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AIR VENT

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WP1912
WP1912 Member Posts: 13
edited January 2021 in Strictly Steam
CAN YOU OVER VENT A TWO PIPE THERMOSTATIC STEAM TRAP, "HOFFMAN #8 SYSTEM" ? ALSO I PUT AIR VENTS ABOUT 12 INCHES PAST THE LONG MAIN LOOP ON THE RETURN LINE AFTER THE STEAM TRAP IS THAT GOING TO WORK PROPERLY ?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Well, that's a bit vague. If this is a Hoffman Equipped vapour system, with crossover traps (or intended to have them) the answer is that you certainly can. Those are meant to have one, and only one, vent location -- at the boiler, after the dry returns before they drop to the boiler (or the Hoffman Differential Loop, if there still is one there. The mains are vented through the crossover traps into the dry returns.

    On the other hand, if this is a standard two pipe steam system which happens to use #8 radiator traps instead of something else, then vents on the steam mains won't hurt. If there are crossover traps, they won't help, either. In any event, you still must have vents on the dry returns as above, though -- lack of them will hurt.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WP1912
    WP1912 Member Posts: 13
    edited January 2021
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    The vents are on the returns 12 in past the steam trap in the main to dry loop . No vacuum pump just basic system
  • WP1912
    WP1912 Member Posts: 13
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    Hoping to get the air out of the system quicker and put them on the return after the trap in the loop .  
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Trying to get this clear. You have a steam trap going from the steam main to the dry return. What kind of trap? Hoffman #8 set higher than the main? F&T below the main and the dry return below that? Any drips? Any wet returns?

    It makes a huge difference.

    In any event, on a two pipe system you must -- no options -- have adequate venting on the dry returns, preferably near or at the boiler. These vents vent all the radiators, and in many systems all the mains as well.

    If there are crossover traps -- those Hoffman #*s higher than the mains and going to the dry returns -- you don't need main vents at all. If, on the other hand, you have F&T traps, you do need vents on the mains.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WP1912
    WP1912 Member Posts: 13
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    piped for wet returns only hoff #8,and i repiped it to drop down into the steam trap and then lower to the return . no f and t traps and only maybe a 50 ft run .
  • WP1912
    WP1912 Member Posts: 13
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    ok so what i did was put a radiator steam trap on the end of the loop then put a vent 12 inches on the wet return when all i had to do was put a cross over trap there
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Do you still have dry returns? At this point I admit to being confused...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WP1912
    WP1912 Member Posts: 13
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    i'm sorry only wet returns , my apologize
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    edited January 2021
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    If you only have wet returns, then both the mains and the radiators must be vented, and it is not a two pipe steam system. It's one pipe.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WP1912
    WP1912 Member Posts: 13
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    i figured it out i believe but it is a two pipe system supply and return
  • WP1912
    WP1912 Member Posts: 13
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    thanks Jamie for trying to help i guess my terminology is off still learning
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,529
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    @WP1912

    Pictures are a big help in sorting this out. No one has x ray vision. There are a lo t of different 2 pipe steam systems. One pipe is easier to figure out

    And then you run into one once and a while that has one pipe and two pipe mixed
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
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    Pictures would, indeed, be most helpful. But a quick primer on terminology:

    Steam mains carry, as the name implies, steam, and feed the radiators.

    Dry returns, technically, if you have them, are separated from the steam mains by steam traps, and carry only condensate and air from the radiators. They are usually separated from the radiators by steam traps on the outlet of the radiator -- but not always. They are well above the boiler water level -- often at almost the same elevation as the steam mains associated with them.

    Wet returns are located below the water level of the boiler, and carry only condensate -- they are full of water at all times, and can't carry any air or steam.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WP1912
    WP1912 Member Posts: 13
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    I’m repiping around the boiler . The original from 1900 was probably piped for coal but now has two about 16 yr old Weil McLain natural gas units .should get most the supply’s coming in tomorrow so pics will be coming soon