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Valliant F75 - no water outside - losing pressure

Discussion in 'Plumbing and Central Heating' started by leeovery, 11 Sep 2014.

  1. leeovery

    leeovery

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    Hi,

    Ive googled as much as I can but am now looking for some advice from somebody thats knowledgable in this area.

    My Valliant boiler as been showing the F75 error since we moved in about 6 months ago.

    About once every 7-10 days I have to recharge/repressure the system.

    From what I can see the system is losing pressure but there is no water outside at all from the discharge pipe.

    Does this automatically mean a leak somewhere or could it be something else?

    Im currently observing the gauges to see if the pressure climbs high before it drops.

    Ive had the exp vessel repressured today by a British Gas engineer but it failed again after about 4 hours!!

    Any help would be appreciated. Just trying to shortcut the fix time here. Not doing it myself but just trying to understand etc.

    Thanks!
    Lee

    EDIT: Wanted to add that I repressurised the system after it failed today back to 1.5BAR. With the heating running its now reading 2.3. Is this too high?

    Its quite a big house so maybe I need an additional exp.v?

    My main concern is either way, whether the system is over pressurised and then dumping, or if the system is just losing pressure, shouldn't I see the water escaping outside? Does this suggest a leak even if I need another expv?
     
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  3. lightning

    lightning

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    if your losing pressure you have a leak.

    top up boiler to 2 bar shut off iso valves underneath boiler {turn off boiler as well}

    leave over night, if pressure has gone down then you have a boiler issue, if not gone down open iso valves and if pressure goes down you have a leak on pipework or rads.

    Paul
     
  4. leeovery

    leeovery

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    Thank you. I'll try that tonight.

    The digital gauge is now ready 2.4. Is this night? 0.9 increase when running central heating?
     
  5. how many rads on the system?
     
  6. leeovery

    leeovery

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    3 separate systems:

    11 downstairs
    6 upstairs
    2 towel rails

    Currently running all 3 at once and boiler seems to be holding steady at 2.4, up from 1.5 cold.
     
  7. If you only have the expansion vessel thats in the boiler then it is most likely undersized with that kind of load on the system, which will lead to premature failure of the vessel and excessive pressure in the system that can cause leaks elsewhere such as spindals on rad valves, auto air vents ect.

    Did the british gas engineer drain the boiler and leave it open to atmosphere (drain off kept open) as he re-pressurised the vessel?
     
  8. leeovery

    leeovery

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    I believe so.

    He attached a pipe under the boiler and drained off.

    I remember him then starting the boiler up but quickly stopping and fastening the drain underneath. So suggests he pressurised with valve open...

    I didnt pay that much attention unfortunately.

    He's coming back tomorrow to have another look, hence this post. :)
     
  9. kidgreen61

    kidgreen61

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    +1
     
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  11. leeovery

    leeovery

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    Is this suggesting more than one problem here?

    Presumably if I was to add another EV I would still have the issue of the system losing pressure?

    Bottom line - if the system is losing pressure and there is no water being dumped outside - I have a leak in the house somewhere. Is that correct???

    I just tried to shut off the valves under the boiler to do the overnight test as instructed above but unfortunately there is no permanent live to the display so I cant see the pressure, other than with the stupid little analogue gauge - which seems pretty useless to me...
     
  12. Bunnyman

    Bunnyman

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    If there's no permanent live it's wired wrong, that needs sortin as well as u have no pump overun
     
  13. The831Bunny

    The831Bunny

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    I'd install an additional 10L expansion vessel on the return close to the boiler, make sure the boiler vessel is not pressurised over 1 bar, replace the pressure sensor, and get the boiler rewired correctly by a Gas Safe engineer who knows what he's doing!
     
  14. leeovery

    leeovery

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    Ill mention this to the British Gas guy thats coming round. We have homecare so dont really want to pay someone else if I can avoid it. Wouldnt know who to call anyway to be honest - it always feels like potluck if you get someone who knows their stuff or not.

    If I replace all the above and add a new 10L ev, would that stop the pressure drops? Im guessing not.
     
  15. The831Bunny

    The831Bunny

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    Irrespective of the possible system leak, the vessel and wiring only bring the system up to standard as a minimum. The pressure sensor is a no brainier if you've been having F.75 problems and it's original. Did BG install the system?
     
  16. leeovery

    leeovery

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    I'm not 100% sure. I think so.

    We've only been here since March this year.

    I'll explain all this when he arrives later.

    Thanks for your help!
     
  17. Agile

    Agile

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    Really it surprises me when a national Company's employees are not understanding the system and explaining it to the customers!
     
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