Evohome set to off but boiler fired up minutes later.

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  • robj20
    Automated Home Sr Member
    • Aug 2017
    • 76

    Evohome set to off but boiler fired up minutes later.

    Are there any reasons why after setting the heating to off the boiler minutes later would fire up? I don't just mean the pump overrun I mean flame on. The boiler showed heating on rather than the expected "Ready"
  • paulockenden
    Automated Home Legend
    • Apr 2015
    • 1719

    #2
    When you set the heating to off the low temp is passed to the HR92s (or whatever) sometime over the next five minutes. They then screw their valves down, then report back zero heat demand to the controller. Only when all zones are reporting zero will the controller tell the boiler relay to stop demanding heat.

    In other words, it can take a few minutes - even longer if a transmission gets lost.

    Comment

    • robj20
      Automated Home Sr Member
      • Aug 2017
      • 76

      #3
      Okay thanks only ideal were replacing a thermostor and with the heating turned it fired up a good few minutes later. I thought as much, sure I've had it before where I've set a new zone temp and that's took a while, not always instant.

      Comment

      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        #4
        If you're doing plumbing work on the heating system that requires the boiler and pump to definitely stay off I would not trust the Evohome system's built in Heating off or Away actions to do this.

        As explained there is a long sequence of events and wireless communication involved from you choosing the quick action until it is finally actioned, and it can in some circumstances not happen as expected, and at the very least will take a few minutes. If you're unlucky with the timing of the TPI cycle it may even appear to come back on after you have turned it "off", at least for a few minutes.

        Not to mention that someone could manually turn up an HR92 in any room while the system is being worked on and cause the boiler to be fired again even though the controller reports Off.

        Always isolate the mains supply to the boiler/pump/BDR91 etc before carrying out any electrical or plumbing work on the system. I'm surprised that your plumber did not do this. I have a fused switch beside my main BDR91 which cuts all the power to the whole heating system before the wiring centre, I use this before I do any plumbing work on the system to ensure the boiler and pump cannot start unexpectedly, and if I do any electrical work on it I also isolate it at the main consumer unit as well as at the fused switch for added safety.
        Last edited by DBMandrake; 11 December 2017, 10:07 PM.

        Comment

        • Dan_Robinson
          Automated Home Ninja
          • Jun 2012
          • 347

          #5
          Originally posted by DBMandrake View Post

          Always isolate the mains supply to the boiler/pump/BDR91 etc before carrying out any electrical or plumbing work on the system. I'm surprised that your plumber did not do this.
          Gotta love the irony of this advise given the fact that you DIY'ers are poking and prodding around in boilers that require certain checks when the covers are removed that you're not equipped to perform (Vaillant owners in particular ).
          Kind Regards - Dan Robinson (Jennings Heating Ltd)

          Comment

          • robj20
            Automated Home Sr Member
            • Aug 2017
            • 76

            #6
            Just to point out of was after the Thermistor was changed, which in my boiler only clips onto the pipe anyway.
            He was watching the flow and return temps then switched it off to see the pump overrun it then went off, but came back on which stumped him.

            Comment

            • DBMandrake
              Automated Home Legend
              • Sep 2014
              • 2361

              #7
              Originally posted by Dan_Robinson View Post
              Gotta love the irony of this advise given the fact that you DIY'ers are poking and prodding around in boilers that require certain checks when the covers are removed that you're not equipped to perform (Vaillant owners in particular ).
              How is it ironic ? I don't touch anything gas related on my boiler, that includes gas pipes/fittings, nor have I ever opened the seals on the fire box. What checks in particular are you referring to ? Since you don't even know what kind of boiler I have I suspect you're jumping to conclusions here...

              Comment

              • paulockenden
                Automated Home Legend
                • Apr 2015
                • 1719

                #8
                Originally posted by dan_robinson View Post
                gotta love the irony of this advise given the fact that you diy'ers are poking and prodding around in boilers that require certain checks when the covers are removed that you're not equipped to perform (vaillant owners in particular ).
                MRDA. ;-)

                p.
                Last edited by paulockenden; 12 December 2017, 01:08 AM.

                Comment

                • Dan_Robinson
                  Automated Home Ninja
                  • Jun 2012
                  • 347

                  #9
                  I suspect that arguing from a point of ignorance is a tad silly.

                  Just because YOU don't see what is needed does not mean it doesn't exist.

                  I know not, and care less what boiler you have DBM - I was replying, lightheartedly, to a general bit of advise about turning power off before working on a system (which is rubbish advise anyway as most checks on a modern boiler require live testing).
                  Kind Regards - Dan Robinson (Jennings Heating Ltd)

                  Comment

                  • DBMandrake
                    Automated Home Legend
                    • Sep 2014
                    • 2361

                    #10
                    Originally posted by Dan_Robinson View Post
                    I suspect that arguing from a point of ignorance is a tad silly.

                    Just because YOU don't see what is needed does not mean it doesn't exist.
                    Stooping to name calling and making claims of ignorance is not doing your argument any favour. It would behoove you not to make assumptions about what individual DIY'ers do or do not know about anything, and what they are capable of.
                    I know not, and care less what boiler you have DBM
                    Of course it matters. You're implying that "we" are routinely touching things that we shouldn't be, so I've asked you to provide a specific example of what your concerns are rather than a hand wavy "oh its too scary and dangerous, don't touch it, only us experts know what we're doing" assertions.

                    You're trying to imply even removing the covers on boilers needs gas safe training - nonsense. My boiler has a user removable cover (without screws) that exposes all the gubbins with exposed gas pipes, gas control unit, mains wiring, the whole lot all just sitting there in plain view - you have to take the front cover off and expose all this just to adjust the thermostat or light it!

                    I'm sure there are boiler designs where you can't get at some of the non gas stuff (plumbing, temperature sensors, PCB etc) without disturbing the gas pipes, gas control unit etc - in that case fair do's. But that is on a boiler by boiler basis, and depends on what exactly you're trying to get at in the unit.
                    - I was replying, lightheartedly, to a general bit of advise about turning power off before working on a system (which is rubbish advise anyway as most checks on a modern boiler require live testing).
                    So turning off the power before working on a system is bad advice ? Ok.... I'll file that piece of advice away in my waste paper bin...

                    I misread the original posters post - I thought they were breaking into the plumbing side of the system without ensuring the system was properly off - and as pointed out, Evohome has a much broader and greyer definition of "Off" than most standard control systems, so my advice was to make sure the system was really turned off at the mains before cracking open any plumbing, least the Evohome surprise you by turning the boiler back on and pumping water everywhere... I think this is a perfectly legitimate piece of advice when most people don't realise what "Off" really means on an Evohome.

                    And it should also be turned off before working on any of the electrical wiring, including changing a thermistor - anyone changing something like that without turning the power off isn't as qualified as they think they are.

                    Of course "checks" will require the power to be on again after the work is done. Duh.... so I'm not even sure why you mention that.

                    Carry on...
                    Last edited by DBMandrake; 12 December 2017, 02:05 PM.

                    Comment

                    • rcopus
                      Automated Home Jr Member
                      • Nov 2014
                      • 49

                      #11
                      Can’t you go back to DIYnot already?

                      The advise of isolating power to the boiler was fine. No need to get so offended and take the attitude everyone else is completely dumb just because you mess about with copper pipes and boilers for a living. Your jobs not at threat from the DIY’ers don’t worry!

                      Comment

                      • Dan_Robinson
                        Automated Home Ninja
                        • Jun 2012
                        • 347

                        #12
                        Originally posted by DBMandrake View Post
                        Stooping to name calling and making claims of ignorance is not doing your argument any favour. It would behoove you not to make assumptions about what individual DIY'ers do or do not know about anything, and what they are capable of.

                        Of course it matters. You're implying that "we" are routinely touching things that we shouldn't be, so I've asked you to provide a specific example of what your concerns are rather than a hand wavy "oh its too scary and dangerous, don't touch it, only us experts know what we're doing" assertions.

                        You're trying to imply even removing the covers on boilers needs gas safe training - nonsense. My boiler has a user removable cover (without screws) that exposes all the gubbins with exposed gas pipes, gas control unit, mains wiring, the whole lot all just sitting there in plain view - you have to take the front cover off and expose all this just to adjust the thermostat or light it!

                        I'm sure there are boiler designs where you can't get at some of the non gas stuff (plumbing, temperature sensors, PCB etc) without disturbing the gas pipes, gas control unit etc - in that case fair do's. But that is on a boiler by boiler basis, and depends on what exactly you're trying to get at in the unit.

                        So turning off the power before working on a system is bad advice ? Ok.... I'll file that piece of advice away in my waste paper bin...

                        I misread the original posters post - I thought they were breaking into the plumbing side of the system without ensuring the system was properly off - and as pointed out, Evohome has a much broader and greyer definition of "Off" than most standard control systems, so my advice was to make sure the system was really turned off at the mains before cracking open any plumbing, least the Evohome surprise you by turning the boiler back on and pumping water everywhere... I think this is a perfectly legitimate piece of advice when most people don't realise what "Off" really means on an Evohome.

                        And it should also be turned off before working on any of the electrical wiring, including changing a thermistor - anyone changing something like that without turning the power off isn't as qualified as they think they are.

                        Of course "checks" will require the power to be on again after the work is done. Duh.... so I'm not even sure why you mention that.

                        Carry on...

                        Not entirely sure where I was name calling?

                        But I suggest you read read my post carefully and comprehend.

                        Removing the outer cover on many boilers directly affects combustion. It also exposes components that can affect combustion if inadvertantly knocked.

                        The fire box (sic) doesn't need to be opened to affect the safe operation of a boiler.

                        My comment on my lack if interest in YOUR boiler is because I am speaking in the general, with Vaillant as an example.

                        But hey you crack on and over react.

                        But perhaps you can tell me how one measures ionisation on and isolated boiler?
                        Kind Regards - Dan Robinson (Jennings Heating Ltd)

                        Comment

                        • paulockenden
                          Automated Home Legend
                          • Apr 2015
                          • 1719

                          #13
                          Dan, your comments and advice here has been really great, but I’ve noticed a few of these “I’m a proper heating engineer and you're all just amateurs” posts (paraphrasing, of course). This isn’t the first thread where it's happened.

                          I hope you'll take this as friendly (and perhaps brutally honest) observation when I point out that it doesn’t really come across particularly well.

                          We all know you're a heating engineer - it says so at the bottom of each of your posts.

                          I hope you won’t take offence.

                          P.

                          Comment

                          • Dan_Robinson
                            Automated Home Ninja
                            • Jun 2012
                            • 347

                            #14
                            Originally posted by paulockenden View Post
                            Dan, your comments and advice here has been really great, but I’ve noticed a few of these “I’m a proper heating engineer and you're all just amateurs” posts (paraphrasing, of course). This isn’t the first thread where it's happened.

                            I hope you'll take this as friendly (and perhaps brutally honest) observation when I point out that it doesn’t really come across particularly well.

                            We all know you're a heating engineer - it says so at the bottom of each of your posts.

                            I hope you won’t take offence.

                            P.
                            I certainly don't hand offense. I'm merely pointing out that tinkering with electrics can have other effects. I'm not having a go at anyone, I'm hear to learn as well as give advice.

                            I'm sorry if the free advice I give based on nearly 20 years experience in the field results in answers people don't want to hear, but it is given from the standpoint of safety and having seen sme disastrous results of well meaning advice and/or work given by those who know less than they run.
                            Kind Regards - Dan Robinson (Jennings Heating Ltd)

                            Comment

                            • paulockenden
                              Automated Home Legend
                              • Apr 2015
                              • 1719

                              #15
                              Terms like "you DIYers" can come across as quite dismissive, when used in certain contexts.

                              The "free advice [you] give" is usually excellent - I don't think anyone is complaining about that. It's just those little digs that have started to appear recently that sometimes come across as... well... not what you'd expect in a friendly forum like this. That's all.

                              P.

                              p.s. I get told that sometimes my own posts come across a bit wrong too, so join the club!
                              Last edited by paulockenden; 13 December 2017, 10:42 AM.

                              Comment

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