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Reason for being air bound?

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john p_2
john p_2 Member Posts: 367
in Gas Heating
Have a friend who has a steam boiler with a loop of hot water baseboard piped off of it for the second floor that was recently renovated.

He maintains the boiler as best he can and shut the boiler down, isolated the baseboard loop and drained and flushed the near boiler piping. Not sure if he ever added cleaner or not but when he started the system back up the baseboard loop was air bound - couldn't get any circulation. What would cause this and what should / could be done to eliminate the issue?




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  • Jamie Hall
    Jamie Hall Member Posts: 23,280
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    Do I assume that at one point this arrangement did work properly? The problem is that the piping for the second floor is under a rather high vacuum when the pump isn't running, and even when it is, it is under a fair amount of vacuum. If there is air got in there, the pump has to operate under the full gravity head plus the circulating head, instead of just the circulating head, to get the water up and over -- and that may be more pressure than the pump is able to provide, or at least at which it can provide any significant flow.

    If there are no leaks and you have a way to run water through it -- say from the domestic supply -- under enough pressure to get it to really flow, you may be able to get the pipes sufficiently free of air to work...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • john p_2
    john p_2 Member Posts: 367
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    I believe he tried putting a hose from city water on the drain (hose bib) of the system side of baseboard loop (S) and open the other hose bib (R) with no luck of circulating water...
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,519
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    This method is described in Dan's book. I think it's in the "How Come" book. You have to fill the baseboard system with water (using hoses and city water) with the boiler and circulator off and make sure it is completely vented. Once you get it filled and vented open the valves to the boiler and turn on the circulator
  • Jamie Hall
    Jamie Hall Member Posts: 23,280
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    john p said:

    I believe he tried putting a hose from city water on the drain (hose bib) of the system side of baseboard loop (S) and open the other hose bib (R) with no luck of circulating water...

    If he didn't get water flowing with city water pressure it's not air. Something else is blocking the flow.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,519
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    @Jamie Hall could be anything but they may not understand how to fill the system
  • Fred
    Fred Member Posts: 8,542
    edited March 2017
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    In his second picture it looks like the line that is labeled as "Hot water supply to Baseboards" has a valve on it that is valved off (blue handle) Is that the problem?
    Looks like the Return (blue handle) is valved off also???
  • john p_2
    john p_2 Member Posts: 367
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    First let me say I was not present during any of the issues or attampts to fill. I would know to open a closed valve....That said I should tell you he finally did get it to fill and work properly once again.

    I don't care for using the ball valve where I labeled "tempering valve"...What kind of valve would be correct to use instead?
  • Fred
    Fred Member Posts: 8,542
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    john p said:

    First let me say I was not present during any of the issues or attampts to fill. I would know to open a closed valve....That said I should tell you he finally did get it to fill and work properly once again.



    I don't care for using the ball valve where I labeled "tempering valve"...What kind of valve would be correct to use instead?

    I certainly didn't mean to offend you. My apologies if I did. I was just looking through the pictures for any clues and noticed those valves were closed.
  • john p_2
    john p_2 Member Posts: 367
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    Not offended just letting you guys know I'm a bit sharper than that, lol.
    My buddy just told me the closed blue handled valve was closed when he was filling the system.
  • Jamie Hall
    Jamie Hall Member Posts: 23,280
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    john p said:

    Not offended just letting you guys know I'm a bit sharper than that, lol.

    My buddy just told me the closed blue handled valve was closed when he was filling the system.

    I doubt that we would notice such things -- had we not all done the same kind of thing at least once over the years! Glad they got it working again.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • john p_2
    john p_2 Member Posts: 367
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    What about the correct type of valve for "tempering" the water? He also mentioned the flow control valves chattering during initial fillings....Assuming this is caused by trapped air?!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,519
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    That is the correct valve. Read the description in Dan's book. You have to understand how this type of system works. The tempering valve keeps the baseboard from getting too hot when the boiler water is 212 deg from steaming.
  • Steamhead
    Steamhead Member Posts: 16,832
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    john p said:

    I don't care for using the ball valve where I labeled "tempering valve"...What kind of valve would be correct to use instead?

    An ordinary stop-and-waste valve should work. You don't need the full-flow capability of a ball valve in that location. And the S&W is much easier to fine-tune than a ball valve.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • arpitkakkar1
    arpitkakkar1 Member Posts: 3
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    The reason behind air bound is the valve is not properly closed. proper lab equipments to be used in the labs like bacteriological incubator it can safe from big mistake.
    glass bead sterilizers

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