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Should pump overrun happen every time boiler switches off (Potterton Profile 80e)?

Discussion in 'Plumbing and Central Heating' started by Spiderpig, 18 Oct 2019.

  1. stem

    stem

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    The pump overrun on the Potterton 80e is thermostatically operated. It will only run if the temperature of the water is in excess of 80 degrees C.

    So, from what you say it may be faulty. When the boiler is set at a low temperature, ie less than 80 degrees, all is well, yet when you run it at a higher setting the overheat trips which suggests the overrun is not operating as it should.
     
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  3. ianmcd

    ianmcd

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    or it is operating as it should and you have a restriction somewhere and the boiler thermostat is not cutting in when it should (more likely)
     
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  4. stem

    stem

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    Apologies, I misunderstood. I thought the OP meant that the overrun wasn't operating, in that the pump stopped as soon as the boiler shut down, not that it kept running but the overheat still tripped.
     
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  5. ianmcd

    ianmcd

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    @stem the Op hasnt answered when I asked if he had fully pumped or gravity HW set up as this boiler has a slider that tells the boiler what the set up is as the over run thermostats are different
     
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  6. dilalio

    dilalio

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    I was being facetious :p
    There are many on here who would worry about it ;)
     
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  7. dilalio

    dilalio

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    Screenshot_20191020_131842.jpg
     
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  8. Spiderpig

    Spiderpig

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    Hello, thanks for all the helpful replies. Yes, it is a fully pumped system. There is only one 3-core cable between the boiler and pump, which is correct per boiler installation instructions. As the pump does work (just no overrun function) I suppose that would point to the boiler's overrun thermostat being faulty. It's not an expensive part so will probably try replacing that first.
     
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  9. ianmcd

    ianmcd

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    it is not the cable to the pump that is important, the cable supplying the boiler needs to be 4 core, L,N,E and switched live
     
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  11. vulcancontinental

    vulcancontinental

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    ?
     
  12. Spiderpig

    Spiderpig

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    Sorry, I'm not sure what you mean by this. The pump is only controlled by the boiler which has an in-built, thermostatic overrun feature.

    In a dramatic turn of events, after remaking the electrical connections to the overrun module and some gentle percussive persuasion to it I do now have pump overrun, possibly for the first time in years! Just noticed that this morning. So could be all good or if it stops again then a replacement module will indeed be the fix (y).
     
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  13. ianmcd

    ianmcd

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    when a boiler has a pump o/run then the boiler needs a permanent live supply in order for the o/run to work when the switched live is switched off, too many boilers are installed with this permanent live missing, yours is OK though if it is now working
     
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  14. stem

    stem

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    @ianmcd is quite correct. The pump requires L, N & E connections when connected to systems with or without pump overrun. However the boiler requires a 4 core cable because as well as the permanent L, N, & E it will also have a second Switched Live from the controls telling it to run.

    Sometimes; usually when an older boiler that didn't have a pump overrun is replaced with one that does, there isn't a permanent live present, only the switched live from the controls. In such cases when the external controls turn the switched live off, there isn't any power to keep the pump overrun working.

    However, as you have now managed to get the pump overrun working the permanent live must be present.
     
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  15. Spiderpig

    Spiderpig

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    Ok, I see how that works now. Thanks very much for the explanations.
     
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  16. Mottie

    Mottie

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    Yes, my old Potterton had a 3 core and earth going to it and a 3 core coming out and going to the pump.
     
  17. vulcancontinental

    vulcancontinental

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    Which of the 4 cables powers the pump? Are you not missing one, the pump is elsewhere.
     
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