Evohome new install

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  • jb80
    Automated Home Jr Member
    • Aug 2018
    • 11

    #16
    Originally posted by G4RHL View Post
    If I remember correctly for the hot water kit two methods can be used. The one I use which is the sensor strapped to the outside of the tank but an alternative is a sensor to go in the tank and am I right thinking that that goes in the top where you would put the immersion heater element?
    I have a similar situation with a Telford unvented cylinder. I am trying to work out where to install the Evohome insertion sensor probe. Should I replace the immersion heater element with the sensor?

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    • G4RHL
      Automated Home Legend
      • Jan 2015
      • 1580

      #17
      Originally posted by jb80 View Post
      I have a similar situation with a Telford unvented cylinder. I am trying to work out where to install the Evohome insertion sensor probe. Should I replace the immersion heater element with the sensor?
      If you do you will have no emergency backup to heat the tank. I am sure someone here has done this. I just used the external sensor which was fine. No issues.

      Comment

      • snake007uk
        Automated Home Lurker
        • Jul 2019
        • 9

        #18
        Originally posted by G4RHL View Post
        If you do you will have no emergency backup to heat the tank. I am sure someone here has done this. I just used the external sensor which was fine. No issues.
        I know its been a while, but I thought i'd reply to the post.

        So in my case, the engineer cut a small hole in the outer insulation of the tank and put the sensor inside. This was then cover up. Its been working fine ever since (been three years now).

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        • jb80
          Automated Home Jr Member
          • Aug 2018
          • 11

          #19
          Originally posted by jb80 View Post
          I have a similar situation with a Telford unvented cylinder. I am trying to work out where to install the Evohome insertion sensor probe. Should I replace the immersion heater element with the sensor?
          Thank you for your help, though since I have an unvented cylinder I need to insert the probe into the cylinder. I actually worked out the solution which wasn't too difficult. I removed the existing Telford Aquastat thermostat and fed the Evohome sensor probe through the Aquastat using the existing holes. Therefore the Telford Aquastat remains as the high temperature safety cut-out and the Evohome sensor is used for normal control.

          Photos attached of the final solution. I hope someone finds it useful

          20220714_205323.jpg

          20220714_205338.jpg

          Comment

          • Backofthenet
            Automated Home Jr Member
            • Nov 2021
            • 14

            #20
            Hi - I realise this is an old post but wonder if JB80 is still reading - I noticed for your DHW you simply fitted the HW sensor through a hole in your current sensor set up.

            Can you elaborate on your set up please i.e. the CS92A and hoe the BDR91 is used for the HW (is it attached to an existing backplate you have?) I have a virtual identical set up as you and am looking to fit the Evohome HW kit as you have
            Last edited by Backofthenet; 22 December 2022, 06:47 PM.

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            • jb80
              Automated Home Jr Member
              • Aug 2018
              • 11

              #21
              I temporarily removed the existing Telford Aquastat cylinder thermostat (ALTTGSTAT), removed the cover and then fed the Honeywell insertion sensor (F50079510-001) through the hole of the Telford stat. Reassembled and then fed both temperature probes back into the cylinder pocket. Honeywell insertion sensor is wired to the Evohome hotwater wireless sensor. By doing so, it maintains the thermal cut-out with separate temperature feedback to Evohome for control.

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              • Backofthenet
                Automated Home Jr Member
                • Nov 2021
                • 14

                #22
                Thanks for the quick reply - quite ingenius and i understand that bit.

                It's what happens after - I think you have wired the sensor probe to a CS92A thermostat?

                Is that CS92A then bound to a BDR91? Its more the bit about how the thermostat links to the evohome controller so the controller can control your hot water.

                I have the evohome controller bound to a BDR91 - the BDR91 is linked to my backplate for CH control so I am looking to extend the evohome controller to control my DHW. My DHW is still controlled via a honeywell ST9400C two channel programmer for DHW

                apologies if I sound a bit dumb
                Last edited by Backofthenet; 23 December 2022, 03:56 PM.

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                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  #23
                  Temp probe to CS92A. Then use Evohome to enable HW. The sensor is the CS92A and the actuator is a BDR91 that operates your HW zone valve.

                  Comment

                  • Backofthenet
                    Automated Home Jr Member
                    • Nov 2021
                    • 14

                    #24
                    Brilliant - so I already have a BDR91 which fits to the Y Plan backplate to control the Central Heating via Evohome controller - can I wire the same BDR91 to the Y Plan backplate for DHW connections or do I need to use a separate BDR91?

                    Comment

                    • bruce_miranda
                      Automated Home Legend
                      • Jul 2014
                      • 2307

                      #25
                      You will need a separate BDR91. It will be included in the HW kit.

                      Comment

                      • Backofthenet
                        Automated Home Jr Member
                        • Nov 2021
                        • 14

                        #26
                        Thanks

                        a small project for after Christmas

                        If I post pictures and explanation of my current set-up after the Christmas break would appreciate some input on what wires go where for the DHW BDR91.
                        Last edited by Backofthenet; 24 December 2022, 08:23 PM.

                        Comment

                        • Backofthenet
                          Automated Home Jr Member
                          • Nov 2021
                          • 14

                          #27
                          Hi Bruce_Miranda

                          So my current set up is as follows which I believe is Y Plan configuration

                          I have an ST9400C 2 channel Programmer wired to an industry standard back plate which still controls HW. Please see Pic of backplate
                          I also have a BDR91 wired into the same backplate for controlling the CH and the ST9400C is effectively set to off for the CH channel such that all Rad's are controlled via Evohome controller bound to the BDR91.

                          The BDR91 is wired into N, L and Position 4 ( CH ON) on the backplate

                          So for the second BDR91 will it be a case of wiring into N, L and Position 3 (HW ON) then Binding the second BDR91 to Evohome controller and setting up HW control via Evohome controller / setting HW channel to off on ST9400C?

                          PS - Understand I have to also fit the temp probe and CS92A to HW Cylinder and then bind CS92A to evohome controller for temp monitoring.

                          IMG_6007.jpg

                          Comment

                          • bruce_miranda
                            Automated Home Legend
                            • Jul 2014
                            • 2307

                            #28
                            Yup all correct. And doing it this way ensures that any protection stats for the HW cylinder are wired in series to the BDR91, which is required by the regs.

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                            • MadeTomatoHue
                              Automated Home Jr Member
                              • Nov 2022
                              • 47

                              #29
                              Originally posted by Backofthenet View Post
                              So for the second BDR91 will it be a case of wiring into N, L and Position 3 (HW ON) then Binding the second BDR91 to Evohome controller and setting up HW control via Evohome controller / setting HW channel to off on ST9400C?
                              I think the main thing to be aware / cautious of is to only place the BRD across the live feed to the original controller backplate and its HW output. That ensures any additional over temperature safety control on the HW cylinder remains in place. "Borrowing" a different live or taking the BRD back to the wiring centre in a different way might bypass it.

                              If you don't remove the original adjustable cylinder stat you may want to adjust it upwards to ensure the new insertion sensor can reliably reach target temperature. If it cuts off HW heating at ~57C while Evohome is waiting to reach 60C then (with DHW priority) you may be without CH for a while. That's probably a "safer" option that trying to remove it from the wiring while leaving the fixed safety stat in place - which is typically in series with the adjustable one.

                              Comment

                              • mtmcgavock
                                Automated Home Legend
                                • Mar 2017
                                • 507

                                #30
                                For a Unvented Cylinder the High Limit stat MUST be wired in series with the BDR91, and the Cylinder must have it's own 2 Port valve (Not allowed a 3 port).

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