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Thread: Evohome - comfortable temperature

  1. #1
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    Default Evohome - comfortable temperature

    Hi All,

    I'm new to the forums and just installed my evohome system last night.

    I set the schedules up with 19 as my "comfortable" temperature and 16 as an overnight/empty room temperature. This is comparable to what we had set on the old thermostat, however that was in the hall which it turns out is probably a lot cooler than the rest of the house.

    As a result the house felt pretty cold this morning so I've adjusted the schedules to 21 for "comfortable", 18 overnight and 19 for bedrooms during the day that may be used occasionally. This feels a bit high based purely on the numbers but time will tell if this is the right temperature.

    My question is, what do you have yours set to and am I just being a softy? Did anyone else have to adjust their expectations when moving to individual room control?

    In addition, we have a gro egg thermometer in my daughters room and it seems to show a temperature circa 2 degrees lower than the Hr92 despite only being a metre apart. Which is more likely to be correct?

  2. #2
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    "Comfortable" temperature is going to depend on a lot of things, including where the temperature sensor is in the room and how accurately it is sensing the room temperature.

    21C measured/controlled by a wall mounted sensor is going to feel warmer than 21C measured by an HR92 - because the HR92 is close to the radiator and is thus sensing the heat of the radiator. This causes it to think the room is warmer than it really is, thus the true room temperature is lower than reported/scheduled as you have noticed with your gro egg comparison. (I have one of those! Although our son has outgrown it )

    How much error there will be depends on a whole host of factors like where the radiator is mounted, whether the HR92 is well exposed to the room or stuck behind furniture, whether the radiator is boxed in, whether it's an old fashioned panel or a convector, whether doors/windows etc are open to the room. To get reasonably accurate temperature sensing at the HR92 you need good convection of air around the room up past the HR92. If you don't, it could be a few degrees out.

    There is a calibrate option in the HR92 menus that allows you to apply an offset to the built in temperature sensor to attempt to correct for any error.

    I'd generally recommend setting calibrate on all HR92's to -1C to begin with and see how the actual room temperature measured by some other device away from the radiator compares to that reported by the HR92. If the room measured another way is colder than the HR92 reports then you want to set the calibrate more negative to compensate. Give it at least an hour after changing the calibrate offset for it to attempt to get the room to the new set point.

    The amount of compensation required will change with different conditions such as the seasons, so if you're really picky about the temperature being spot on in all conditions a remotely wall mounted sensor is the best option.

    Regarding children's bedroom temperatures, I ended up installing a DTS92 - which is one of the remote sensors available for Evohome in our sons room about a metre above the cot out of his reach. This is a couple of metres from the radiator and window and gives a very accurate sensing of the temperature in the vicinity of the cot and away from the radiator. After a bit of experimentation we have his room at 18C at night as sensed by this remote sensor, and he sleeps right through the night neither too hot or too cold.

    In other parts of the house I have the living room scheduled for 21C in the evenings with a wall mounted DTS92 as the sensor which is near the light switch behind the sofa some distance from the radiators, so it is sensing true room temperature.

    In other downstairs rooms including those with HR92's as the temperature sensor (calibrate set to -1C) I have them scheduled to 20C when in use, and 18C at times of the day when we are home but not really using those rooms. Dropping the temperature of unused rooms like kitchen and bathroom 2C during the day outside the times the rooms get used saves quite a bit of gas but doesn't let them get so cold that cold draughts will pass between rooms when doors are opened.

    At night we only schedule the bedrooms to be on - son's at 18C and ours at 16C as we prefer a cooler room with more covers. The rest of the house is scheduled to 5C over night and relies on optimal start to get it warmed back up again in time for people getting up. Letting the downstairs cool naturally at night then warming it up again in time for the morning uses a lot less gas than keeping it warm all night, as heat loss from a house depends on the temperature difference between inside and outside. Optimal start means you only have to specify the "be ready by" time in your schedules, and the system will work out how much earlier each zone needs to come on to achieve that, and adapt continuously as the seasons and weather change. (Automatically coming on earlier in winter and later in summer)

    If you have your downstairs night time setback only to 18C you'll find that your heating runs a lot in the night and will cost you a lot of gas. Better to let it get cold overnight then warm up in time for getting up, unless you have a habit of getting up and staying up a lot in the night.
    Last edited by DBMandrake; 17th December 2018 at 01:22 PM.

  3. #3
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    Wow, thanks DBMandrake for the very comprehensive answer! I'm using the evohome controller in the living room because the Hr92 is behind the sofa but the other rooms should have reasonable circulation. Sounds like my temperatures are about right and with the - 1 calibration would probably keep us all nice and warm without being overkill.

    Will definitely take the tip about downstairs overnight on board.

    Thanks again!

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    I have the problem that comfortable for me and comfortable for the missus are values that are several degrees apart!

    P.

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    Quote Originally Posted by paulockenden View Post
    I have the problem that comfortable for me and comfortable for the missus are values that are several degrees apart!

    P.
    I have the same problem Paul. I thought women were more able to withstand cold as well!

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    Quote Originally Posted by mjombly View Post
    I'm using the evohome controller in the living room because the Hr92 is behind the sofa but the other rooms should have reasonable circulation. Sounds like my temperatures are about right and with the - 1 calibration would probably keep us all nice and warm without being overkill.
    I probably should have mentioned, the calibrate setting on an HR92 only has an effect on HR92's that are temperature sensors for the zone. So if you had multiple HR92's in a normal "single room zone" only the first HR92 is actually a sensor, the others are slaves and their calibrate setting does nothing. (Although it doesn't hurt to set it)

    Likewise in your living room using the Evohome controller as the temperature sensor for the zone, the calibrate setting on the HR92 won't have any effect as it's not the sensor. However the Evotouch itself has a calibrate adjustment for its own built in sensor - if you look in the installer menu system settings (I think) you'll find a calibrate option that works similarly to the one on the HR92.

    Because the Evotouch generates some heat internally I find that it over-reads by about 1C compared to the true room temperature similar to HR92's. So I've calibrated my Evotouch's sensor to -1.0C after comparing it to an independent sensor hanging on the wall near the Evotouch and that seems to be about right for mine, which is wall mounted in our hallway.

    The other wall sensors like the DTS92 don't generate any internal heat and therefore seem to be spot on within 0.1C without any calibration. (I'm not sure if they even have a calibrate option!)

  7. #7
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    Living Room: 22C evening and weekends (I don't compensate HR92, so I just boost the temp up, it's really 21C on the sofa)

    Bedrooms: 1 hour prior to bed time: 19C, then 17C setback during night. 98% of the time the heat is only on that 1 hour prior to bed, and doesn't normally come on at all at night, but it has been known to come on at night during particularly cold nights.

    Hall / Kitchen: 17C morning, evening and weekends (when awake and in)

    Bathrooms: mine are uncontrolled, but if they are controlled, you'd want it 22-23C, since you're generally rather trouserless when using it.

    All rooms are set to 10C when not occupied or asleep. While it's way above frost stat temps (4-5C), I've learned that home insurers don't like heating to be below 10C.

  8. #8
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    Thanks everyone for your input. So far my wife and I are actually on the same page with the temperatures!

    The radiators in our house are column style radiators which I think are primarily radiating rather than convection so the Hr92s seem to read about 2 degrees higher than other thermometers. (at least whilst they're on!). I'll keep an eye out for some cheap dts92e units on ebay but for now I'll calibrate them down by a couple of degrees.

    That aside the system seems to be working OK except for one room that the system just can't get up to temperature (the living room with the evohome controller in). I'm wondering if the radiator is linked in series with one of the other radiators and is therefore not getting any hot water. It does seem to get hot but not constantly which I'd expect when it's 3-4 degrees below the set temperature.

    Will the system keep trying (i.e boiler on constantly) or does it eventually learn that it's futile and give up? It's showing as 100% heat demand in the installer menu and I've opened the lockshield valve as far as I can. Could just be gunked up I guess.

    Thanks again for the help, I've been researching for months and was really excited to get it up and running and then really disappointed when it didn't seem to be working properly. Think I'm back on track now!

  9. #9
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    Quote Originally Posted by mjombly View Post
    That aside the system seems to be working OK except for one room that the system just can't get up to temperature (the living room with the evohome controller in). I'm wondering if the radiator is linked in series with one of the other radiators and is therefore not getting any hot water. It does seem to get hot but not constantly which I'd expect when it's 3-4 degrees below the set temperature.

    Will the system keep trying (i.e boiler on constantly) or does it eventually learn that it's futile and give up? It's showing as 100% heat demand in the installer menu and I've opened the lockshield valve as far as I can. Could just be gunked up I guess.
    Is this a room with 2 radiators? If so, without any configuration the first radiator you bound would be the 'master' temperature sensor - in rooms with more than 1 radiator it's recommended you have a separate temp device, like a DTS92. However, given the evohome controller is in that room, you're in luck as that can be used as the temp device. Configure the zone again and when it asks do you want the controller to be the temperature device, instead of saying 'no', say 'yes'.

  10. #10
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    Hi jvallis, thanks for the suggestion but I'm actually already using the controller as the sensor in that room. It does have 2 radiators but only one with a trv valve currently so only one hr92. If anything that should make it overshoot but it can't seem to get above 18 degrees in there (as measured by the evohome controller)

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