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Valiant Ecotec plus 831 pressure issue

Discussion in 'Plumbing and Central Heating' started by chieflasagnaeater, 31 Dec 2014.

  1. chieflasagnaeater

    chieflasagnaeater

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    Hi,

    My boilers symptom is it's normal operating pressure, to ignite, is about 2 bar which is middle of the grey on the gauge. Once fired it increases to some 2.8 bar. (The Valiant eng has set CH temp to high as I have a Rf thermostat.)
    Have just drained the system and repressurised the EV to 1 bar but this has not helped. Is there anything obvious to check before getting an engineer in.
    PS. Had it serviced in August. In Sep drained and refilled to fit a new kitchen rad and it seems since then it has not been right.

    Thanks,
    CLE
     
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  3. The831Bunny

    The831Bunny

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    The cold fill system pressure should only be 1.0 - 1.5 Bar maximum. If you have a large volume system (approx 12+ radiators or above) you may need to add an additional expansion vessel to the system.

    All things equal a sealed system should rise a maximum of 0.5 Bar from cold to operating temperature. Less is preferable. If this is the case on your system and the expansion vessel is charged correctly, you need an additional vessel.

    Also a reminder that removing the front casing of the boiler, even to check the vessel, is beyond the gas safety regulations scope of a DIYer I'm afraid.
     
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  4. ALCPlumbing

    ALCPlumbing

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    Unless the pressure is going through the roof and dispersing water through the PRV then I wouldn't really consider it a problem. As stated you possibly need a larger vessel so may have to add an additional one external to the boiler but if it's all working why are you even worried?
     
  5. chieflasagnaeater

    chieflasagnaeater

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    You make a good point about the system cold fill pressure ideally 1-1.5bar because at that level my gauge is only just off zero....presume the gauge could be faulty!

    I have 4 rads and 2 hydronic plinth heaters downstairs and 4 rads upstairs so would think the internal expansion vessel is sufficient.

    ALCPlumbing, to expand on the problem I have, I get F75 fault if the cold pressure is below 2.0 bar and then when heating is on full whack it often auto cuts out if the pressure goes above 3 bar.
     
  6. Terry lambert

    Terry lambert

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    theyre are a few things that can cause F75. Any competent engineer should be able to fix this.

    It's at the crux of your problem
     
  7. Tipper

    Tipper

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    If you check the pressure as read by the pcb by pressing the bottom left button on the control panel you can see just how useless the pressure gauge is.
     
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  9. The831Bunny

    The831Bunny

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    ...or the pressure sensor ;)
     
  10. Bunnyman

    Bunnyman

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    The gauge is more likely right with the symptoms u describe
     
  11. chieflasagnaeater

    chieflasagnaeater

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    I have had the pressure sensor replaced. The digital readings are now lower and look more realistic....low grey reads approx 1 bar.
    However, the pressure still increases from 1 to about 2.6 bar with CH and DHW demand.
     
  12. Dan Robinson

    Dan Robinson

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    Expansion vessel needs checking /charging
     
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  13. chieflasagnaeater

    chieflasagnaeater

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    Thanks Dan, will give that a go this weekend.

    With the system drained, EV pressure should be at 3/4 to 1 bar right?
     
  14. chieflasagnaeater

    chieflasagnaeater

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    The EV was at 1.6bar. Repressurised to 0.7 and all now seems fine.

    ...thanks!
     
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