Thinking of adding the hot water kit to my Evohome

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  • The EVOHOME Shop
    Site Sponsor
    • Dec 2014
    • 483

    #31
    Originally posted by G4RHL View Post
    Just seen the answer elsewhere in the forum. Having read it I don't need to balance, all my radiators seem to warm up at the same time and the lock valves are all fully open.
    Not trying to take this post off topic, but if the lockshield valve is fully open on all radaitors, then the radiator(s) are not balanced (or optimised) to achieve the correct temperature drop across the radiator/heating system and your boiler will be prone to short cycling. Magic temperature numbers - 11 degree drop across the radiators/circuit for standard efficiency boilers, 20 degree drop for condensing boilers...

    System balancing is important with or without evohome.

    Comment

    • jonstatt
      Automated Home Guru
      • Feb 2015
      • 111

      #32
      Originally posted by The EVOHOME Shop View Post
      Not trying to take this post off topic, but if the lockshield valve is fully open on all radaitors, then the radiator(s) are not balanced (or optimised) to achieve the correct temperature drop across the radiator/heating system and your boiler will be prone to short cycling. Magic temperature numbers - 11 degree drop across the radiators/circuit for standard efficiency boilers, 20 degree drop for condensing boilers...

      System balancing is important with or without evohome.
      I'm glad you posted. Sorry I only got a couple of parts of my system from you. I didn't find you until after I had already purchased the rest.

      In my house, clearly no attempt has ever been made to balance the radiators. I guess that is not very surprising though. I will need to invest some time to do this. I have a good quality infrared temperature measuring device (laser pointer, point and shoot). If I aim it at the pipes at each side is that accurate enough? Or do I need something like

      Comment

      • G4RHL
        Automated Home Legend
        • Jan 2015
        • 1580

        #33
        Originally posted by The EVOHOME Shop View Post
        Not trying to take this post off topic, but if the lockshield valve is fully open on all radaitors, then the radiator(s) are not balanced (or optimised) to achieve the correct temperature drop across the radiator/heating system and your boiler will be prone to short cycling. Magic temperature numbers - 11 degree drop across the radiators/circuit for standard efficiency boilers, 20 degree drop for condensing boilers...

        System balancing is important with or without evohome.
        But having read the article about balancing it is something I would find almost impossible to do as their is no radiator that appears to heat up any quicker than any other. Presumably there is specialist equipment that will sense the temperature rising differentials of the radiators but without such I just cannot tell which heats up first, they all appear to. Perhaps the builder did balance after all 17 years ago! I guess I better check the setting of each lock valve.

        Comment

        • HenGus
          Automated Home Legend
          • May 2014
          • 1001

          #34
          Isn't this all getting a bit silly given that the perceived advantage of zoning is that rooms not in use should be kept at a low temperature. I have always had a radiator that was slow to heat up prior to the installation of Evohome. Now, thanks to my Evohome schedule, it is in the second zone to come on in the morning. My bedroom/en-suite are at target temperature at 7.10am (the boiler come on at 06.55am this morning to achieve this), and the kitchen (comprising 3 radiators) was set to achieve the required target temperature at 7.30am. When I got up to make my good lady a cup of tea at 7.15 am, all 3 kitchen radiators were nicely hot and doing their thing. I am not sure what the benefit of spending £55 would be apart from giving me something to do for a day.

          Comment

          • jonstatt
            Automated Home Guru
            • Feb 2015
            • 111

            #35
            Originally posted by HenGus View Post
            Isn't this all getting a bit silly given that the perceived advantage of zoning is that rooms not in use should be kept at a low temperature. I have always had a radiator that was slow to heat up prior to the installation of Evohome. Now, thanks to my Evohome schedule, it is in the second zone to come on in the morning. My bedroom/en-suite are at target temperature at 7.10am (the boiler come on at 06.55am this morning to achieve this), and the kitchen (comprising 3 radiators) was set to achieve the required target temperature at 7.30am. When I got up to make my good lady a cup of tea at 7.15 am, all 3 kitchen radiators were nicely hot and doing their thing. I am not sure what the benefit of spending £55 would be apart from giving me something to do for a day.
            Possibly. Like G4RHL, my radiators all seem to heat up evenly anyway. I am curious about short cycling. My boiler, the Potteron Suprima 60L has always ultra short cycled anyway. I think it maybe by design. For example, if just the hot water is on, it heats up the loop quite quickly...boiler cuts out because it has reached its temperature.....pump over-runs for 2 minutes, then it fires up again, sometimes for as short as 60 seconds and cuts out again...and this repeats over and over. It seems the differential on the boiler thermostat is very short so I went and compared it with a neighbour and it's exactly the same. Having said that the boiler is almost 9 years old now and has never faulted once (yet, touches wood rapidly)

            Comment

            • HenGus
              Automated Home Legend
              • May 2014
              • 1001

              #36
              Originally posted by jonstatt View Post
              Possibly. Like G4RHL, my radiators all seem to heat up evenly anyway. I am curious about short cycling. My boiler, the Potteron Suprima 60L has always ultra short cycled anyway. I think it maybe by design. For example, if just the hot water is on, it heats up the loop quite quickly...boiler cuts out because it has reached its temperature.....pump over-runs for 2 minutes, then it fires up again, sometimes for as short as 60 seconds and cuts out again...and this repeats over and over. It seems the differential on the boiler thermostat is very short so I went and compared it with a neighbour and it's exactly the same. Having said that the boiler is almost 9 years old now and has never faulted once (yet, touches wood rapidly)
              Actually, with my unvented HW system and system boiler, I have found that short-cycling has reduced because of the ability to set a max temp and differential. I have 60C max and 7C differential (the latter is partly due to my old thermostatic shower). The water heats up and nothing happens again until it drops to 53C. Prior to Evohome, the boiler would run just to maintain a 60C temp in the HW cylinder.

              Comment

              • jonstatt
                Automated Home Guru
                • Feb 2015
                • 111

                #37
                Originally posted by HenGus View Post
                Actually, with my unvented HW system and system boiler, I have found that short-cycling has reduced because of the ability to set a max temp and differential. I have 60C max and 7C differential (the latter is partly due to my old thermostatic shower). The water heats up and nothing happens again until it drops to 53C. Prior to Evohome, the boiler would run just to maintain a 60C temp in the HW cylinder.
                That's the differential in terms of the hot water thermostat, and I also have it set for 7 degrees right now as well. For sure this will help reduce some of the short cycling. But I am talking about the differential in the boiler thermostat, In my case the Potterton Suprima. The boiler heats the water loop that enters and leaves the hot water tank. Once it has reached the set boiler temperature (on the Suprima it is a knob with no range or number indications whatsoever!), it cuts out, as it should....but it only takes a tiny drop for it to fire up again which then sees it reach its target in 60 seconds, so it's a very very short cycle indeed. It seems the differential in the boiler thermostat itself is very very shallow on the Suprima.

                Comment

                • top brake
                  Automated Home Legend
                  • Feb 2015
                  • 837

                  #38
                  Originally posted by jonstatt View Post
                  That's the differential in terms of the hot water thermostat, and I also have it set for 7 degrees right now as well. For sure this will help reduce some of the short cycling. But I am talking about the differential in the boiler thermostat, In my case the Potterton Suprima. The boiler heats the water loop that enters and leaves the hot water tank. Once it has reached the set boiler temperature (on the Suprima it is a knob with no range or number indications whatsoever!), it cuts out, as it should....but it only takes a tiny drop for it to fire up again which then sees it reach its target in 60 seconds, so it's a very very short cycle indeed. It seems the differential in the boiler thermostat itself is very very shallow on the Suprima.
                  Short cycling could also be the boiler hitting its internal overheat stat.

                  Smart thermostats as can never work miracles on a poorly sized, poorly commissioned and nonbalanced system.

                  A heating system is like a receipe, you can all the best ingredients but if the cook isn't following the receipe it will taste and look wrong.
                  I work for Resideo, posts are personal and my own views.

                  Comment

                  • erik
                    Automated Home Guru
                    • Feb 2015
                    • 244

                    #39
                    -never mind-
                    Last edited by erik; 28 February 2015, 10:32 PM.

                    Comment

                    • jonstatt
                      Automated Home Guru
                      • Feb 2015
                      • 111

                      #40
                      Originally posted by top brake View Post
                      Short cycling could also be the boiler hitting its internal overheat stat.

                      Smart thermostats as can never work miracles on a poorly sized, poorly commissioned and nonbalanced system.

                      A heating system is like a receipe, you can all the best ingredients but if the cook isn't following the receipe it will taste and look wrong.

                      I can tell when it is the overheat stat because the boiler LED will flash red so it isn't that. But you are right about poorly commissioned. Can you believe when I moved in, I found out after about 10 months that no inhibitor chemicals had been added to the water and as a result the heat exchanger needed replacing on the boiler....not at my cost I hasten to add.
                      Last edited by jonstatt; 28 February 2015, 10:58 PM.

                      Comment

                      • erik
                        Automated Home Guru
                        • Feb 2015
                        • 244

                        #41
                        How could any boiler be properly sized when using Evohome? Boilers are sized so that they're able to heat the ENTIRE house when it's -20 outside. So when it's +5 outside and you're only heating 1 room, virtually EVERY boiler is going to be hugely over-sized. However, this should not matter. The thermostat should be able to turn on/off the boiler to achieve the desired temperature anyway.

                        Comment

                        • SimonW500
                          Automated Home Jr Member
                          • Feb 2015
                          • 21

                          #42
                          Originally posted by jonstatt View Post
                          I am curious about short cycling. My boiler, the Potteron Suprima 60L has always ultra short cycled anyway. I think it maybe by design. For example, if just the hot water is on, it heats up the loop quite quickly...boiler cuts out because it has reached its temperature.....pump over-runs for 2 minutes, then it fires up again, sometimes for as short as 60 seconds and cuts out again...and this repeats over and over. It seems the differential on the boiler thermostat is very short so I went and compared it with a neighbour and it's exactly the same. Having said that the boiler is almost 9 years old now and has never faulted once (yet, touches wood rapidly)
                          Short comment to say: exactly the same boiler.. exactly the same ultra short cycling experience.. once up to heat (and more common when either just HW or single/few TRV calling for heat) can be as short as 60 seconds firing / 2 min pump overrun / repeat. I've had my Evohome system installed for around 4 or so months now but have only recently started paying attention to my boiler (due to other unrelated issues) therefore cannot be certain how it performed pre-Evohome running with a standard room stat and standard twist TRVs. I *think* your post has sem-reassured me (at least that makes three of us with similar behaviour: me, you and your neighbour!) though I can't help but thing this can hardly be efficient nor conducive to boiler life longevity?!

                          nb. you need to study the boiler firings and heat demand careful as there is also the separate 'feature' of the Evohome system sometimes only calling for heat for very short periods of time (1-3 minutes say) for the purposes of "topping up" a room to stop it dipping below a set point = the combination of this and our boilers seeming behaviour of heating up a circuit quickly then taking a break means the net result can often be numerous firings in close succession that are actually unrelated (as neither the boiler nor Evohome know what each other is thinking: the Evohome demands heat for x seconds without knowing whether the boiler is actually firing or taking a break, similarly the boiler doesn't know the Evohome is in say 30 seconds going to stop demanding heat so to hold out a little long). Throw the 2 minute pump-overrun into the mix and it can sure take a bit of thinking to know whether it's coming or going!

                          Comment

                          • SimonW500
                            Automated Home Jr Member
                            • Feb 2015
                            • 21

                            #43
                            Originally posted by jonstatt View Post
                            2) What is the frequency of updates from the temperature probe transmitter? They seem to be less frequent than 4 minutes. I have validated the signal strength is 5. Also, the updates to the gateway/app is VERY infrequent. Whereas if a radiator valve temperature updates on both controller and app within a couple of minutes, there is a massive lag for updates reaching the gateway/app for hot water. After having a shower, the controller read 54, whereas it took 15 minutes before the app showed this update!

                            3) In another thread I mentioned that nobody knows the duty cycles and minimum runtime the boiler is driven at in this mode as the options in the firmware disappear. I hope top brake will be able to find out (I know he is trying to get this information already, thanks ).
                            These two points are basically the reason I've just trawled through several hours worth of posts (learning lots of other interesting things on the way!)

                            WRT the HW I have also noted:

                            a) Where-as the rad temps report back to the controller every 4 minutes (assuming successful wireless comms etc) and within this boundary the controller is kept up-to-date, the HW temp seems to be updated less frequently on the controller (at a guess I'd say around every 8-12 minutes) and therefore shows more dramatic fluctuations
                            b) In terms of the iPhone App, while again the rad temps always match controller display (assuming a refresh is done.. either automatically polled or forcing a refresh by pulling down) - ie. I can hold the iPhone up next to the controller and the rad temps will read the same, the HW temp is usually out of sync (during temperature fluctuation) - ie. HW temp could have been 40C, has been heating for 20 minutes, controller displays 50C while iPhone App displays 42C - these figures remain out of sync for at least one 4 minute refresh cycle and play catch-up.
                            c) I suspect both these are more temperature display issues on both the controller and iPhone app, and that the controller is in fact working with the correct HW temperature in terms of knowing when it has suitably heated and therefore can cancel demand - I say this as on my install the HW rarely overshoots by more than a degree or two max, and in this instance I suspect is more to do with excess heat in my tiny airing cupboard! Following the example above I have seen instances whereby it's heating up to a setpoint of 60C, HW demand is cancelled with the controller still indicating 58 degrees and iPhone 50 degrees, then <10 minutes later the controller is updated to 60C and a little later the iPhone too (obviously the temperature is unlikely to be still rising significantly during this period as no heat is being called for).

                            I just put the above down to a bug or two - also noting the HW side seems to be controlled slightly differently to the rads (no optimal start etc which is a shame as I'd have thought this feature would be great for HW - you often know when you want your water to be hot for - the variable is what temperature it starts at depending on last use/heat) - IMO not exactly a showstopper as it seems to work regardless however it'd be nice if it were fixed.

                            Comment

                            • G4RHL
                              Automated Home Legend
                              • Jan 2015
                              • 1580

                              #44
                              A thought. My boiler is a 17 year old GlowWorm Ultimate. There is no temperature indicator on it and no way of knowing what the water temperature is set to. Just a knob to turn from off to maximum and no marks or indications in between. Should it be set to be maximum and left alone? There is no light to tell me when, if ever, it cuts out and the rare occasions it has ever done that are after power has been off and then restored. I then have to press the reset button and all is good again.

                              Comment

                              • jonstatt
                                Automated Home Guru
                                • Feb 2015
                                • 111

                                #45
                                Originally posted by G4RHL View Post
                                A thought. My boiler is a 17 year old GlowWorm Ultimate. There is no temperature indicator on it and no way of knowing what the water temperature is set to. Just a knob to turn from off to maximum and no marks or indications in between. Should it be set to be maximum and left alone? There is no light to tell me when, if ever, it cuts out and the rare occasions it has ever done that are after power has been off and then restored. I then have to press the reset button and all is good again.
                                On the Potterton Suprima the manual says the temperature range is from 50-82 degrees but there are no markings around the adjustment knob at all. I usually leave it in the mid-way setting (about 66 degrees), except in very cold winters where I up it to 2/3 of its range. I was told as a rule of thumb, a boiler should never be operated on its maximum temperature but 82 degrees sounds like a fairly normal boiler temperature to me.

                                Also my boiler is well known for short cycling due to problems with it's control boards. But I don't think that is what I am having as if the system is completely cold, the cycles are long and fine and the radiators get toasty like they are meant to. My short cycling only happens on a hot water only cycle once it has been heating for some time and I suspect this is due to a sizing issue with the hot water loop vs the boiler sizing, or an undersized differential in the thermostat. I am confident the flow rate is fine.

                                I did see the overheat stat operate twice in a strange circumstance where hot water was off, heating was off, but evo still throttled the heating relay for several minutes. In my boiler this results in a flashing red light but does not require a reset. It recovers by itself. Since I rebooted the EVOHOME controller by removing the batteries, it hasn't happened again since.

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