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Jim Walls_2
Jim Walls_2 Member Posts: 71
Steamhead,& Noel I want to thank you again for the advice, have a couple more questions, by the way I will post some pictures as soon as I can ,,,,,,,,,,,this is a 3 story bldg,,,,,,,above the clg in the basement I did locate a trap on the end of the main steam line & a vent just beyond that on the return just after the trap discharge, vent is not original, appears to be a Hoffman # 74, I will replace this vent. Question is , if this vent is replaced with the correct one, do you think I would need another vent in the boiler room just before the dry return becomes wet, we are talking 40-50'horizontal and elevation change of 10-12'. Also, there were two radiators on the 3rd floor (storage area) which have been disconnected, furthest run in the system, would it be beneficial, (all they did was disconnect pipe & plug), to place vents on the supply to help get the steam to the rest of the radiators quickly?


  • Unknown
    Mo air

    I'd like to relate an experience I had with an air vent at the wrong place on a vapor system. It had a float trap out at the end of the main, which had a return running high beside it, downhill to the trap. The whole return dropped wet there, to go under the stairs. The other side of the house dropped to wet on the other side of the stairs, with it's own main, trap, and high, dry return.

    Someone put a condensate tank in the boiler room, and cut into the high return there, at the HIGH point. The tank vent was an open 2" pipe.

    Now the air all ran UPHILL to the tank vent, and it pushed the condensate of start-up up away from the trap that could drain it away. Radiators were venting but not draining the condensate. It hammered like crazy at startup EVERY time.

    It happened when it came out of setback. Early every morning.

    I had an old Trane vent that I put on the high return at the DOWNHILL end, on top of the float trap. Then I cut out the condensate tank and put in a hartford loop and a feed valve.

    Vent it at the down hill end of the high return past where the main vents into the high return. A vent at the high end blows condensate up the high return, the wrong way.

  • Jim Walls_2
    Jim Walls_2 Member Posts: 71
    Thanks Noel

  • Steamhead
    Steamhead Member Posts: 16,901
    The trap at the end of the steam main

    is probably one that will vent some air. However, it may not vent quickly enough.

    That Hoffman #74 is a high-pressure vent with a very small opening. At the extremely low pressures your Mouat was designed for, it is almost useless. You need a vent with high capacity at very low pressure. The Gorton #2 is such a vent- it was designed for use with Vapor systems. I forget how much radiation your Mouat has, but one #2 should be able to handle 600 square feet of radiation or so when used on the dry return.

    For venting the steam mains, measure the length and diameter of each main and post the figures here. We can tell you what you need, but I'll bet you'll be using Gorton #2 vents on the steam mains too.

    BTW- I've seen the Vapor system Noel was describing- a Milvaco, if I remember correctly. It ran very well after he got it straightened out.


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