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Air in boiler system

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jstratz
jstratz Member Posts: 10
I few winters ago I installed a Weil McLain Gold oil boiler in parallel with a wood boiler in my basement with some used cast iron radiators we pulled from a job. I have each of the radiators home run with 1/2” Roth O2 barrier pex. I do not have an automatic fill on the system and I have no automatic air purger. The theory being that I can just vent the air out the radiators. It has been three winters now with no new water needing to be added and I still wake up sometimes in the middle of the night to giant slugs of air gurgling through my radiator valves. O2 barrier not working properly? Or is it normal without an air purger for air to migrate around a bit amongst the radiators without ever really being able to get all of it?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,668
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    I'd say it was normal. The air will collect... somewhere... and when there gets to be a big enough bubble it will burp.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • DZoro
    DZoro Member Posts: 1,048
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    It would make your life easier if you install a automatic feeder, and a good air purger.
    D
  • HVACNUT
    HVACNUT Member Posts: 5,893
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    What type of expansion tank is on the system?
    STEVEusaPA
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    HVACNUT said:

    What type of expansion tank is on the system?

    And is it big enough?

    How's it piped? Pumping away? Pics.

    There was an error rendering this rich post.

  • jstratz
    jstratz Member Posts: 10
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    I have two #30 tanks. I’m down there often building a fire so I always monitor the pressure. Never has strayed below 12 psi. If I get rid of the wood I may add an Autofill then. It just seems odd to me that I will purge air from the radiator every week and get a significant amount out sometimes, and then a while later I will get another large slug of air. If it’s hiding in the system it seems that there must be a very cavity somewhere or else the O2 barrier pex isn’t very quality
  • jstratz
    jstratz Member Posts: 10
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    We have a used Spirovent sitting on the shelf at the shop I have thought about putting on but the issue hasn’t bothered me too much yet. Just was curious if the radiator tops could hold that much air commonly to where I would still be bleeding 3 Heating seasons later or if this is more of an issue with the Pex
  • DZoro
    DZoro Member Posts: 1,048
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    Pex is not the problem, proper installation with air venting and automatic feed. There's a reason for each, and that is what you are experiencing, the results of not having them.
    Yes one can get by without, but especially with a wood boiler over firing / boiling can certainly cause issues.
    D
  • jstratz
    jstratz Member Posts: 10
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    I can completely get behind having them as part of a proper setup and we install them on every customers system. I’m more curious on the why. I figured I will always be messing with my own system so I shouldn’t need it. Especially with having cast iron radiators. I figured any air would quickly get into them and get purged within the first week. I have a pressurized wood boiler setup with a proper over temp aquastat that limits the water temp to 200 degrees max. If it gets that hot I have it tied into TT on the boiler to kick on the pump and “heat dump” into the house so it never boils and isn’t open to atmosphere. I am just lacking in experience on typical older cast iron systems. We don’t have many in our small town. It’s a sealed system and my thoughts are that it should need a few purges in the beginning but then run smooth. But many large air pockets over three years seems odd.