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Thread: Evohome TPI and pump overrun

  1. #1
    Automated Home Jr Member
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    May 2021
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    Default Evohome TPI and pump overrun

    Been doing a bit of reading about TPI. Currently when my old roomstat turns off the boiler after CH demand is satisfied my pump shuts down immediately and there is no overrun.

    When I replace the roomstat with a BDR91 to close the heating relay, if Evohome starts using TPI to reduce demand, will I need to add pump overrun? I'm assuming the pump live wire from the boiler simply hasn't been wired in (assuming the boiler supports overrun, it's a Viessmann Vitodens 100 WB1B open vent boiler)?

  2. #2
    Automated Home Legend
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    It could easily be that the pump over run time has been set to 0, at the boiler

  3. #3
    Automated Home Jr Member
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    Quote Originally Posted by bruce_miranda View Post
    It could easily be that the pump over run time has been set to 0, at the boiler
    I don't think there's any settings to change it, there's not much you can do with the controls on the front panel. However I have found what looks like an extra jumper in the Viessmann wiring instructions, looks like the pump can be wired into this, but will require an extra cable to be run from the airing cupboard down to the boiler.

    Image 366.jpg

  4. #4
    Automated Home Legend
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    If the boiler can drive the pump, then surely there must be a setting related to it. Unless the boiler is clever enough to detect that it's not got a pump connected and so hides that setting

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