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2 pipe radiator - please confirm and advise

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Is this radiator (see photo) a 2 pipe radiator and if so how does it work when we also have some 1 pipe radiators. 10 units are serviced by one boiler - steam heat. We have had one plumber say that even though there are 2 pipes, it is a 1 pipe system. Then we had 2 other plumbers say we have both a 1 pipe and a 2 pipe system. In order to get heat to all units, we need to know what exactly we have. Can someone help? I need to know before we hire another plumber and spend the winter with clanging pipes and no heat in some units.

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  • steam2pipe
    steam2pipe Member Posts: 59
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    PS Image is now attached below of the radiator.
  • mattmia2
    mattmia2 Member Posts: 9,662
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    It is..weird. It is 1 pipe because it has a vent, no idea why there would be 2 1 pipe pipes in to a radiator that small. Would have to look at where those pipes go and try to figure out why it is piped like that.
  • steam2pipe
    steam2pipe Member Posts: 59
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    I am asking this because one plumber told us that even though there are 2 pipes on each side, it is a 1 pipe system. Then others say it is a 2 pipe system with some 1 pipe radiators. It's confusing and something we need to clarify. Thanks for any help anyone can offer.
  • JohnNY
    JohnNY Member Posts: 3,230
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    It's a 2-pipe air vent system. They're out there.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
  • ttekushan_3
    ttekushan_3 Member Posts: 958
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    What JohnNY said. 
    Two pipe with air vent predates the thermostatic steam trap. It’s a nice system. Covered fully in Dan Hohohan’s The Lost Art of Steam Heating (highly recommended from the bookstore here) you might also search this site for further information. 

    Both valves have to be open for it to work. Take pictures of the boiler installation as it is now. A water line that’s lower than original can cause some trouble as can boiler pressure set too high. 

    These systems are just fine as long as you know what you’re looking at. 
    I have stewardship over two such systems, both in 1880’s churches. 
    terry
    JohnNYmattmia2Erin Holohan Haskell
  • steam2pipe
    steam2pipe Member Posts: 59
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    Thank you. Does a 2 pipe air vent system mean you can also have a 1 pipe radiator in some units of the condo using the same boiler?
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    edited October 2020
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    You can if they’re small. The point of two pipe operation is to take the condensate load off the steam main. Usually is all done the same way throughout. But who knows what circumstances informed those past decisions. 

    In one of the churches there are two zones, one two pipe with air vent (circa 1880) the other single pipe (the new 1915 part). 

    There’s always the possibility that the single pipe radiator(s) were added, moved, or ??.  Vice versa is unlikely I would think. It’s even possible it was built that way just to relieve the condensate flow on the largest or farthest radiators. If there’s more than one main steam line it might be divided up that way. 

    I have one client with a hybrid system with a two story house where each riser feeds two radiators: one on the 1st floor and the other on the 2nd directly above it. 1st floor rads are two pipe with air vent and the 2nd are single pipe. All on one riser! So the main is sized betweeen the two design standards and there’s a decidedly odd return arrangement. The system was added after construction owning to the age of the home. 

    Point is, anything is possible. But does it work, and when did it last work. 

    It’s really hard to get the big picture and conduct the fun forensics (well, I think it’s fun but I’m weird) on the system’s history with the info on hand. A real steam pro could probably straighten it out pretty quickly in the interests of both economy and comfort. 
    terry
    steam2pipe
  • Roddy
    Roddy Member Posts: 63
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    I have a one pipe parallel flow system that had been modified years ago by a knowledgeable previous home owner. In our kitchen, under a built in table (part of a kitchen booth set up) is the only cast iron base board heater/radiator in the house. All the rest are traditional cast iron radiators. Anyway, this baseboard does not have a vent and it has two pipes, one on each end. It heats great. I'm guessing the one pipe feeds the steam and the other pipe carries the steam to a small, traditional radiator in a nearby bathroom. I'm pretty sure this is not part of the original set up, but came years later.
    steam2pipe
  • Jamie Hall
    Jamie Hall Member Posts: 23,322
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    No reason at all why it won't work perfectly well. And yes, you can mix one pipe, two pipe air vent, and even two pipe standard all on one system. The only thing to consider really is how does air get out and how does condensate get back to the boiler. Tw pipe air vent is more like one pipe than it is like standard two pipe -- there are no true dry returns, for instance, and balancing it is a matter of venting, and the radiator inlet (and outlet) valves must be fully open.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    steam2pipe
  • steam2pipe
    steam2pipe Member Posts: 59
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    Thanks, everyone, for your comments. A plumber came today and said we have the '1 pipe/2pipe air vent' system as you said and that it acts as a 1 pipe system. He said we had bigger issues, though, because the boiler is piped improperly.
  • dopey27177
    dopey27177 Member Posts: 887
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    This radiator is two pipe radiator.
    Some very old steam systems were two pipe, Some were mixed with one pipe and two pipe connections.

    This system is a two pipe under the rules of one pipe steam.

    The steam pressure this system will operate best at is 1/2 psi burner on and one psi burner off.

    Jake

  • Lard
    Lard Member Posts: 115
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    The church I take care of has one-pipe and two-pipe air-vent radiators.  The purpose (as mentioned earlier) is to take condensate load off of the main.  There are two 237-EDR indirect Vento stacks in the floor along with two 63-EDR ceiling radiators in the basement piped as two-pipe air-vent.
    The Vento stacks were piped this way in 1916 due to the high condensate production, but the ceiling rads were a 1955 addition and totally wrong with hoffman 40 vents and F&T traps draining to the wet return/below the water line.

    The remaining 1537 EDR of radiation is all standard one-pipe. Once I removed the knucklehead F&T traps, all works wonderfully considering the hilariously oversized boiler. There is a bit of clanging caused by wet steam/bad near boiler piping to be fixed when this boiler bites it.


    Mixed systems work well.  Keep those valves wide-open and pressure as low as possible.  That said, Bad near-boiler piping or an unstable water line can cause any steam system to throw a tantrum.  Has the boiler ever been skimmed? Is there even a header or equalizer? Is the header or riser(s) a nice water-accelerating chunk of 1 1/2” (Maybe even copper!) pipe? Did they reduce the equalizer in the horizontal instead of the vertical? Do the mains tie into the header between risers? Is there a sag in the main causing water to block flow/hammer? Is a former wet return now above the water line? Boiler pictures from a decent wide angle will help the great people here diagnose the clanging/no-heat issue. If the plumber said the boiler piping is wrong, he may or may not know what he is talking about. At minimum it must match the diagram that is in every boiler’s installation manual!
    ethicalpaul
  • steam2pipe
    steam2pipe Member Posts: 59
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    Thanks. The boiler piping does not match the manual only we just found this out 2.5 years after the boiler was installed. The boiler does get skimmed. In another Heating Help discussion I am learning about what a header and equalizer are and there is agreement there by those responding that the piping was done incorrectly. I'm waiting for a quote on what is involved and how much to fix the near boiler piping. Thanks, everyone, for the info on the radiators (1 pipe/2 pipe air vent system). The only time the water hammer subsides is right after skimming and then it is not much longer before it gets loud and clangs again. I think the boiler is producing wet steam and I'm doing my best to get my arms around all of this so that when I do talk to the plumbers we are interviewing to fix this, that I know what they are talking about.