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Jackmartin Member Posts: 196
I ran across an interesting condensate return and I wanted to run it by someone else for clarity. This is in an old building, basement suite, down feed from one inch mains. Each tiny rad has it,s own dedicated drop. The condensate line is or was ,someone long ago changed it to 3/4 nominal tube, one inch steel. The system never worked after the copper replacement, I wonder why. Single pipe low pressure steam. The original condensate line installed by the dead men was one inch steel and because of the geometry of the space they put the pipe on beam hooks screwed to the baseboard with little or any slope. I was talking to an elderly gentleman and he tells me before they put in,his words, crappy copper it worked well. I know we are supposed to grade the line but in this case it was clearly impossible. Now, they have hired a contractor to reinstall the rads 3/4 of the way up the wall so they can get slope and on a system with maybe 40 EDR a 1/1/4 condensate line. I calculated the heat loss from 60 feet of bare steel pipe at 215 degrees and it is a little over 13,000 btus. Somewhere, in my reading this is a recipe for water hammer ,I cannot remember if it was in Dan,s books or Jacob Myron ,I am going to do some more reading tonight. All the best Jack


  • Jamie Hall
    Jamie Hall Member Posts: 22,147
    The condensate line doesn't really have to slope, although it's nice if it does have a consistent pitch for cleaning -- but it doesn't have to be much. If any. Nor does it need to be all that big; the flow through it, after all, is pretty small.


    If it is fed by drips, or in this system with downfeed radiation then feeding into the wet return, the pressure in the boiler must be low enough so that water never ever backs up into the radiation, never mind the steam runouts to the radiation. I'm going to go out on a limb here and, sawing madly, bet that the pressure is high enough that condensate is being held up in the radiation. Might not seem too high -- but remember that 1 psi will raise water 28 inches...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 10,905
    How does this return terminate at the boiler?
    Is the boiler on a lower floor?
  • Danny Scully
    Danny Scully Member Posts: 1,413
    edited September 2018
    1-1/4 is oversized for 40 sqft. 1” can handle over 700 sqft. Not so say there is anything wrong with doing it in 1-1/4, but just so you know.
    EBEBRATT-Ed Member Posts: 14,534
    Wet return dosen't have to have pitch but could be getting air locked if no way for the air to get out.

    I am with @Jamie Hall on this one condensate backing up into radiation maybe they raised the pressure?

    Condensate pump may be the fix
  • Jackmartin
    Jackmartin Member Posts: 196
    Thank you to everyone who took time to comment. I am constantly amazed at what I call hysterical knee jerk reactions. I have noticed that customers always listen to the last "expert" on the job if they.say "Well this gauranteed to work". The engineering and expérience factor is forgotten, they know better than anyone because bigger is always better. Why do we bother reading, trying to learn more each job if the idea bigger is better trumps all the arguements you make based on engineering facts? I suppose it wil never change and customers will pay through the nose because bigger has to be better. The only time bigger is always better applies to your bank Account and the health of you and your family. All the best Jack