EvoHome Advice

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  • yngndrw
    Automated Home Jr Member
    • Mar 2018
    • 12

    #16
    Sorry yes I meant a BDR91, I copied the wrong code - I should probably stick to the names rather than the codes! My proposal was just to replace the timer with the BDR91 relay and use the existing thermostat.

    The high limit thermostat is built into the user-adjustable thermostat that I have, so I'd either have to use both together or find another limit thermostat if I were to use the EvoHome HW kit to control the temperature. I think it's easier just to leave it in circuit if I decide to go with the EcoHome controlling the HW temperature as well as the time.

    Comment

    • HenGus
      Automated Home Legend
      • May 2014
      • 1001

      #17
      Taking it out will probably invalidate your unvented cylinder warranty. It is also there if Evohome fails and you want to use the electric immersion heater.

      Comment

      • yngndrw
        Automated Home Jr Member
        • Mar 2018
        • 12

        #18
        Good point, I think they do sell them as a partially-made kit so it was likely fitted from the factory so it likely would affect the warranty - A little annoying as that's the only thermostat port on the cylinder but I probably don't need the EvoHome to control the water temperature, just the time for hot water.

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #19
          Originally posted by yngndrw View Post
          Good point, I think they do sell them as a partially-made kit so it was likely fitted from the factory so it likely would affect the warranty - A little annoying as that's the only thermostat port on the cylinder but I probably don't need the EvoHome to control the water temperature, just the time for hot water.
          If you go that route you still need the temperature sensor otherwise it won't operate the hot water relay, so you'd need to leave it connected but lying loose somewhere. And the Evohome would always report the wrong temperature and always (when scheduled on) call for heat to heat up the cylinder.

          The only thing that would prevent the boiler from firing is if the boiler was fired through the orange wire for the hot water zone valve, because the cylinder thermostat would prevent the zone valve from opening. Not an ideal solution really.

          Comment

          • yngndrw
            Automated Home Jr Member
            • Mar 2018
            • 12

            #20
            Thanks that's good to know, I thought the EvoHome could just use the relay without knowing the temperature so that's a shame. I guess I could strap the sensor to the hot water outlet of the cylinder so it's at least a ballpark figure, but still just use it for scheduling. Not ideal as you say, but it will let me try the system and I can then get someone in to fit the sensor properly and switch to a more suitable limit thermostat if needed.

            Comment

            • HenGus
              Automated Home Legend
              • May 2014
              • 1001

              #21
              This is a pretty daft discussion as for 99% of the time the HW kit works very well. Having a temperature differential range also reduces energy use. I have set my differential at 5C as 55C is the minimum flow temperature for my shower. Occasionally, I get a temperature overshoot of 1C. Comms faults are rare and normal service is usually restored within the hour.

              Comment

              • yngndrw
                Automated Home Jr Member
                • Mar 2018
                • 12

                #22
                The only problem that I have with the HW kit is the installation, I don't have a second thermostat pocket for the HW kit and the existing thermostat includes the limit stat so I'd have to have that replaced with something that allows the HW kit's sensor as well. I'll have to have a look and see what's available.

                Comment

                • HenGus
                  Automated Home Legend
                  • May 2014
                  • 1001

                  #23
                  My OSO cylinder doesn’t have any ports. The sensor has just been pushed up (at an angle) underneath the installation foam with access via the electrical panel. It needs to be pushed up to the correct height as per the user guide.

                  Comment

                  • yngndrw
                    Automated Home Jr Member
                    • Mar 2018
                    • 12

                    #24
                    Taking a closer look at my cylinder, I don't have an electrical panel which breaches the insulation, except for the immersion heater.

                    I have however noticed that the ESi thermostat that I have has enough space inside to put the additional sensor into the thermostat pocket, so I should be fine after all:

                    Comment

                    • HenGus
                      Automated Home Legend
                      • May 2014
                      • 1001

                      #25
                      Good new. Whatever you decide, make sure that the CS92 etc are separated from each other and other bits of metal etc (if possible) by at least 300mm. If you decide to go for an OT Bridge, my installer's advice was to place it well away from everything else. My Bridge is located in the corner of the integral garage where the boiler is located with about 15 foot separation.

                      Comment

                      • yngndrw
                        Automated Home Jr Member
                        • Mar 2018
                        • 12

                        #26
                        Thanks, I'll be sure to do that. Fortunately I have lots of space in the cupboard by the cylinder, but I might need to have a think about where the OT bridge could go that's not next to the boiler.

                        Comment

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