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Two pipe Air vented system

SteveSteve Member Posts: 486
Looked at one of these Friday night

Must be an early one, the returns are all dry

I have all of Dan's books just wondering if there's any more reading material Available

I want to fully understand this before I start

Steam seems to come up the return first

Boiler has been replaced about five years ago

Vents appear to be way undersized


  • SteveSteve Member Posts: 486
    edited February 2013
  • Paul48Paul48 Member Posts: 4,231
    edited February 2013

    I read an article about 2 pipe vented systems in the last couple days. I didn't save it, and can't find it again. Damn, I hate that! The only thing I remember is, it was developed for larger systems. To avoid sewer main sized pipes they would have to run to allow for the counterflow in a single pipe.
  • ttekushanttekushan Member Posts: 901
    I've worked with several of these systems.

    I've worked with several of these systems.

    The returns are usually dry until the boiler room. The returns can fill with steam, but really shouldn't until a little later in the cycle.

    Some things to remember about these:

    The returns must NOT be vented;

    The main usually isn't vented in my experience, but if so, its drip must be isolated from the return thru a water seal or float trap (NOT a float & thermostatic);

    The pressure must be low, like no more than 1 lb or so.

    If the returns are vented, plug the vents. If they drop into a vented condensate receiver, then you must trap the return with a float trap (again, no venting!) or a fairly low false water line. [I've plugged the thermostatic element on F&T traps in this situation with great results. But you didn't hear it from me! ;-) ]

    Just look for thermostatic air vent traps that will either "short circuit" the steam into the returns or vents on the return system. Keep the pressure low and you should be good to go. These systems work fine when treated right!
  • SteveSteve Member Posts: 486
    edited February 2013

    Guys thats a great help

    Any comments on the boiler piping
  • JStarJStar Member Posts: 2,668

    It's awful.

    Everything you shouldn't do is displayed there. Welded pipe, low header, bullheaded tees...
    - Joe Starosielec
    [email protected]
  • SteamheadSteamhead Member Posts: 11,327
    Is this

    a 2-pipe air-vent system that was designed that way, or a Vapor system that was knuckleheaded by someone putting radiator vents on it?

    A real 2-pipe air-vent system will generally have hand valves on both the supply and return radiator connections.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • SteveSteve Member Posts: 486
    It was definitely an original

    2 Pipe air vented system With dry returns

    I know the boiler pipping is bad But this should not cause steam in the returns, steam should Favor larger pipes, (the supplies) At least that is my understanding

    At least one apartment has been knuckleheaded steam traps installed and air vents removed

    I'm waiting to get access to the remainder of the basement and some other apartments before we do any work

    Thanks again guys
  • SteveSteve Member Posts: 486
    Getting full access on Thursday

    I will follow ttekushans Advice Hopefully we can get this sorted out

    Any other thoughts would be greatly appreciated

  • SteveSteve Member Posts: 486

    I found three areas where steam can shot circuit between supply and return

    The thing is some of it looks original is there any possible reason for this it makes no sense to me

    Just want to be sure before I drop them below the Water line
This discussion has been closed.


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