Pump overrun

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • Norfolkboy
    Automated Home Jr Member
    • Nov 2016
    • 43

    Pump overrun

    I’m not sure if i have lost my pump overrun feature, i had the hot water on today and boiler was running at 78C, Evo HWstat reached temp and boiler cut off, and then the pump switched off about 10 seconds later. I would have thought at such a high temp i would have seen it stay on much longer like it did pre evo.

    I had pump overrun switched on at the evo controller for 2 minutes, and the BDR did stay on with the valve open, but the pump being powered by the boiler was off, so pointless.

    Just thinking as i have disconnected the orange and grey cables from the valves in the junction box, have i now stopped the overrun? Looking at Honeywells pump overrun wiring the Orange cables are connected to the switched live on the boiler. but Fig 9 in the evo book says "if a wireless boiler relay is used the Grey/Orange cables are not required"

    S Plan design, with Opentherm controlling the boiler and BDR runnin ghot water valve.

    Many thanks
  • DBMandrake
    Automated Home Legend
    • Sep 2014
    • 2361

    #2
    There's no "pump overrun" setting in Evohome, you might be thinking of hot water overrun - what that does is when the hot water temperature is reached it will turn off the boiler demand immediately but leave the hot water zone valve open for the additional time that you specify. It will not have anything to do with pump overrun, and it requires that your system already has some pump overrun to be effective.

    Evohome doesn't control pump overrun - that's entirely up to your existing boiler and possibly wiring centre if you have an external pump. So we'd need to know how your pump is powered, whether it's built into the boiler or external, whether there is any external timer involved etc.

    On many boilers the pump is controlled by the boiler and the overrun is not a timer but is based on the measured flow temperature where the pump runs on until the flow temperature is below a certain temperature.

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2307

      #3
      Boiler Make and Model?

      Comment

      • Norfolkboy
        Automated Home Jr Member
        • Nov 2016
        • 43

        #4
        Viessman 100w system boiler. the External Pump overrun worked fine before Evo was fitted, but has i have removed the orange cables coming from the valves as per the instructions, and looking at wiring diagrams these would go to the switched live of the boiler. Does that make sense?
        Last edited by Norfolkboy; 25 November 2016, 09:37 PM.

        Comment

        • Little Tinker
          Automated Home Jr Member
          • Nov 2016
          • 38

          #5
          When you removed the grey and orange wires on the junction box did you wire the relay in at the same points? If so then whatever was driving the pump over run ought to still be getting the signals it used to get.

          If you wired the relay in somewhere else then maybe something lost the signal it previously got.

          Did the orange wires perhaps used to signal the overrun controller to fire boiler and pump, and turn boiler off before pump? But new wiring from relay is going direct to boiler and pump?

          Comment

          • bruce_miranda
            Automated Home Legend
            • Jul 2014
            • 2307

            #6
            Pump overrun on a system boiler should be controlled directly by the boiler either on time or temperature. So some else has been disconnected that shouldn't have been.

            Comment

            • Norfolkboy
              Automated Home Jr Member
              • Nov 2016
              • 43

              #7
              think i may have solved the issues, looking at techincal manual fo rmy boiler it says:


              OpenTherm signal -Pump off delay - 20 seconds

              If its running on the standard room thermostat (like it used to) then the pump off delay is 4 minutes.
              I dont undertand why Opentherm control would be so short, in practise it can fire the boiler to hotter than it use to go with DHW demand (78c) and then switch off
              Last edited by Norfolkboy; 29 November 2016, 01:53 PM.

              Comment

              • bruce_miranda
                Automated Home Legend
                • Jul 2014
                • 2307

                #8
                That's got to be a configurable parameter.

                Comment

                • Norfolkboy
                  Automated Home Jr Member
                  • Nov 2016
                  • 43

                  #9
                  Originally posted by bruce_miranda View Post
                  That's got to be a configurable parameter.

                  Email has been sent to Viessman

                  Comment

                  • victorp1612
                    Automated Home Jr Member
                    • Jun 2016
                    • 24

                    #10
                    Originally posted by Norfolkboy View Post
                    Email has been sent to Viessman
                    Interested to hear their feedback as I have the same setup as you

                    Comment

                    • Norfolkboy
                      Automated Home Jr Member
                      • Nov 2016
                      • 43

                      #11
                      Originally posted by victorp1612 View Post
                      Interested to hear their feedback as I have the same setup as you
                      Hi, are you running overtherm as well?

                      Comment

                      • Norfolkboy
                        Automated Home Jr Member
                        • Nov 2016
                        • 43

                        #12
                        From Viessman :

                        The Europe market boilers do not have the facility to change the overrun time parameters.

                        Pump overrun on all Vitodens 100-W boilers is temperature controlled, and it is optional on the open vent version. It may be used or not as you see fit. The boiler is unlikely to be harmed if it is not connected.

                        Comment

                        • victorp1612
                          Automated Home Jr Member
                          • Jun 2016
                          • 24

                          #13
                          Originally posted by Norfolkboy View Post
                          Hi, are you running overtherm as well?
                          Yep , sorry I should have added that I'm using Opentherm with a Vitodens 100W. I have 9 Rads and the DHW kit on a S plan config - with a ABV installed.
                          I definitely see Opentherm modulating as when the heat demand is low , average temperature demand is 40 ( would need to check again ) with 1 bar on the burner output displayed on the boiler.
                          If the heat demand increases, so does burner output and water temp.
                          When DHW kicks in , it goes full blast - up to 80deg . Once the DHW time is over , it closes the valve on the cylinder and the boiler pump will then stop. It will however kick in again for a few seconds as the temperature rises. It usually does this 2 or 3 times over a 10 minute period until the boiler temp decreases.

                          Comment

                          • Norfolkboy
                            Automated Home Jr Member
                            • Nov 2016
                            • 43

                            #14
                            Originally posted by victorp1612 View Post
                            Yep , sorry I should have added that I'm using Opentherm with a Vitodens 100W. I have 9 Rads and the DHW kit on a S plan config - with a ABV installed.
                            I definitely see Opentherm modulating as when the heat demand is low , average temperature demand is 40 ( would need to check again ) with 1 bar on the burner output displayed on the boiler.
                            If the heat demand increases, so does burner output and water temp.
                            When DHW kicks in , it goes full blast - up to 80deg . Once the DHW time is over , it closes the valve on the cylinder and the boiler pump will then stop. It will however kick in again for a few seconds as the temperature rises. It usually does this 2 or 3 times over a 10 minute period until the boiler temp decreases.
                            Thaks for that, what is the lowest temp you have seen it modulate at, my system sounds indentical to yours but im see it modulate at 28-33C which seems too low, also viessman just told me -"I would not use Opentherm myself, it's a bit like fitting a BMW automatic gearbox to a Mercedes-Benz"

                            Comment

                            • victorp1612
                              Automated Home Jr Member
                              • Jun 2016
                              • 24

                              #15
                              Originally posted by Norfolkboy View Post
                              Thaks for that, what is the lowest temp you have seen it modulate at, my system sounds indentical to yours but im see it modulate at 28-33C which seems too low, also viessman just told me -"I would not use Opentherm myself, it's a bit like fitting a BMW automatic gearbox to a Mercedes-Benz"
                              I've been reading your other posts , looks like you're having a hard time with your set up ...
                              Just checked my boiler behavior : here's what I noticed.
                              Current heat demand is minimal - the system is maintaining the existing set points.
                              The boiler pump was running and temp was 35
                              It fluctuated up and around 35 and when it dropped to 31 , the burner fired up ( 1 bar on the output display ) for approx 15 secs until temp reached 46/48. The burner then stopped.
                              Within approx 5 mins ( didn't time it ) , the temp had dropped back to 31 and the same process repeated.

                              Comment

                              Working...
                              X