Evohome Self Install

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  • crh
    Automated Home Jr Member
    • Oct 2014
    • 16

    Evohome Self Install

    Hello Everyone,

    Previously had evohome in our old house which we loved and we have now moved to a new house. I'm having real difficult getting hold of a installer in south wales. Most of the recommended installers on the honeywell list for our area won't return our calls or haven't installed evohome in a long time and don't really want to do it

    We have a five bed house that has x2 thermostats, Combi boiler and kingspan range tribune xe

    Question being with this setup is this something i can self install or would we need a plumber
    Last edited by crh; 9 July 2018, 10:19 AM.
  • G4RHL
    Automated Home Legend
    • Jan 2015
    • 1580

    #2
    You don’t need a plumber but you might want an electrician if you are not confident doing the wiring. The “plumbing” bit is no more than taking off the old TRVs and putting on the Evohome ones. No draining down. Its a 60 second job. The wiring is little more complex but not overly so. In effect the relay or relays will be the switches for the boiler as opposed to the original thermostat doing it. Two thermostats sounds like you may have 2 zones already and whether professional help is needed depends on your intention and whether the existing zones are controlled by a bypass valve. I would be inclined to start by ensuring the house is one zone and then having done that add the Evohome TRVs creating new zones - each room etc. I am sure there is somebody in this forum who can better explain what needs to be done than I can!

    Comment

    • ojock
      Automated Home Jr Member
      • Jul 2018
      • 10

      #3
      It's not necessary a plumber, but perhaps an electrician with heating experience.

      I've just had a new Evohome install done. The electrician i used had never installed an Evohome before.

      I have a Worcester system boiler and Worcester unvented cylinder, I bought a Evohome connected pack, hr92 trvs and the HW kit.

      I have 3 motorised valves, one for HW, one for central heating and one for ufh. I simply gave 3 bdr91 relays to the electrician + a Honeywell junction box, just told him to wire it up. No drama, think this is bread and butter stuff. After all, it is just a switch which opens the valve, the boiler then fires up and the pump starts.

      As my install was in unheated garage, I also got him to fit a honeywell frost protection kit.

      The only tricky bit he hasn't done properly is the HW kit, he fitted the cs92 sensor but not the high limiter, so I'm having that retrospectively fitted.

      You might need some Honeywell Valencia valve bodies as I understand not all of them fit hr92s (even though the hr92s do come with adapters), for that I did get a plumber to swap the valve bodies out.

      All the binding,config i did myself. That was the hardest part for me - getting the config right to work with my HW kit and ufh.

      Saying all that, I know nothing about combi boilers and your kingspan, so worth doing a bit more research

      Comment

      • gordonb3
        Automated Home Ninja
        • Dec 2016
        • 273

        #4
        Can't really answer this with the supplied information.

        You should start with verifying that the HR92s can be fitted to your valve bodies. Are they even pin-operated? I know there are adapter rings for specific other brands like Danfoss, but personally I think you should stay away from those and stick to the screw on versions. Yet again there are two versions here: 30mm and 28mm. The 30mm are a direct fit to the HR92s. If you have 28mm bodies you can get an alternative base plate for the HR92 (part number ACH-28).

        If you got one right hand and one left hand then replacing valve bodies shouldn't be much of an issue as this is all compression fitting and screw on (be sure to use plumbers hemp here - not the white tape). Electrics is also no big magic when you are replacing a standard two wire thermostat - just attach the BDR-91 outputs to the two wires to which the original thermostat is connected. If you are using the wall mount for the Evohome controller then do note that the tiny wires running to the thermostat are not suited to carry 230V. You have two options here: either run new wires or detach the transformer from the wall mount and mount it somewhere near the boiler to use the original wiring.

        Comment

        • crh
          Automated Home Jr Member
          • Oct 2014
          • 16

          #5
          Thanks for the replies, HR92's kit the current rads so that isn't a problem

          looking at the hot water kit at the moment which has the strap on sensor or the insertion sensor. anyone with experience of this for a kingspan range tribune?

          Comment

          • paulockenden
            Automated Home Legend
            • Apr 2015
            • 1719

            #6
            Originally posted by ojock View Post
            The only tricky bit he hasn't done properly is the HW kit, he fitted the cs92 sensor but not the high limiter, so I'm having that retrospectively fitted.
            Sidetracking slightly, but is that REALLY needed? I can see the need with an immersion, but when the heat source is a loop off the boiler so it never really going to be higher than, say, 90 degrees, is there really a chance of an unvented tank becoming a bomb? (and besides, there should be a pressure and temp relief valve fitted anyway).

            I know people say that you MUST use a high temp cutout, but to me it just seems like one of those things that people say and everyone else repeats!

            Am I wrong?

            P.

            Comment

            • ojock
              Automated Home Jr Member
              • Jul 2018
              • 10

              #7
              Thanks Paul. I don't know if it's really needed, from what I've read, it's just another safety feature?

              It does make me wonder the way you've explained it.

              Saying that, it'll cost me less than £90 to put one in, I'm not sure for that amount I'm too concerned it's just more of a comfort blanket than something that is critical.

              Comment

              • paulockenden
                Automated Home Legend
                • Apr 2015
                • 1719

                #8
                I'm certainly not advocating the people shouldn't do it. Simply questioning the received wisdom in this area!

                Comment

                • DBMandrake
                  Automated Home Legend
                  • Sep 2014
                  • 2361

                  #9
                  Originally posted by paulockenden View Post
                  Sidetracking slightly, but is that REALLY needed? I can see the need with an immersion, but when the heat source is a loop off the boiler so it never really going to be higher than, say, 90 degrees, is there really a chance of an unvented tank becoming a bomb? (and besides, there should be a pressure and temp relief valve fitted anyway).

                  I know people say that you MUST use a high temp cutout, but to me it just seems like one of those things that people say and everyone else repeats!

                  Am I wrong?
                  Risk of scalding ?

                  Comment

                  • Edinburgh2000
                    Automated Home Guru
                    • Dec 2016
                    • 134

                    #10
                    Originally posted by paulockenden View Post
                    Sidetracking slightly, but is that REALLY needed? ...... is there really a chance of an unvented tank becoming a bomb?
                    I don't see the secondary cut-out as a safety feature, more a backup as the CS92 is very unreliable. I regularly get overshoots from the CS92, which can take up to 30 minutes to catch up with the real measured temperature. In the meantime, my mechanical thermostat initiates closure of the valve to stop any overheating. I would not want to rely on the CS92 alone as I would get very variable hot water temperatures.

                    Comment

                    • paulockenden
                      Automated Home Legend
                      • Apr 2015
                      • 1719

                      #11
                      Originally posted by DBMandrake View Post
                      Risk of scalding ?
                      Yes, you're probably right. Unless there's a blend valve on the tank output.

                      Comment

                      • mtmcgavock
                        Automated Home Legend
                        • Mar 2017
                        • 507

                        #12
                        There's a number of reasons, although it's part of the Unvented regulations that all heat sources have a cut out device in addition to the standard temperature control. And yes I have seen them cut out on with a boiler when something somewhere has failed, usually when someone else has fitted something incorrectly! But you are quite correct, it does take a number of devices to fail before it should ever really come into action, however there's no harm in having it there.

                        It's also prevents it overheating if the CS92 fails, which they can be a bit problematic from time to time, although touch wood mine has been OK for a while.

                        Comment

                        • DBMandrake
                          Automated Home Legend
                          • Sep 2014
                          • 2361

                          #13
                          Originally posted by paulockenden View Post
                          Yes, you're probably right. Unless there's a blend valve on the tank output.
                          For what it's worth I have a vented cylinder (which was originally just gravity circulation before I converted it to S-Plan) and I don't have an additional cutout, (technically it isn't required to have one) however I tend to have the flow temperature set to 65 in summer and 70 in winter, and never any higher than 75. When hot water heating is occurring it's not boosting the flow to 90 like many modern boilers do, it just stays at what it's set to for heating.

                          I have an external digital flow thermostat I added connected in series with the original mechanical flow stat in the boiler, with the digital stat controlling the temperature and the mechanical stat turned up right up to 82 as a safety cutoff for the boiler in the event of the external stat failing. For a while I had the switch in the hot water zone valve configured to bypass the external stat thus boost the flow temperature to 82 during hot water heating, however I found it wasn't really necessary, and put a lot of unnecessary stress on the boiler which has a tendency to kettle going that high.

                          So I ripped that boost wiring out and also set a high limit on my digital stat to stop anyone setting it higher than 75.

                          So I do rely on the flow temperature limit preventing hot water getting dangerously hot - typically it can't get more than about 5C below the peak flow temperature so 65C when flow is set to 70C, and it does take it a long time to get those last few degrees.

                          The problem with adding an additional safety stat in my circumstances is that they typically have an 8C hysteresis. So in order for it not to interfere with my normal 54C hot water set point I'd have to set it to at least 62C, or in practice say 65C - by which time its not really giving me any additional protection over relying on the flow temperature limit. On the other hand if my boiler was boosting to 80/90C for hot water heating as many do I would definitely fit an additional stat for the times when the CS92 malfunctions.

                          I really wish Honeywell had not designed a hot water control system that relies on a wireless communication loop from a battery powered device (CS92) to a sometimes battery powered device (controller) back to the relay. Such as design is just never going to be 100% reliable.

                          Instead of a CS92 and BDR91 there should have been a single hot water control relay box that had both the relay and temperature sensor input in the same box, mains powered and hardwired. The controller then just tells the box what the hot water temperature and differential should be, then the box can sense the temperature and control the relay directly without any intervention from the controller, just providing notification back to the controller so the controller is informed of what's going on. (And can control the boiler control relay if one is fitted)

                          It's something Honeywell could theoretically do with a firmware update in the controller to support a new combined hot water control device, but I'm not holding my breath!
                          Last edited by DBMandrake; 14 July 2018, 08:09 AM.

                          Comment

                          • paulockenden
                            Automated Home Legend
                            • Apr 2015
                            • 1719

                            #14
                            I agree that the CS92 is quite a weak point in the Evohome system.

                            Trouble with combining the sensor and relay in one box is that they might need to be in different places.

                            Comment

                            • DBMandrake
                              Automated Home Legend
                              • Sep 2014
                              • 2361

                              #15
                              Realistically how far apart would they need to be ? In my case they are in the same boiler closet. Even if it was a cylinder in a loft space with a boiler on the ground floor you might need say 4 metres of figure 8 flex to extend the sensor.

                              The relatively high resistance of the sensor used means that a few ohms of cable resistance would have negligible effect on the temperature reading, so I don't see it as a major issue in most installations, given the increased reliability and robustness it would offer.

                              Comment

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