Evohome Controller - Thermostat sensitivity

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  • yiangosliv
    Automated Home Jr Member
    • Dec 2015
    • 36

    Evohome Controller - Thermostat sensitivity

    Hi. I was wondering how reliable is the thermostat of the Evohome controller device. I am currently using it at 24 C (I am not using any HR92) for my single home zone. The room/house temperature seems to get the target temp and the controller instructs the valve to go off. From my past experience in other homes with central heating I can easily sense that even in other homes the target temp was 21 C those homes were warmer than mine at 24!. Any idea what might be the problem? I am thinking of buying a cheap room thermometer so i can benchmark the Evohome controller. Any ideas?
  • Fursty Ferret
    Automated Home Sr Member
    • Oct 2014
    • 84

    #2
    You can adjust the offset IIRC - my controller sits in the hall and controls it to a noticeably lower temperature than the living room even though both are set the same.

    Comment

    • DBMandrake
      Automated Home Legend
      • Sep 2014
      • 2361

      #3
      My evotouch also measures the hallway temperature, wall mounted.

      I found I had to set the controller offset to -1.0 degrees on mine so that it matched my "reference thermometer" placed directly above it on the wall, but once I did that I have found it very accurate and it agrees very closely with the other thermometer, and it also responds to changes a lot quicker. (So you need to give time for both to settle before comparing them)

      Unless you have measured the room temperature using a known good thermometer near the evotouch, I would not be so sure that the temperature setting in the "other homes" that you are anecdotally comparing to are accurate! The old wall thermostat (an old analogue mechanical stat) that we replaced with the evotouch actually regulated to a temperature of 20 degrees when you set the knob to 15 degrees...

      It also goes without saying that the placement of any wall stat (including the evotouch) is critical to the accuracy of the measurement, especially somewhere like a hallway where there are many doors to possibly colder rooms. It should also be at least 1.5 metres from the nearest radiator.

      Another thing to consider is that a single thermostat in one location in a house is never going to give a consistent/even temperature control around the whole house, that is the whole point of a zoned system like the evotouch with HR92's on each radiator to zone the house.

      Even if you want the same temperature in every room, a zoned system is the way to achieve that as it can compensate for the different thermal characteristics of each room in a way that a single central wall stat cannot. I don't really see the point of using an Evotouch in the "single zone" mode - all you really gain from it is more accurate control of the temperature in that one room and the scheduling and remote control features, but you don't get the zoning, which is the main point of the system IMHO. At most, single zone mode should be a temporary stepping stone towards a fully zoned system with HR92's.
      Last edited by DBMandrake; 5 January 2016, 11:19 AM.

      Comment

      • yiangosliv
        Automated Home Jr Member
        • Dec 2015
        • 36

        #4
        Hi All thank you for your responses. I did bought some independent thermometer so I may adjust the Generic House Temperature. my HR92s are on the way (delayed delivery) thus I suppose I will have a better control and readings on the temperature soon

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #5
          Originally posted by yiangosliv View Post
          Hi All thank you for your responses. I did bought some independent thermometer so I may adjust the Generic House Temperature. my HR92s are on the way (delayed delivery) thus I suppose I will have a better control and readings on the temperature soon
          I already had a small portable "weather station" receiver unit that does inside temp and humidity, outside temp, air pressure and so on, and for better or worse I use that as my reference around the house when comparing to the evohome temperature readings.

          I've also found with the HR92 that I have to set their calibration to -1 degree to agree with a thermometer placed out in a room. This makes the HR92 indicate 1 degree less than it otherwise would have. This makes sense when you consider that it is trying to measure the room temperature right next to the radiator, so the temperature that it measures is higher than the real room temperature by about 1 degree when the radiator is hot.

          The offset required depends on how hot the radiator is and how good the airflow is on the floor near the radiator. In theory when the radiator is warm it creates an updraft which pulls the colder air from the middle of the room towards the HR92 and up past it to minimise the influence of the local heat source (the side of the radiator) on the reading, but it will still typically be out by about a degree until calibrated. If your radiator valves are at the bottom of the radiator it will be more accurate than if they are at the top.

          If the HR92 is covered by a curtain, radiator enclosure or the floor area around it is obscured, or you just want the most accurate temperature control possible, a remote wall stat like a DTS92 will give more accurate results and is not influenced by the localised heating of the radiator at all as long as its at least about 1.5 metres away.
          Last edited by DBMandrake; 5 January 2016, 04:30 PM.

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