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Combi seems to be running with no demand...

Discussion in 'Plumbing and Central Heating' started by charliegolf, 25 Jul 2017.

  1. charliegolf

    charliegolf

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    My Worcester Greenstar seems to be 'burning' for a layman's term, with no demand. Heating is off, so only the water side is on. When I demand hot water, it certainly 'kicks in'- seems to ignite and is louder. But there is a sense that it's using gas when no demand is there...

    Any advice? Thanks.

    CG
     
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  3. muggles

    muggles

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    Could have a hot water preheat enabled. What model is it?
     
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  4. Agile

    Agile

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    If it were really firing up then the heat would have to go somewhere and so something would be getting hot.

    Also you would be able to feel warm gases expelled from the flue!

    Do you have these symptoms?
     
  5. charliegolf

    charliegolf

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    Agile, just saw this, will check. Thanks
     
  6. FiremanT

    FiremanT

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    Think the first thing you should do is respond to Mugs :rolleyes:
     
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  7. Steelmasons

    Steelmasons

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    Possibly the plate...:)
     
  8. charliegolf

    charliegolf

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    Muggles, apologies- it's a Greenstar 37 ish! Preheat is off, as far as I know. As for Agile's point- I've jad a housefull here today, so will check tomorrow.
     
  9. FiremanT

    FiremanT

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    We have made a lit if money over the years from folk who said "\......... (fill to suit), as far as I know"

    ;):)
     
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  11. McCombi

    McCombi

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    Eco light will be lit green if preheat is off. If it's not lit, push it for a few seconds to change it.
     
  12. charliegolf

    charliegolf

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    OK actual (not 'as far as I know':D) conditions now...

    No demands on the system for hot water; heating is OFF; Eco light is ON; the low 'rumble' continues from the boiler; and there are no discernable gases being expelled, warm or not.

    CG
     
  13. Agile

    Agile

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    So the boiler is not firing up!

    The low rumble would usually be the pump running. Easy for an engineer to check inside if this is the cause.

    I am not aware of any setting on that model which would make it run constantly, but perhaps Mr Combi could confirm.

    If not then there would seem to be a fault on the boiler. This can be caused by a sticking relay on the control PCB keeping the pump running. New PCBs are not so cheap!

    But of little relevance if it is not disturbing you. Could be left until the next annual service, or bring it forward be a few weeks.

    Tony
     
  14. McCombi

    McCombi

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    If it's a cdi model, had faulty pumps on them a few times where pump runs 24/7.

    Something to do with faulty pump internal pcb, not the main boilers pcb
     
  15. Agile

    Agile

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    Presumably this is in the last year or two's boiler with smart pumps fitted?

    So they have a permanent live to the pump?
     
  16. McCombi

    McCombi

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    No was about 4 years ago when I worked at worcester.

    The greenstar cdi combis (similar to the fans) have mains fed to them from board all the time to power them, even when there's no demand, but they shouldn't be spinning with no demand or overrun finished etc.


    It's the vdc separate wiring that controls the pump speed etc and activates them spinning.

    (My terminology may not be 100% accurate so apologies if not, but I know it's a fault I've had with these pumps 2 or 3 times that I can remember)
     
  17. Agile

    Agile

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    Right thanks.

    So it is a fully modulating pump then.

    Something that few makers seem to have been very keen on.

    Apart from Vaillant with their stepped modulation pump.
     
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