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Thread: Evohome display / remote sensing questions

  1. #1
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    Default Evohome display / remote sensing questions

    Just got an Evohome setup (wifi display, boiler relay on combi boiler and 6x HR92). Generally loving it, a few questions arise after living with it for a little bit:

    1) Is there any way to have the backlight of the Wifi screen (ATC928G3000) turn off completely? I can't seem to manage it from the settings screens, despite the options seeming to imply that there are timeouts to turn it off. The room I have it in at the moment is used for projection TV, so the additional ambient light from the display ruins contrast. I'd rather not stick it in a cupboard or another room.

    2) I notice that the Wifi screen temperature readout is pretty wildly off. Usually looks to be 24-26'C on mine, varies with handling. Does this make it pointless to calibrate it? When I saw this delta vs ambient I decided to ignore this temperature in my initial setup and am only using the remote sensors in the HR92s, which leads me to:

    3) In the lounge where I have the Wifi screen the two HR92s are in poor, partially enclosed locations which in practice seems to mean the room temperature reaches optimum comfort level but then drops before their own local climate does, leading to a slight feeling of chill. To correct this I think I'd need to use a remote sensors, which I guess means either the one in the screen (assuming I can resolve 1) and 2) ) , or adding a T87RF or DTS92 (any other options?). In this situation is fiddling with the offset of the HR92 likely to be fruitless, and just result in a room which initially gets a little too warm and then drops off to the comfort temperature?

    4) Is there any reason to prefer the T87RF or DTS92, other than cost (DTS92) or arguably aesthetic design (T87RF)?

    Many thanks for any advice.

  2. #2
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    Mine goes to nearly black at a user set time, night-time mode I recall, that might help. I have mine on the minimum illumination and it looks like it's 'on' relative to most products set to minimum back-lighting.

    There can be a 3-4C temperature gradient between floor and ceiling, so the apparent reading accuracy does not surprise me. See the other discussion on HR92 Observations, we are concluding the devices are very accurate, so if it's reporting 24C then that's what it will be. Handling will affect the reading from your body.

    Using external sensors will help with your situation, but most of this is trial and error as every house and design is different and there is no one size fits all solution, although the TPI logic in the Honeywell system does a very good job, plus it takes a few weeks to learn about the environment being controlled.
    .

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    I'm really wanting a mode where the screen is totally black, with the backlight turned off, until such a point as you choose to interact with the display. Apart from anything, with this being an eco system, you'd expect to be able to turn off the backlight! I've tried the "night mode", which can be used permanently it seems, but in that mode (unless I'm mistaken) backlight is still lit, which puts out a notable glow. My projector has extremely good black levels, so this glow stands out in the room.

    I am pretty sure the local temperature reading in the ATC928G3000 is pretty far out for the ambient even a few cm away from it, and being affected by the display backlight / charging circuit etc. I'm sure I've seen other posts indicating similar.

    I am sure the HR92's are accurate and just reflecting the fact that they are boxed in with warm air trapped around them when the rest of the room is cooling quicker.

  4. #4
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    Quote Originally Posted by jimbof View Post
    Just got an Evohome setup (wifi display, boiler relay on combi boiler and 6x HR92). Generally loving it, a few questions arise after living with it for a little bit:

    1) Is there any way to have the backlight of the Wifi screen (ATC928G3000) turn off completely? I can't seem to manage it from the settings screens, despite the options seeming to imply that there are timeouts to turn it off. The room I have it in at the moment is used for projection TV, so the additional ambient light from the display ruins contrast. I'd rather not stick it in a cupboard or another room.
    You can't turn off the backlight completely no. You can set it to dim somewhat and the night mode changes the colour scheme to a dark scheme (I have mine set to switch to this automatically after 8pm) but that's all you can do. So if glare from the screen is still a problem then your only choice really is to mount it in another room. I have mine on a wall mount in the hallway partly for this reason as it does put out quite a bit of light that would be annoying in a mood lit living room.
    2) I notice that the Wifi screen temperature readout is pretty wildly off. Usually looks to be 24-26'C on mine, varies with handling. Does this make it pointless to calibrate it? When I saw this delta vs ambient I decided to ignore this temperature in my initial setup and am only using the remote sensors in the HR92s, which leads me to:
    What do you mean by the "Wifi screen temperature readout" ? Are you referring to all of the zone readings, or are you using the Wifi controller itself as the temperature sensor for your living room and finding that the reading for the living room seems unusually high ? If the latter and you are handling it often then the reason it is reading so high is hand heat! The sensor inside is quite fast acting, if you hold it in your hands for just a few minutes the reading will shoot up to about 30 degrees. This is not a fault - it's just measuring the temperature of your hands... (human skin temperature is normally about 32-33 degrees)

    It will take a while for this reading to drop down again as well. Basically you shouldn't use the evohome's built in sensor for a zone if you expect to be picking up the controller or moving it around a lot as hand heat will throw the reading completely out, and depending on where you put it down in the room it will sense the room temperature differently since different parts of the room will be at different temperatures and some parts of the room are more ideal than others as a sensing point. I have mine mounted on the optional wall mount in the hallway where the old wall stat used to be and 99.9% of the time it stays on the mount and is never hand held - because of this it works very well as a sensor.

    I've found that the calibration needs to be set to -1.0 degrees (in system setup) for it to agree accurately with a reference thermometer, probably due to a small amount of internal heat generation, however once it has been calibrated it seems pretty accurate as long as I don't handle it. (Pressing the screen with you fingers is fine, it's holding the casing that heats it up)

    3) In the lounge where I have the Wifi screen the two HR92s are in poor, partially enclosed locations which in practice seems to mean the room temperature reaches optimum comfort level but then drops before their own local climate does, leading to a slight feeling of chill. To correct this I think I'd need to use a remote sensors, which I guess means either the one in the screen (assuming I can resolve 1) and 2) ) , or adding a T87RF or DTS92 (any other options?). In this situation is fiddling with the offset of the HR92 likely to be fruitless, and just result in a room which initially gets a little too warm and then drops off to the comfort temperature?
    If the HR92's are in poor locations such as a corner, obscured by objects etc then adjusting the calibrate setting is likely to be fruitless and a remote sensor is probably warranted. Although calibrate would fix an offset in some conditions when conditions changed (like much warmer or colder weather) the required offset would change as well, so it would never be quite right.

    Because you've already said that you don't like the glare from the wifi controller in your living room and it would probably need to be wall mounted and not handled to give good readings that leaves other sensors like T87RF and DTS92.

    I'm a big fan of a remote sensor from the point of view of accurate temperature control and I've talked about the reasons why at length in other threads, but suffice to say as long as it is located in a suitable location in the room then its a far more accurate way to measure the room temperature than trying t use an HR92's built in sensor, and it doesn't matter whether your HR92's are in a favourable location or not, they now only have to control the radiator valve. I have a DTS92 in my Living room and another one in the Bedroom.

    Ideal placement for a remote sensor would be:

    1) On a wall 1.2 metres above the floor.
    2) At least 1.5m from the nearest radiator
    3) Not mounted on an outside wall or under a window
    4) Not mounted near a source of heat such as a TV
    5) Not mounted where daytime sun can shine directly on the sensor
    6) Not mounted too close to a doorway
    7) Ideally mounted in a part of the room near the occupants, such as near the sofa in a living room.

    Meeting all of the above at once in a typical small British living room can be a major challenge, I had to compromise with the doorway - I found after experimentation that beside the light switch at the door (right next to the main sofa) was actually the best place for it to be even though its only 30cm from the door. It meets all the other requirements.

    Temperature regulation of the room was already good with the HR92 but I found I had to turn it up manually in really cold weather, with the remote sensor I find I don't have to make any manual corrections - whether its mild outside or freezing the room is spot on at a comfortable temperature. It has also reduced the amount of time that it takes the room to get up to temperature. (As the HR92 sensor tends to think the room is up to temperature before it really is and throttles the radiator back even though further parts of the room can still be quite cold)
    4) Is there any reason to prefer the T87RF or DTS92, other than cost (DTS92) or arguably aesthetic design (T87RF)?
    The T87RF is more aesthetically pleasing but the DTS92 is more functional and cheaper. So it's a choice between aesthetics and functionality/cost.

    I haven't used a T87RF but it is fairly limited in what it can do - you can turn the casing to adjust the temperature and that's about it. You can't lock the adjustment like you can with the HR92 or DTS92 so if you have small children that like to fiddle this could be a problem as you can't prevent them adjusting it.

    The DTS92 has a quick "off" button that sets the zone to 5 degrees and an economy button that applies a pre-configured set back temperature for a certain amount of time, and as above you can lock it for temperature changes remotely from the controller.

    Your other choices are the HCF82 which is a sensor only with no controls or readout at all, or the HCW82 which looks similar but has an analogue dial. Both of these I think are pretty ugly though.
    Last edited by DBMandrake; 2nd December 2016 at 12:41 PM.

  5. #5
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    Quote Originally Posted by jimbof View Post
    I am pretty sure the local temperature reading in the ATC928G3000 is pretty far out for the ambient even a few cm away from it, and being affected by the display backlight / charging circuit etc. I'm sure I've seen other posts indicating similar.
    As mentioned above - I've found the offset required is only about -1 degrees. However that is with it mounted on the wall which means it will get proper convection currents. I notice for example if I lie it on a sofa the reading will be 2-3 degrees above ambient, probably due to internal heat building up due to the insulation of the sofa material, and the lack of convection current through the vents when its lying on its back on a sofa instead of vertically mounted on the wall.
    I am sure the HR92's are accurate and just reflecting the fact that they are boxed in with warm air trapped around them when the rest of the room is cooling quicker.
    The sensor itself in the HR92 is very accurate, (better than 0.1 degrees probably) but it can only very accurately measure the temperature beside the radiator. In some rooms this can be a very poor representation of what the temperature is out in the room away from the radiator, so in this sense it can be very inaccurate. This is where a remote wall mounted sensor can help.

    I've found my DTS92 agrees with the actual room temperature measured by another thermostat within about 0.1 degrees - and without having to apply any calibration offsets. This is probably due to the DTS92 not having any significant internal heat sources like the controller does to skew the reading.

  6. #6
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    Thanks for the very extensive reply, much appreciated.
    Quote Originally Posted by DBMandrake View Post
    You can't turn off the backlight completely no... I have mine on a wall mount in the hallway partly for this reason as it does put out quite a bit of light that would be annoying in a mood lit living room.
    Yes, I have Rako lighting and when projecting a very small amount of light in the room. In all cases the light from the screen is bothersome (quite a cheap screen which does bleed quite a bit - not complaining tho because I think the whole kit is brilliant value).
    Quote Originally Posted by DBMandrake View Post
    What do you mean by the "Wifi screen temperature readout" ?
    I mean the internal sensor. I'm not using it for sensing purposes because the reading seems high. In my room at the moment it is on the table top stand, in a corner, that is located under a small speaker. I think that it is probably self-heating the local environment it is in, if it does work reasonably well in a wall-mounted situation (I'll have to experiment). but regardless, if I can't turn off the screen it useless to me as a temp sensor as the only room I need a wall sensor for is the room I don't want the light in! . I'll probably stick it in the cupboard and just get it out when I want to adjust something (not very often it seems, 3 days in and I already think it works brilliantly).
    Quote Originally Posted by DBMandrake View Post
    If the HR92's are in poor locations such as a corner, obscured by objects etc then adjusting the calibrate setting is likely to be fruitless and a remote sensor is probably warranted. Although calibrate would fix an offset in some conditions when conditions changed (like much warmer or colder weather) the required offset would change as well, so it would never be quite right.
    That is what I figure; hence I'd rather just do it right now and have a setup which works all the time, rather than faffing around with offsets which will inevitably need to change. Thanks for all the really detailed info on the sensors, I'll probably go for the DTS92 in that case.

  7. #7
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    So it does look like if I leave the Evohome controller alone on the stand it just needs a 1.5 degree offset dialing in, which achieves more comfort than relying on the HR92s in their poor location. The light is more of an issue, so I'm probably going to end up using the DTS92 I just picked up (63 on ebay with the relay box). Any ideas for an innovative use for a spare relay box?!

    It really is a shame that the display backlight can't be turned all the way off, as it is a box I could have done without having to buy. One for the Wishlist I guess.

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    Quote Originally Posted by DBMandrake View Post
    You can't lock the adjustment like you can with the HR92 or DTS92 so if you have small children that like to fiddle this could be a problem as you can't prevent them adjusting it.
    I didn't realise you could lock the DTS92 other than preventing a local override on the zone. We had the lounge up to 25C before we realised little fingers had be fiddling. How do you lock it?

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    It really is a shame that the display backlight can't be turned all the way off, as it is a box I could have done without having to buy.
    A piece of card taped along the top of the controller makes a really simple flip-up cover to block out the backlight. Or if you want to spend a bit more time, as the controller has a resistive touchscreen you could try some window tint film or other coloured film to reduce the glare from the backlight when it's set to minimum brightness and then set it to maximum brightness for daytime usage. I agree though, it would be far more preferable if the backlight simply had an off option.

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    Quote Originally Posted by guyank View Post
    I didn't realise you could lock the DTS92 other than preventing a local override on the zone. We had the lounge up to 25C before we realised little fingers had be fiddling. How do you lock it?
    Sorry for the confusion - I'm talking about disabling local override for the zone in the controller configuration - the same way that you do to disable the controls on an HR92.

    On a DTS92 in a zone with local override disabled as soon as you try to press any button it displays an icon of a key and does not let you make any adjustments. A T87RF ignores the local override disable setting of the zone and still lets you make adjustments to the set point - that's the difference. As far as I know there is no way to lock a T87RF against set point adjustments by fiddly fingers, although it's possible they're less likely to figure out how to do it since it doesn't use buttons!
    Last edited by DBMandrake; 7th December 2016 at 10:04 AM.

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