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Oil CH boiler - air in the supply pipe

Discussion in 'Plumbing and Central Heating' started by jso, 6 Feb 2019.

  1. jso

    jso

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    I cannot get my (admittedly ancient) Myson Velaire CH & HW boiler to run...and we've now been without heat for about a fortnight (the coldest fortnight for the system to fail!)

    The final section of the oil intake tube is transparent so I can see the air bubbles, but despite many many attempts to let the air out via the bleed valve on the top of the unit where the oil is taken in, the boiler just Locks Out. Sometimes even while I've got the bleed valve open.
    It's a tedious process as there's a time delay before the reset button operates again.

    Are there any shortcuts to this, or indeed overall solutions to the problem?
    Any thoughts on why there might be air bubbles in the supply in the first place?
    The oil is running freely, and there are no obvious leaks on the supply pipes (at least not on those that are visible)
     
  2. oilboffin

    oilboffin

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    Get a qualified engineer in and stop messing with it you've a chance to make it worse.Bob
     
  3. jso

    jso

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    Thanks. But, with all due respect to your expertise, I'm not really "messing with it" just by opening the bleed valve, am I? And I' curious as to how there's a chance I make it worse?

    And I am poised to get my local Heating Engineer in - just trying to do it myself if it's do-able. If it's likely that there's something more seriously wrong, of course I'll give him a call.
     
  4. jso

    jso

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    OK. It finally fired up.
     
  5. oilboffin

    oilboffin

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    If too much air goes through the pump it's like running dry and you'll goose the pump.Bob
     
  6. conny

    conny

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    Oilboffin, not trying to hijack this thread but I'm curious also how you get air bubbles in a supply pipe?
    My oil is gravity fed so there is no pump as far as I am aware to cause cavitation. Does the air problem only occur with pumped supplies? (I don't have a problem with mine)
     
  7. jso

    jso

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    A CH engineer arrived this morning to service our boiler, despite us not having confirmed our enquiry about the possibility of this being done, and making a firm booking. Since the boiler was up and running (and also therefore too hot for him to service, in terms of cleaning the baffles etc) I said no thank you, but did discuss recent problems with him. He suggested that the pump can, paradoxically, draw in air through the bleed valve (presumably if it's opened too much?) That's maybe why it locked out a couple of times while I was bleeding the supply. But this doesn't explain the air bubbles already in the fuel supply pipe - their existence obvious because it's a transparent tube. So, where does that air come from?
     
    Last edited: 8 Feb 2019
  8. Andy4444

    Andy4444

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    A non-tight Compression fitting on the oil line could cause it. A long oil run can also be a culprit with the oil being stretched and oxygen being released into the oil line.

    Do a search on “HRM Wallstar” oil boilers and there’s a wealth of information in there about this issue.

    How many times have a I been somewhere and found a loose fitting where a DIYer has tried to “bleed” the oil line .
     
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  9. jso

    jso

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    Thanks for that.


    Ah. Maybe that's what Oilboffin Bob was getting at, not wanting me to "mess" with the system. But I just restricted myself to opening the bleed valve!
    OTOH I am about to tinker with the supply to the Aga...after reading various bits of advice on here and elsewhere.
     
  10. oilhead

    oilhead

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    Now the fun starts. Your Aga will have a purely gravity feed to the float control. If it is sometime since the Aga has been serviced, you will probably find that the burner feed will have carboned up and dried out. You will never re-establish the capillary without decoking it. Just remember, on Aga's, the most trouble is created by the nut on the end of the screwdriver!!!!!
     
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  11. jso

    jso

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    Yes, thanks for that. I'm OK with decoking the oil chamber in the burner, wick channels, bundy pipe etc - done it lots of times. But this time it's still not burning right, and it seems that there's inadequate fuel flow to the float control. Have ordered a new filter element for the inline filter, which was corroded and full of crud. Should arrive Saturday, so I'll have another play with it all then.
     
  12. oilboffin

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    Best of luck.Bob
     
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  13. jso

    jso

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    Thanks. Inlet and outlet also full of grot. Shank of screw that holds the filter housing toegther also rusty. Suggests water had accumulated in the filter?
     
    Last edited: 9 Feb 2019
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