Evohome Bug

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  • erik
    Automated Home Guru
    • Feb 2015
    • 244

    #16
    I can share my temperature logging results, if you want.

    This is my living room when using a simple cheap old Honeywell Round on/off thermostat. It uses TPI (10 minutes interval), but has no learning capabilities. It maintains a very constant temperature however. The radiator is constantly warm to the touch. It's doing a good job:


    And this is my living room when using Evohome. The temperature is going up and down. The radiator is very hot for 1.5 hours and then becomes very cold for over 2 hours, etc, etc. Every time the room cools down, and the radiator becomes cold, it becomes very chilly and uncomfortable:


    What might be important, like you, I was only heating 1 zone during these tests and it happened when using Evohome in single zone modus as well (no HR92's. Just Evotouch + BDR91).

    And my gas meter logger was showing pretty much the same picture by the way (the simple round thermostat uses a moderate constant amount of gas/hour, Evohome is using a high amount for 1.5 hours, then no gas for the next 2 hours, etc.). The end result for an entire day of gas usage was about the same.
    Last edited by erik; 13 October 2015, 05:52 AM.

    Comment

    • electronicsuk
      Automated Home Sr Member
      • Sep 2015
      • 55

      #17
      I must admit that your evohome log doesn't look great, but for a fair comparison they should really both be displayed on the same scale. Evohome definitely isn't regulating the temperature as well as your basic thermostat, but the graduations on the second graph are making the changes appear more pronounced than they really are. As others have mentioned, perhaps this is due to the boiler cycle time settings? This is especially true as you're only running a single zone, which is going to lead to a lot of boiler cycling if the room doesn't put much heat load on the boiler.

      Comment

      • erik
        Automated Home Guru
        • Feb 2015
        • 244

        #18
        pictures have been updated, this is the best I can do right now, scale going from 16 tot 18.5 on both.

        Can you explain further what you mean exactly with it being due to boiler cycle time settings? What settings should we change? And to what exactly? And what's your theory exactly? As far as I can tell, both the basis thermostat and Evohome use 10 minute intervals to run the same boiler and both use a minimum ON-time of about 1 minute. Difference seems to be: the basic thermostat seems to be intelligent enough to skip a 10 minute interval every now and then to keep the temperature just right.

        Or are you saying we shouldn't be using Evohome for heating just 1 zone at all (because I thought that's what zoning was for, heating just the room(s) you're using)?
        Last edited by erik; 12 October 2015, 08:02 PM.

        Comment

        • electronicsuk
          Automated Home Sr Member
          • Sep 2015
          • 55

          #19
          Originally posted by erik View Post
          Can you explain further what you mean exactly with it being due to boiler cycle time settings? What settings should we change? And to what exactly? And what's your theory exactly? As far as I can tell, both the basis thermostat and Evohome use 10 minute intervals to run the same boiler and both use a minimum ON-time of about 1 minute. Difference seems to be: the basic thermostat seems to be intelligent enough to skip a 10 minute interval every now and then to keep the temperature just right.
          Erik, I'll hold my hands up here, I've taken another look at the graphs you posted and I don't think my explanation fits with what you're seeing. Hopefully one of the Honeywell guys will be able to work this one out - they should certainly have better knowledge of the inner workings of the control logic than you or I!

          Originally posted by erik View Post
          Or are you saying we shouldn't be using Evohome for heating just 1 zone at all (because I thought that's what zoning was for, heating just the room(s) you're using)?
          My thought was that as you're only running one zone, you don't get the same level of diversity as you would if you had multiple zones on at once. With three zones on, there's a good chance that at least one of them will always be demanding heat, and so the boiler cycle rate is easily met. If you have only a single zone in use and the room has little thermal mass so is quick to heat up and cool down, evohome might be reacting in strange ways in order to obey the cycle rate. However, assuming you're using the standard 6 cycles per hour, this doesn't look to fit with the timings in your logs.

          Comment

          • Rameses
            Industry Expert
            • Nov 2014
            • 446

            #20
            Originally posted by erik View Post
            pictures have been updated, this is the best I can do right now, scale going from 16 tot 18.5 on both.

            Can you explain further what you mean exactly with it being due to boiler cycle time settings? What settings should we change? And to what exactly? And what's your theory exactly? As far as I can tell, both the basis thermostat and Evohome use 10 minute intervals to run the same boiler and both use a minimum ON-time of about 1 minute. Difference seems to be: the basic thermostat seems to be intelligent enough to skip a 10 minute interval every now and then to keep the temperature just right.

            Or are you saying we shouldn't be using Evohome for heating just 1 zone at all (because I thought that's what zoning was for, heating just the room(s) you're using)?
            Erik - Are you ok for us to share with everyone in the forum the readings and graphs we took from your home/system on 28th Feb when you raised this the first time? This might help show the forum what we measured.
            getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

            Comment

            • mikey8156
              Automated Home Jr Member
              • Dec 2011
              • 37

              #21
              Rameses, please test it with 1 radiator running on your system, thanks.

              Comment

              • erik
                Automated Home Guru
                • Feb 2015
                • 244

                #22
                Originally posted by Rameses View Post
                Erik - Are you ok for us to share with everyone in the forum the readings and graphs we took from your home/system on 28th Feb when you raised this the first time? This might help show the forum what we measured.
                I don't remember it exactly, can you share it in Private Message for me to check first please?

                Comment

                • Rameses
                  Industry Expert
                  • Nov 2014
                  • 446

                  #23
                  Originally posted by erik View Post
                  I don't remember it exactly, can you share it in Private Message for me to check first please?
                  Sure - seeing as you don't have an active account with Honeywell or live product since May I will need to ask you some security questions just to be sure you are who you say you are.
                  getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

                  Comment

                  • erik
                    Automated Home Guru
                    • Feb 2015
                    • 244

                    #24
                    your PM inbox is full, so I can't answer your PM
                    Last edited by erik; 13 October 2015, 09:19 PM.

                    Comment

                    • mikey8156
                      Automated Home Jr Member
                      • Dec 2011
                      • 37

                      #25
                      Rameses, with only 1 radiator on, have you managed to test on your system whether a demand signal is sent to the boiler when the room temperature is between 0.5C below the set point and above.

                      Comment

                      • erik
                        Automated Home Guru
                        • Feb 2015
                        • 244

                        #26
                        Originally posted by Rameses View Post
                        Sure - seeing as you don't have an active account with Honeywell or live product since May I will need to ask you some security questions just to be sure you are who you say you are.
                        Hi Rameses. I can't answer your PM, because your inbox is full.

                        Comment

                        • erik
                          Automated Home Guru
                          • Feb 2015
                          • 244

                          #27
                          Is Rameses still active? He asked me to PM him, but I can't.
                          Last edited by erik; 27 October 2015, 05:54 PM.

                          Comment

                          • mikey8156
                            Automated Home Jr Member
                            • Dec 2011
                            • 37

                            #28
                            He did not reply to me either.

                            Comment

                            • top brake
                              Automated Home Legend
                              • Feb 2015
                              • 837

                              #29
                              Is there a specific question you have, might be able to help.
                              I work for Resideo, posts are personal and my own views.

                              Comment

                              • mikey8156
                                Automated Home Jr Member
                                • Dec 2011
                                • 37

                                #30
                                When only 1 radiator is demanding heat from the boiler, no demand signal is sent until the room temperature is 0.5C below the set up. This causes the room temperature to oscillate.
                                Please can you check that you are getting a similar affect with your system, thanks.

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