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air in oil line

Pin Member Posts: 61
Recently I been experiencing a weird problem with my oil burner. Whenever the oil tank has approximately 1/4 left, the oil line will get air inside the line between heat cycles. I will have to bleed the air out in order for it to fire. Once the thermostat is satisfied, the boiler shuts off and the next time the thermostat calls for heat, I have to go and bleed again.

This does not happen when I have more oil in the tank. What could be the problem?



  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    pin hole

    If the line enters the tank from the top, it could have a pin hole in it down low that's letting the air in. If that's the case you need to replace that piece of line. I suppose it could also be an air leak down the line too, though I'd think that would show up as an oil leak during the off cycle.
  • conway
    conway Member Posts: 7
    same problem

    I have the same problem it seems - I have had this happen a couple of times in the past few days, after the oil reached about 1/4. (Getting filled today - will see if it fixes the problem).

    But my line enters the tank on the bottom, not on top. And I'm pretty sure I don't have an oil leak - my tank is in the basement above ground, and I would smell it if it's leaking.

    Are you saying the line is leaking, or the tank?
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    not the tank

    If the line comes into the top there can be a pin hole in the line that lets air in once the oil drops to that point. Guess that's not you situation. It may seem obvious, but if air is getting into the line then ... you must have air leaking in :)

    Is the tank situated below the oil burner? Is there an oil safety valve?

    Have the filters been checked lately?
  • conway
    conway Member Posts: 7
    more details

    The tank is above the burner, but the oil line (single line) goes up to the ceiling and crosses the basement (about 35ft) until it drops back down to the boiler.

    There is a safety valve at the tank.

    I checked the big filter - the 1A-25A General filter, and it looked ok. (To my untrained eye). The filter was changed at the beginning of the season.

    I didn't check the filter internal to the pump.

    I actually had the same sort of thing happen at the beginning of the season - every time there was air in the line - but the tank was almost full then. I tracked that problem down to the fact that there was a tech in to tune up the system over the summer, and I think he didn't align the gasket on the General filter well. When I opened the filter and re-sealed it the problems went away. I tried this trick this time again, but it didn't help.
  • Air

    Ahh, overhead lines.  You need an oil de-aerator-commonly called a Tiger Loop.  I would first have your technician check for a vacuum leak, then if all is okay install a Tiger Loop.  Good Luck
  • conway
    conway Member Posts: 7

    Thanks guys for your replies!

    So does it make sense that without a 'tiger loop' you'd get air in the system when the oil is low?
  • Coany
    Coany Member Posts: 91
    you need to vacume prime

     close the firomatic at the tank and start the burner

     wait 5 seconds or so and open the bleeder, until it locks out

     quickly close the bleeder before the burner stops spinning completely

    reset the lock out and start the burner, open the bleeder

     hurry over to the tank and open the firomatic at the tank.

    You should hear the high vacum in the line sucking the oil out of the tank.

    hurry back over to the burner and close the bleeder port once you get pure oil /no foam.

     this will force every bit of air trapped in the line out the bleeder port.

     its a great practice every time you prime an overhead line.
    " Do what you can, with what you have, where you are" Teddy Roosevelt
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