Help with Evohome / Opentherm / Intergas

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  • mylesm
    Automated Home Guru
    • Nov 2015
    • 153

    My Pump Over run is only 4 mins but I think its a feature of Opentherm that it circulates much cooler water almost continually so pump runs all the time

    Comment

    • mtmcgavock
      Automated Home Legend
      • Mar 2017
      • 507

      Originally posted by bruce_miranda View Post
      What is your pump over run time set to? On my Vaillant, I have it to 20 mins, this means that the pump could easily be running for the duration of the heating cycle, because the 20 mins is deliberately long enough to help circulate the already warmed up water.
      Out of interest, why have a 20 minute pump over run? Surely as you say this means you pump is running for most of your heating schedule, but once all your HR92s are closed down the boiler will just pump it around the bypass.

      Comment

      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        It allows the boiler to cool down gradually and in theory helps the heat exchanger. In practice it also continues to heat up my towel rails that don't have any TRVs on them.

        Do you have any means to monitor what temperature is being requested by OT off the boiler. On my Vaillant, any temperature request more than 10C is effectively a heat demand. So even 28C would be treated as a Heat Demand and would have caused the pump to stay on.
        Last edited by bruce_miranda; 8 September 2017, 06:53 PM.

        Comment

        • mylesm
          Automated Home Guru
          • Nov 2015
          • 153

          NO I have no means to monitor Temp Requested but it seems like my pump is running almost all the time with reduced Flow Temps maybe thats the way opentherm works it matches flow temp to equal heat loss so keeps boiler at low temp but pump of course runs

          Comment

          • Dan_Robinson
            Automated Home Ninja
            • Jun 2012
            • 347

            If there is a demand for heat, the pump will run. Simples.
            Kind Regards - Dan Robinson (Jennings Heating Ltd)

            Comment

            • mylesm
              Automated Home Guru
              • Nov 2015
              • 153

              Thanks Again Dan Just trying to get my head around OT it seems to run pump for extended periods at Low flow temp where BDR would Fire Boiler in Short Bursts to maintain Zone Temp As you Know I have Intergas Rapid which has internal pump I presume this Pump also modulates Its not very cold weather yet But OT is definitely controlling Zones at very stable Temp Will be interesting to see how it works in Depths of Winter.

              Comment

              • The EVOHOME Shop
                Site Sponsor
                • Dec 2014
                • 483

                Originally posted by mylesm View Post
                Thanks Again Dan Just trying to get my head around OT it seems to run pump for extended periods at Low flow temp where BDR would Fire Boiler in Short Bursts to maintain Zone Temp As you Know I have Intergas Rapid which has internal pump I presume this Pump also modulates Its not very cold weather yet But OT is definitely controlling Zones at very stable Temp Will be interesting to see how it works in Depths of Winter.
                Yep, as Dan states this is how the system works with OpenTherm. The pump does indeed modulate between the installers set values 3. and c. (hopefully he has set them?) depending on burner output.

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