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Steam in my returns and not my mains

I have (apparently) an early version of a two-pipe steam system described in this earlier <a href="http://www.heatinghelp.com/forum-thread/129261/2-pipe-radiator-explanation-new-to-steam">post</a> (<a href="http://www.heatinghelp.com/forum-thread/129261/2-pipe-radiator-explanation-new-to-steam">http://www.heatinghelp.com/forum-thread/129261/2-pipe-radiator-explanation-new-to-steam</a>).   The system is largely unbalanced and only about half the rads heat up.  After replacing and adding main line vents without any change, we're looking for other issues.  One is that a fairly large main that supplies several radiators towards the back of the house has a spot that will stop cold (we added a vent further down, but it didn't help).  By feeling the pipe, I can tell that the steam hits an elbow (pictures below) going upstairs, and then maybe 10 seconds later, the steam comes out of the bottom of that fitting into the return (3/4" copper).  It then follows the return all around and actually starts heating up some of our cold radiators up from the return side.  So my main question is...how can I convince that steam to follow through to the end of the main, instead of diverting into the return.  Like I said, I added a vent nearer the end of that line, but the steam didn't follow.




  • TomM
    TomM Posts: 233

    maybe make a sketch of the setup?
    beautiful Conshohocken PA
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    There is no way

    that that copper return is original.  Nor even that old; that's a kludge someone put on there not all that long ago (well... depends on one's point of view, I suppose.  20 years?  30 years?  That's new... !).  So practically the first question I would ask myself is... where, if anywhere, did the Dead Men intend the pipe (if there was one) in the bottom of that elbow to go?  Did it, perhaps, go into a wet return to the boiler, and serve as a very useful and handy drip for that portion of the line and the section of main going upstairs there?  I wouldn't be too surprised.  But if it is a dry return now... it's a real handy place for steam to go.  Something to puzzle out while poking around in the basement -- and to restore to the original setup, if you can.

    Second, remember that steam goes from high pressure to low pressure -- always.  Therefore the flow resistance in that copper line must be less than the flow resistance in the iron pipe going up.  Question is, why?  Are there any low spots on that line going up which might be trapping water?  That'll do it.  I take it that that line goes upstairs somewhere, then eventually has your new vent on it?  Whatever, for some reason that line has more resistance than the copper, and you will need to find out why and where.

    But do figure out what that copper line replaced, if you can.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Baynton
    Baynton Member Posts: 6
    Sketch of that portion

    Here is a simplified sketch of that portion of the main.
  • Baynton
    Baynton Member Posts: 6
    Good word...

    Kludge is appropriate to many things on the system (not to mention the entire house).  There are several very obvious amendments to the system, and a lot of copper.  There is a radiator under the stairs to the first floor, which I assume they put in when they put in a new (40, 50? year old) staircase.  I assume they messed with that return to accommodate the rad return, maybe turning it from a wet to a dry?  That one staircase rad is the only thing it picks up besides what drips back down the pipe that shoots upstairs.  I wonder if we could turn it wet again....

    This is just a small section of the system (we have 19 rads), so I'm assuming that loosing all that steam to these returns might be somewhat of a culprit in our cold radiators.  I'll investigate more to what that pipe supplies upstairs, you seem to suspect something fouling up the pressure there. 

    Thanks for the tips!
  • Schematics

    Do you have a copy of "The Lost Art of Steam Heating? If not it would really help you to get one as then we could refer you to page numbers of articles and drawings that would help you out. Here's a link to where to get "the Lost Art..." http://www.heatinghelp.com/products/Books/5/68/Lost-Art-Of-Steam-Heating

    I've attached the schematics of a typical one pipe and two pipe system.

    Study particularly the Wet Returns and find where they are located on your system.

    Note that the Dry Return (main) and Wet Return (main) are part the same piping. The deciding factor as to whether it is a dry or a wet return, is whether it is above or below the Boiler Water Line. Your system won't have some of the items that are in the two pipe schematic such as traps. What you need to do is check the return lines from the two pipe radiators as they should lead down and connect to a the wet return. There should also be a dry return leading from the end of the steam main back to the wet return as in the drawings. The returns must be sloped so that condensate (water) will flow back to the boiler. Check your system and see how it compares.

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    A radiator under the stairs?

    People hide them in the darndest places!  I presume there is a steam supply for that one, too?  If it is more devious than this return arrangement, the steam will follow the return.  Those one and a half pipe systems were outrageously sensitive to pressure drops.

    I still have a hunch that this return was meant to be wet, if it was meant to be at all -- how hard would it be to make it do that?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
This discussion has been closed.