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Oil boiler rising pressure

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  • 24-12-2019 2:49am
    #1
    Fred 2019
    Registered Users Posts: 1 ✭


    Hi - I'm new to this forum but maybe you can help with this one. The pressure relief valve on my oil boiler was leaking/releasing pressure from the oil boiler.  I simply unscrewed it and replace with a new one.  The new one has a pressure gauge built into it and shows the pressure building up towards 3 bar when heating is on.  I've manually  released the excess pressure via the valve back down to 1 or 1.2 bar approx to deal with it and released pressure from the expansion tank thinking this would help but it still continues to rise. I filled the expansion tank with air and drained off the excess pressure in the system via the pressure release valve on the boiler but still it continues to rise towards 3 bar when the heating is on for over a couple of hours. Any pointers would be welcome at this stage.


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    #2
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,218 Mod ✭✭✭✭Wearb


    Too little or too much air in the expansion tank would be a possibility.

    Filling loop letting water through rising the pressure on the system.

    A cylinder coil leaking if pressurized hot water cylinder.

    New radiators added without increasing the vessel size.

    Please follow site and charter rules. "Resistance is futile"



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    #3
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    How many rads? volume of EV?

    Cold Boiler
    With NO pressure on water side of expansion vessel, pre pressurise (air side) EV to 0.7/1.0 bar, then use filling valve (water) to pressurise to 1.3/1.5 bar then shut off the filling valve(s). The pressure should then not rise by more than 0.5 bar to 1.0 bar, if it does then the EV is too small for your system, a 12 litre will normally deal with most situations, up to 100 litres system volume easily.
    Also remember some condensing boilers like grant now have their PRV set to 2.5 bar (3.0 bar previously)

    If you have a unvented HW system, its possible that the coil may be split/holed and that your primary system is being pressurised from here,

    Just saw Wearb's post now.


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