Pumping air into combi expansion vessel - how many PSI?

Discussion in 'UK DIY' started by Dave£, Oct 24, 2004.

  1. Dave£

    Dave£ Guest

    I checked the air pressure in my Britony 80 combi boiler's expansion
    vessel the other day; that's after I lowered the water pressure to
    about 0.8 bar. There was no air pressure at all - as I suspected.

    I now need to know how many psi of air to pump into it when the water
    presure is, say, about 0.8 bar. I'm asking for a psi figure because my
    air pressure guage only has psi reading no bar reading.

    The expension vessel was originally pre-charged to 0.7 bar according
    to the manual.

    Thank you

    Dave L
     
    Dave£, Oct 24, 2004
    #1
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  2. Dave£

    Set Square Guest

    In an earlier contribution to this discussion,
    Dave£ <> wrote:

    > I checked the air pressure in my Britony 80 combi boiler's expansion
    > vessel the other day; that's after I lowered the water pressure to
    > about 0.8 bar. There was no air pressure at all - as I suspected.
    >
    > I now need to know how many psi of air to pump into it when the water
    > presure is, say, about 0.8 bar. I'm asking for a psi figure because my
    > air pressure guage only has psi reading no bar reading.
    >
    > The expension vessel was originally pre-charged to 0.7 bar according
    > to the manual.
    >
    > Thank you
    >
    > Dave L


    1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
    be exact - but I doubt whether your pressure gauge measures fractions of a
    psi]

    --
    Cheers,
    Set Square
    ______
    Please reply to newsgroup. Reply address is invalid.
     
    Set Square, Oct 24, 2004
    #2
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  3. Dave£

    Dave£ Guest

    On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square" <>
    wrote:

    >>In an earlier contribution to this discussion,
    >>Dave£ <> wrote:
    >>
    >>> I checked the air pressure in my Britony 80 combi boiler's expansion
    >>> vessel the other day; that's after I lowered the water pressure to
    >>> about 0.8 bar. There was no air pressure at all - as I suspected.
    >>>
    >>> I now need to know how many psi of air to pump into it when the water
    >>> presure is, say, about 0.8 bar. I'm asking for a psi figure because my
    >>> air pressure guage only has psi reading no bar reading.
    >>>
    >>> The expension vessel was originally pre-charged to 0.7 bar according
    >>> to the manual.
    >>>
    >>> Thank you
    >>>
    >>> Dave L

    >>
    >>1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
    >>be exact - but I doubt whether your pressure gauge measures fractions of a
    >>psi]


    SS, Thank you for your help again. One thing I'm not clear about: At
    what pressure should the heating system water be when I pump the
    expansion vessel to 10psi? And, should the boiler be tuned on or off
    during this operation?

    Dave L
     
    Dave£, Oct 25, 2004
    #3
  4. Dave£

    Set Square Guest

    In an earlier contribution to this discussion,
    Dave£ <> wrote:

    > On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square" <>
    > wrote:
    >
    >>> 1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi
    >>> [10.15 to be exact - but I doubt whether your pressure gauge
    >>> measures fractions of a psi]


    >
    > SS, Thank you for your help again. One thing I'm not clear about: At
    > what pressure should the heating system water be when I pump the
    > expansion vessel to 10psi? And, should the boiler be tuned on or off
    > during this operation?
    >
    > Dave L


    You must pump up the pressure vessel with the heating system cold and
    un-pressurised. At this point, the pressure vessel will be completely filled
    with air at 0.7 bar. *Then* use the filling loop to pressurise the system to
    around 1 bar, cold. *Some* water will enter the pressure vessel (on the wet
    side of the diaphragm), and will compress the air a bit more - but still
    leave plenty of expansion potential. When the system is hot, it shouldn't
    get to much more than 2 bar if everything is working correctly.
    --
    Cheers,
    Set Square
    ______
    Please reply to newsgroup. Reply address is invalid.
     
    Set Square, Oct 25, 2004
    #4
  5. Dave£

    Ed Sirett Guest

    On Mon, 25 Oct 2004 09:30:47 +0000, Dave£ wrote:

    > On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square" <>
    > wrote:
    >
    >>>In an earlier contribution to this discussion,
    >>>Dave£ <> wrote:
    >>>
    >>>> I checked the air pressure in my Britony 80 combi boiler's expansion
    >>>> vessel the other day; that's after I lowered the water pressure to
    >>>> about 0.8 bar. There was no air pressure at all - as I suspected.
    >>>>
    >>>> I now need to know how many psi of air to pump into it when the water
    >>>> presure is, say, about 0.8 bar. I'm asking for a psi figure because my
    >>>> air pressure guage only has psi reading no bar reading.
    >>>>
    >>>> The expension vessel was originally pre-charged to 0.7 bar according
    >>>> to the manual.
    >>>>
    >>>> Thank you
    >>>>
    >>>> Dave L
    >>>
    >>>1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
    >>>be exact - but I doubt whether your pressure gauge measures fractions of a
    >>>psi]

    >
    > SS, Thank you for your help again. One thing I'm not clear about: At
    > what pressure should the heating system water be when I pump the
    > expansion vessel to 10psi? And, should the boiler be tuned on or off
    > during this operation?
    >


    The FAQ may help (if it's read).


    --
    Ed Sirett - Property maintainer and registered gas fitter.
    The FAQ for uk.diy is at www.diyfaq.org.uk
    Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
    Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
     
    Ed Sirett, Oct 25, 2004
    #5
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