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top floor rads not getting hot

zepfan Member Posts: 397
i looked at a job yesterday and to my knowledge it is  one of the only two steam systems in our area.it is a two pipe system with one main hoffmann #75 vent installed on what i think is the f&t trap in the boiler room.the owner had said that the three radiators on the top floor have never gotten hot since he has owner the house.when i got there the boiler had been off at the thermostat for several hours.the burner fired up and the first thing i noticed it took about twenty minutes for the steam header directly over the boiler to get hot,this was on a day when it was 50 outside.while this was happening the hoffmann vent had a very faint amount of air coming out of it.the rads on the first floor got very hot,however these three rads located about ten feet above the first floor were ice cold.i disconnected the inlet to one of the traps on the radiators,got a little air out of it,but then nothing.no air,condensate,or steam.at this point the first floor where the room thermostat is got very warm,the room temperature had risen 5 degrees in twenty minutes, and shut the burner off.the pressure on the boiler had barely gotten to a half pound,and the hoffmann vent still had very little air coming out of it.i can tap on the side and here the the float inside move,so i am fairly certain it is not plugged. could it be the the air is not leaving the system fast enough for the staem to get past the first floor?i know this is a long story but i am looking for suggestions to what could be causing this,before i take it any further.the steam main if it helps comes off the top of the boiler and runs about 26' and the has all the branchs coming off of it into the walls and floors.none of it is insulated which we know is not helping.any suggestions would be much appreciated.thank you, and i will try and post some pictures


  • crash2009
    crash2009 Member Posts: 1,484
    Posting Pictures

    When you are posting, see that box that says "File Attachment"  Click on the browse button and go to the place you keep your pictures.  You can add more pictures by clicking on the Add Another File button. 

    Try and get some pictures of the radiators, and the boiler room, especially any oddball shaped cast iron pieces down there.  The guys here work with that old stuff everyday.  They will be able to tell you in a half second, whats wrong and how to fix it.
  • Enreynolds
    Enreynolds Member Posts: 119
    What I think you have

    there is not a F&T trap but a vent trap.  They are often found together with a Boiler Return Trap.  We have a Warren Webster setup of this type in one of our apartment buildings in Rochester NY.  We had similar problems with apartments that were not getting adequate heat.  What was happening was that about 30 cf of main air (and all the air in the supplies and radiators)  had to get out through 4 WW 712 crossover traps at the ends of the mains and vent through that one #75.  I suppose that this was fine with the original 1928 coal burner, but we never got the air vented before the thermostat cut off the burner.  I am still working on the system, but currently I have removed the crossover traps and replaced them with 16 Gorton #2s, and removed the #75 entirely from the vent trap.  The boiler return trap and vent trap no longer come into play with the current system, since the water line appears to be much lower than the original, so I don't need to worry about condensate rising that high any more.  Having done this, the heat is MUCH more even in the building, and we have reduced fuel costs by about 2/3 s.  So, the long winded moral of my story is that you need more, better, venting.
  • zepfan
    zepfan Member Posts: 397
    pics of installation

    thanks so much for the help.here are the pictures of the two components in the boiler room.the first i think as you suggested,is the vent trap,and to the right of that is the return trap.please correct me if i have this wrong.the second picture is of the end of the steam main where it goes up through the walls.if i was to add more and better venting where would be the best place to install them?also can you have too many vents in a two pipe system?thank you
  • Steamhead
    Steamhead Member Posts: 16,835
    Definitely a vent trap in the first pic

    and that #75 is way too small to be the only vent in the system. You need at least one Gorton #2 vent there.

    In the second pic I see several pipes that look like they go to radiators, and the last riser that's the same size as the main. Where does this one go?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • zepfan
    zepfan Member Posts: 397
    where to add the gorton #2

    thanks for the help.i think the end of the main that goes up through the floor goes to the second floor radiators that are the ones not getting hot,but i intend to go back to confirm this.should the hoffman vent be kept in place on top of the vent trap and the the gorton vent be installed in another place? or should the hoffman be replaced by the gorton,on top of the vent trap?thanks again
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