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Air Valves on 2 Pipe System ?

I have a unique situation, a very old 2 pipe system that in addition to the steam traps

on the radiators, someone installed air valves ( Hoffman #40's) midway up

each radiator on same end as traps.  Isn't this minimizing the operation of the traps ?

To make matters more frustrating, I haven't been able to find a F&T trap anywhere

in the system ( the basement is completely finished ), and finally,  it is venting live

steam out of the end of main air vent.  There is a bit of water hammer at this vent

location at start up but seems to quiet down after it runs awhile. 


  • Dave in QCA
    Dave in QCA Member Posts: 1,776
    edited December 2011
    Sounds like Band-aid repairs

    You situation sounds a lot like what I encountered with the property that I bought a few years ago.  My radiator steam inlet connection is at the bottom of the radiators, so when a radiator would not heat because of a failed trap, a vent allowed it to heat, but didin't fix the broken part.  Also, I had several radiators with traps that had failed open and allowed steam down the condensate line.  The open vent in the condensate return pump was protected by master F&T traps that had been installed in the return lines, but were not necessary and causing problems in the system.  

    1   Repair your radiator traps.

    2   Remove the air vents from the radiators.

    3   Your system may not have any need for F& T traps if the steam mains are configured so that they drain their condensate back to the boiler.

    4   Low pressure is a secret to helping the system work with greatest efficiency and prevents many problems. 

    Here is the link to the thread on my system... I apologize for its length, but it tells the ongoing saga of repair and fine tuning of a good vapor system.   http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • Enreynolds
    Enreynolds Member Posts: 119
    Please Elaborate

    When you state you are venting live steam out of the main air vent, do you mean a vent in the boiler room, or a vent at the end of the steam main?  These are very different concerns.  Pictures are the best way to show what is going on.  Please post pictures of  the "main air vent", piping around the boiler, any "odd" looking cast iron gadgets hanging around, and a representative radiator from both ends and the front.  This will give the experts here a little more to go on.  The one pipe vents added to a two pipe radiator with a steam trap indicates someone without a good understanding of steam was trying to solve a problem with radiators not heating up.  Given what you have said, that was probably due to failed steam traps allowing steam into the returns, and subsequently closing down good steam traps from the return side.  But This is just a guess, until we get more info/pictures.
This discussion has been closed.