Grant Combi air lock (water)

Discussion in 'Plumbers' Talk' started by soabar, Sep 10, 2019.

  1. soabar

    soabar Member

    I've got a Grant Combi 90 Mk2 external boiler which I've just replaced the heat exchanger & PRV on - all went well, the radiators have filled without any issue, but on 1st run the overheat stat has kicked in & the PRV opened.

    As there are no specific instruction on filling other than a quick drain of the pump, I'm assuming that the auto air valve takes care of the boiler itself & a faulty one would leave air in the boiler? I did notice that the vale appeared a bit s****ed up when I was changing the PRV.
     
  2. Heat

    Heat Well-Known Member

    I wouldn’t trust the auto vents.
    Generally I replace them, although manual vents would be more sensible if care was taken on drain and refill.
    Check the control stat probe is inside the probe pocket in case you dislodged it.
    The boiler expansion vessel would also need checked - needs done once a year
     
  3. heatyman

    heatyman Well-Known Member

    Have you checked the pump is running? Otherwise, just keep bleeding, feeling the pipes in the boiler to identify the location of any airlock.
     
  4. soabar

    soabar Member

    Thanks for the replies.

    After what seemed like an eon of lifting the pressure, shuffling about radiators & bleeding via the pump - all good.

    I'm assuming it's the knacked auto air vent that made it such a s*** to bleed the boiler itself?
     

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