Quote Originally Posted by sidepipe View Post
    Nope, left it for ages. However, if the TRV actually does control things locally, then it could be the TRV not telling the controller its demand.

    Thing is ( and I'm not doubting what you say as such because you sound like you know what you're talking about, I'm just curious, ) that doesn't make a lot of sense for a number of reasons. Chiefly, if the HR92 isn't also acting as the temperature sensor as in this case, how would it even KNOW what it's demand should be, without being told by the controller? The TRV and radiator could be covered by a blanket and think the room's 30 degrees....... IF the control is all local, that would just mean having an external sensor is useless, surely?
    The remote sensor sends its value to the touchscreen, and it in turn sends this value to the Radiator Controller (all comms go via the main unit in this case). So the Tadiator Controller receives updates around once every 5 mins from the controller. This is as much about extending battery life as anything else, only powering the radio transceiver for short periods every few minutes. Note that if you make a change at the Radiator Controller this can be sent immediately, it is only the receiving of messages by the Radiator Controller that is subject to the 5 minute polling interval.
    Sensible Heat
    SensibleHeat.co.uk

  7. #27
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    Quote Originally Posted by SensibleHeatUK View Post
    The Radiator Controller actually does all the control locally, and has to report back its demand to the touchscreen, which in turn collates demands from all zones and sends this on to the boiler controlller.

    The Radiator Controller only syncs with the touchscreen roughly once every 5 minutes, so you need to leave enough time for all the messages to pass through the system. So making a setpoint change from a room sensor or touchscreen unit can take upto 5 minutes before it gets picked up at the Radiator Controller, then you have to wait for the Radiator Controller to react and pass it’s demand back to the touchscreen before it signals the BDR to react. The system has worked this way for more than 15 years, and the devices need to maintain backward compatibility with these legacy devices, so I doubt it will change any time soon.

    So maybe you simply need to give the system time to react to your changes?
    Quoting SensibleHeatUK again because I may have discovered something and it's their reply that pointed me at it....

    I think the key was that the radiator valve tells the controller what its demand is... My guess is it's a little more complex than you said, as in the HR92 can receive information from the controller which it will use in addition to or instead of its own temperature sensor, so the controller tells the HR92 the zone temperature and it then uses THAT info to decide how open the valve should be. The HR92 then reports its position back to the controller. I don't KNOW this to be the case, but based on your info, observations, and a bit of logic, that would seem to be sensible. ( edit: I see you followed up saying as much... )

    So, with that in mind, I got to thinking it was probably the HR92 not reporting the position correctly, or something similar. I disconnected the HR92, unscrewed the base from the TRV, and did a few experiments. Long story short, I now think the base is pushing the TRV pin some way down even when it's fully open, because it screws a long way down onto the TRV body. I tightened the HR92 base only until I could feel resistance from the pin, replaced the HR92 on its base, and voila - it now works.

    I assume I missed something in the installer guide about this? ( Though to be fair to me it wasn't obvious - the additional pressure when screwing the base on was only slight. ) Surely there should've been some sort of error from the HR92 given that it knew it couldn't open fully?

    The HR92 is now very loose on the TRV body, which doesn't seem right and will be prone to move in future I'd think - is this normal or is it just a quirk of this valve?

    Anyway - hopefully problem at least worked around.... it's worth anyone else who's had similar issues double checking how the HR92 sits on the valve!
    Last edited by sidepipe; 9th November 2018 at 01:48 PM.

  8. #28
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    Quote Originally Posted by sidepipe View Post
    Quoting SensibleHeatUK again because I may have discovered something and it's their reply that pointed me at it....

    I think the key was that the radiator valve tells the controller what its demand is... My guess is it's a little more complex than you said, as in the HR92 can receive information from the controller which it will use in addition to or instead of its own temperature sensor, so the controller tells the HR92 the zone temperature and it then uses THAT info to decide how open the valve should be. The HR92 then reports its position back to the controller. I don't KNOW this to be the case, but based on your info, observations, and a bit of logic, that would seem to be sensible. ( edit: I see you followed up saying as much... )
    Sensible Heat's description of how it works is accurate, but here's a little more detail.

    Processing of temperature measurements works like this:

    Multi-room zone - every HR92 in the zone uses its own internal temperature sensor reading directly and adjusts its own radiator valve pin position to attempt to regulate the room to the target set point as measured at that HR92. The "primary" HR92 for the zone (the one you bind first) sends its measured temperature to the controller, but this is for display/informational purposes only. The temperature measurement of the other HR92's in the zone can only be seen on their own displays. Each HR92 in the zone also sends a heat demand to the controller which is based on the valve pin position, but it is a non-linear mapping that looks like the graph in the following post:

    https://www.automatedhome.co.uk/vbul...ll=1#post38185

    The controller takes the highest heat demand figure of all the HR92's within the zone and displays that as the heat demand for the zone in the diagnostics page. The highest heat demand of any zone is then forwarded onto the BDR91 or OpenTherm bridge to fire the boiler.

    Single-room zone - similar to the above but with the following differences:

    Only one temperature sensor for the zone. This could be an HR92 or a wall stat like a DTS92. In the case of an HR92 it's the first HR92 bound to the zone. Whatever the nominated sensor is, this sends the temperature reading to the controller which displays it, and also forwards it on to all HR92's in the zone every 4 minutes or so. As before, each HR92 makes adjustments to its own radiator to try to meet the set point and then sends heat demands back to the controller, which uses the highest heat demand of all the HR92's in the zone as described earlier.

    There's a couple of quirks in single room zones which aren't immediately apparent. The first is that if you have a single room zone with a single HR92 in it which is also the temperature sensor - the most common situation, the HR92 doesn't actually use it's temperature sensor reading directly. (!) It periodically sends the measured temperature to the controller (frequency of updates depends on the rate of change of temperature) which then about every 4 minutes sends it back to the HR92. The HR92 only acts on this delayed, "re-transmitted" temperature reading coming back from the controller.

    This can be proven by noting that if you rapidly heat or cool an HR92, the reading will change on the controller many minutes before the reading will change on the HR92, so that the reading on the HR92 always lags significantly behind even though it is the source of the temperature reading. Or that if you take the batteries out of the controller the temperature reading on the HR92 won't react to temperature changes at all until it eventually defaults back to standalone fallback mode. (Which takes about an hour)

    The other quirk is that even if you use a remote sensor like a DTS92 for the zone, each HR92 still uses its built in sensor for the window open detection feature, and every HR92 in a zone has its own independent open window detection. (Something to keep in mind)

    So, with that in mind, I got to thinking it was probably the HR92 not reporting the position correctly, or something similar. I disconnected the HR92, unscrewed the base from the TRV, and did a few experiments. Long story short, I now think the base is pushing the TRV pin some way down even when it's fully open, because it screws a long way down onto the TRV body. I tightened the HR92 base only until I could feel resistance from the pin, replaced the HR92 on its base, and voila - it now works.

    I assume I missed something in the installer guide about this? ( Though to be fair to me it wasn't obvious - the additional pressure when screwing the base on was only slight. ) Surely there should've been some sort of error from the HR92 given that it knew it couldn't open fully?

    The HR92 is now very loose on the TRV body, which doesn't seem right and will be prone to move in future I'd think - is this normal or is it just a quirk of this valve?

    Anyway - hopefully problem at least worked around.... it's worth anyone else who's had similar issues double checking how the HR92 sits on the valve!
    What you describe is not normal, you should be screwing the base fully onto the valve body after first turning the black wheel anti-clockwise - if you can't without it causing the valve body pin to be pushed down significantly, the valve body is not dimensionally compatible with the HR92 and will not work very well. You certainly don't want to be leaving it unscrewed as you have.

    What kind of valve bodies do you have and do they directly fit the M30x1.5 base or are you using an adaptor ?

    You might want to read the following thread where I had problems with even Honeywell's own Valencia valves compressing the pin just by screwing the base on:

    https://www.automatedhome.co.uk/vbul...encia-problems

    I eventually worked around it by using Stroke 1 mode.
    Last edited by DBMandrake; 9th November 2018 at 07:19 PM.

  9. #29
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    Quote Originally Posted by DBMandrake View Post
    What you describe is not normal, you should be screwing the base fully onto the valve body after first turning the black wheel anti-clockwise - if you can't without it causing the valve body pin to be pushed down significantly, the valve body is not dimensionally compatible with the HR92 and will not work very well. You certainly don't want to be leaving it unscrewed as you have.

    What kind of valve bodies do you have and do they directly fit the M30x1.5 base or are you using an adaptor ?

    You might want to read the following thread where I had problems with even Honeywell's own Valencia valves compressing the pin just by screwing the base on:

    https://www.automatedhome.co.uk/vbul...encia-problems

    I eventually worked around it by using Stroke 1 mode.
    Not sure what make the valve body is to be honest, but the HR92 base fits directly without an adaptor. Thing is, it does seem to work perfectly how it is now as far as I can tell.... I'd thought of using some shims of some sort but would be lucky to find some that are a perfect fit. Another option would be a blob of superglue or something just to stop it from turning.

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