UFH - EvoHome and reluctant plumber

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  • kevinsmart
    Automated Home Ninja
    • Sep 2018
    • 257

    #16
    The HM80 is a fuzzy logic controller, so I am hoping it will offer better temperature control for a single zone UFH, than BDR91 TPI, just like you see with the HCC80.



    It will be a while before I know though, as it is on back order with Honeywell via the Evohomeshop.

    Comment

    • mtmcgavock
      Automated Home Legend
      • Mar 2017
      • 507

      #17
      Run 3 UFH separate zones off BDR91s and have no issues with them, temperature control is just fine. IMO the HCC80 is a waste unless you have 5+ zones.

      Comment

      • kevinsmart
        Automated Home Ninja
        • Sep 2018
        • 257

        #18
        What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?

        Comment

        • rvb99
          Automated Home Sr Member
          • Oct 2017
          • 74

          #19
          Originally posted by kevinsmart View Post
          What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?
          Fot us we only have a day and night setting for the ufh zones. We have 14 radiators in the system controllered by HR92s ( some in groups using Y87RF
          sensors ) . No open therm. Input temp to ufh mixing sysyem 65-70 deg Manifold output temp approx 45deg. Manifold return temp approx 38deg. HCC80 ufh controller , operating 2 zones with 7 pipe runs of 80 Metres. However each set up is goîng to vary quite a bit. If pipe length are similar it makes settîng up of the flow rates easier to get to the in/out temp differentials. We also have a separate safety thermostat attached to the manifold output set to shut down the whole ufh system if it gets to 50deg. This is to protect the floor but also for health issues. Too high ufh temp can be bad for some people’s circulation.
          Last edited by rvb99; 26 February 2019, 09:58 PM.

          Comment

          • mtmcgavock
            Automated Home Legend
            • Mar 2017
            • 507

            #20
            Originally posted by kevinsmart View Post
            What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?
            Runs 24/7 during the winter at 21oc, Spring/Autumn it drops down a couple of degrees at night to 19oc. Mixture of UFH and rads. Manifold with mixing valve set to around 60oc. We have had it lower before but prefer a warmer floor so run it higher. Not on opentherm, boiler flow at 70oc.

            Comment

            • kevinsmart
              Automated Home Ninja
              • Sep 2018
              • 257

              #21
              I think the key difference is that I am only heating our UFH zone in the evening. In an experiment, running 24/7, Evohome could maintain a stable temperature when the set point was set to the current temperature.

              It doesn’t matter if the temperature differential is 3 degrees or only 0.5 degrees when heating starts, by 9pm when optimum stop kicks in the zone is 1 degree above the set point.

              Comment

              • mtmcgavock
                Automated Home Legend
                • Mar 2017
                • 507

                #22
                Originally posted by kevinsmart View Post
                I think the key difference is that I am only heating our UFH zone in the evening. In an experiment, running 24/7, Evohome could maintain a stable temperature when the set point was set to the current temperature.

                It doesn’t matter if the temperature differential is 3 degrees or only 0.5 degrees when heating starts, by 9pm when optimum stop kicks in the zone is 1 degree above the set point.
                Why are you only running it in the evening? You aren't meant to run UFH for short periods otherwise you won't get the correct heat out of it. In effect you are heating a big surface area that holds it's heat. Heating it for short periods you are never going to get the correct temperatures. You can't operate it like radiators.

                Comment

                • kevinsmart
                  Automated Home Ninja
                  • Sep 2018
                  • 257

                  #23
                  Originally posted by mtmcgavock View Post
                  Why are you only running it in the evening? You aren't meant to run UFH for short periods otherwise you won't get the correct heat out of it. In effect you are heating a big surface area that holds it's heat. Heating it for short periods you are never going to get the correct temperatures. You can't operate it like radiators.
                  I don’t see that as the issue. Evohome should be able to balance any heat loss for any zone when the set point is reached. As it stands, at set point, the zone still has a 50% heating demand leading to the overshoot. At 1 degree over there is still a 20% demand, which doesn’t make sense considering the heat retention. It should learn that much less energy is needed when the room is up to temperature, but it isn’t doing a good job and is wasting energy.

                  I expected much better temperature control from Evohome. It copes well with HR92 zones, but is unable to adapt to my UFH zone. I could program a Raspberry Pi to do a better job. 😀

                  Comment

                  • Neamac
                    Automated Home Lurker
                    • Mar 2018
                    • 2

                    #24
                    Hope you don't mind me carrying on with the BDR91 vs HCC80 theme. I am about to add UFH to my existing Evohome system that has 11 Rads with HR92s fitted and it works well. I have a 4 port manifold for UFH for a kitchen and utility room, 3 pipe runs for kitchen (72m, 80m, 81m) & Utility 67m. I was thinking about using 1 BDR91 running the 4 ports as 1 zone with a UFH pump and a mixer valve. There is no motorized zone valve or actuators other than manual adjuster on the manifold.
                    If I wired the BDR to switch on the UFH pump for all the ports on the manifold and control the temperature with a Y87RF thermostat would this work ok? Thanks in advance - I hope I haven't hijacked the thread!

                    Comment

                    • kevinsmart
                      Automated Home Ninja
                      • Sep 2018
                      • 257

                      #25
                      Originally posted by kevinsmart View Post
                      I have a single zone twin loop UFH setup controlled via Y87RF and BDR91 in my new well insulated extension. BDR91 activates the pump and manifold valves are left open.

                      As it’s in combination with 26 rads, there is a thermostatic mixing valve to reduce the flow temperature. Boiler is Intergas HRE40 SB with OpenTherm module, and an outdoor sensor (unfortunately weather compensation doesn’t work with Evohome OpenTherm support though).

                      I’m not happy with the UFH setup for a few reasons:

                      1. The mixing valve intermittently emits a high pitched whine, appears to be when the flow temperature matches its set point.
                      2. Wife complains about 1!
                      3. Poor temperature control. Evohome indicates a 40-60% demand for the zone even when the set point is reached, as a result there is an overshoot. Optimum start typically pre-heats for 1.5 hours, temperature increases to more than 1 degree above the set point after a few more hours, still with <20% demand, then optimum stop kicks in 1 hour before set back. I’ve tried reducing the mixing valve set point temperature but Evohome seems unable to adapt.

                      Primarily because of 2, I’m going to replace with an HM80 controlled rotary actuator and flow temperature sensor. I hope this will work better with OpenTherm and provide more accurate temperature control.
                      It took a while (largely due to lack of support for this in the UK) but I now have the HM80 controlled solution for my single-zone UFH in place. And it works great, I no longer see the 1 degree overshoot, the set temperature is reached and maintained within around 0.1 degrees over several hours.

                      It's entertaining watching the controller make quiet regular small adjustments to the rotary valve to maintain temperature.

                      One interesting observation was this freezing morning with a 15C setback temperature and 15.5C measured temperature, the controller decided to run the pump, with Evohome indicating a 0% heating demand (but other zones heating). This appeared to stop further heat loss in the zone.

                      Comment

                      • kimber.kimber
                        Automated Home Sr Member
                        • Jan 2017
                        • 89

                        #26
                        Hope you don’t mind me piggy backing on this, but I have wet UFH as a single zone, two loops controlled using a zone valve set up. It’s in conjunction with the rest of the house on radiators. The system runs on optimum start.

                        My question is about scheduling. With the temp drop over the last few days, it’s taken a while on warm up. Normal temp is 20degs, with a setback to 17degs when we’re not using the room. Last night it didn’t hit its set temp, only getting to 19degs.

                        Is it best to have the schedule adjusted to get this the sole priority when warming up? My feeling is that it shouldn’t matter as the water temps are significantly lower than to the rest of the system. Or do you think it’s the optimum start that’s causing the issue, because of the large lag with the heat cycle?

                        Cheers,

                        Ian

                        Comment

                        • kevinsmart
                          Automated Home Ninja
                          • Sep 2018
                          • 257

                          #27
                          Originally posted by kimber.kimber View Post
                          Hope you don’t mind me piggy backing on this, but I have wet UFH as a single zone, two loops controlled using a zone valve set up. It’s in conjunction with the rest of the house on radiators. The system runs on optimum start.

                          My question is about scheduling. With the temp drop over the last few days, it’s taken a while on warm up. Normal temp is 20degs, with a setback to 17degs when we’re not using the room. Last night it didn’t hit its set temp, only getting to 19degs.

                          Is it best to have the schedule adjusted to get this the sole priority when warming up? My feeling is that it shouldn’t matter as the water temps are significantly lower than to the rest of the system. Or do you think it’s the optimum start that’s causing the issue, because of the large lag with the heat cycle?

                          Cheers,

                          Ian
                          Ian, you can configure how many hours optimum start will pre-heat, maybe you need to increase that parameter.

                          Comment

                          • kimber.kimber
                            Automated Home Sr Member
                            • Jan 2017
                            • 89

                            #28
                            Originally posted by kevinsmart View Post
                            Ian, you can configure how many hours optimum start will pre-heat, maybe you need to increase that parameter.
                            Thanks Kevin, I had forgotten about that. I'll see how it goes over the next couple of days and adjust that if required.

                            I'm assuming even when you add a new zone, the learning still takes place, and it is continually learning, taking into account the conditions?

                            Comment

                            • kevinsmart
                              Automated Home Ninja
                              • Sep 2018
                              • 257

                              #29
                              Originally posted by kimber.kimber View Post
                              I'm assuming even when you add a new zone, the learning still takes place, and it is continually learning, taking into account the conditions?
                              Yes, that should be the case.

                              Comment

                              • BuxtonJim
                                Automated Home Jr Member
                                • Aug 2018
                                • 45

                                #30
                                I started out with my wet UFH plumbed into a radiator circuit but was never completely happy with its controllability. I know in theory that it should be independent and fine if all rads have HR92s fitted, it seems to behave perfectly now it's plumbed back directly to the boiler. Temperatures are maintained to +/- 0.5 and optimum start and stop set to 1hr work really well. The ufh zone is flagged so there's real opportunity for overshoot but the optimised stop seems to handle this.

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