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Should I move the main vent?

ceikey Member Posts: 60
Just wondering if it makes sense to move my main vent from the end of the dry return back to the end of the main??? I have an all one-pipe system now and it seems there would be 2 benefits....

1) Faster for steam to get to it, for it to close and for steam to start moving towards the rads.

2) Also I am about to insulate the mains and it seems I should insulate the dry return all the way to the vent so steam moves to it as quickly as possible. If the vent was at the end of the main, I wouldn't need to insulate the dry return, right?

Thanks for the help.



  • Jamie Hall
    Jamie Hall Member Posts: 22,877
    The real question...

    is how are the mains vented now?  Or are they?  A number of vapour systems use crossover traps from the ends of the mains into the ends of the adjacent dry returns, and then had one (which can be replaced with more than one, at your pleasure!) main vent near the boiler.  There were reasons for that in the old days...  But if the crossover traps are working as they should, they will do a quite adequate job of venting the mains.

    If they aren't working, or someone has removed them if they were once there, or if they weren't there in the beginning, then yes, I would say vents at the ends of the mains would help -- the air has to go somewhere!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ceikey
    ceikey Member Posts: 60
    Not a main vent???

    Maybe I shouldn't be calling it a main vent. I only have the one vent at the end of the dry return. I have a Gorton #2 on there now. There are no vents or traps at the end of the main. It's not a vapor system....or at least I don't think it is but I don't really know the difference either. I thought a one pipe system was one pipe system and a vapor system was completely different. So it sounds like I should move the vent to the end of the main and maybe add a second. The main is about 30 ft long. The first ~5 ft after the header is 2", then a foot or two of 1 1/2", then the rest is 1 1/4". Are there some charts to determine if the one Gorton #2 is enough venting?

  • jpf321
    jpf321 Member Posts: 1,568
    there are charts ...

    buy the Balancing Steam booklet by Mr. Gill available in the Shop here .. it's a "download" but you probably won't be given access until tomorrow business hours .. and the money goes to charity. 
    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm
    my NEW system pics | my OLD system pics
  • ceikey
    ceikey Member Posts: 60
    I see you have a chart

    in your signature jp. I'm gonna play with that a bit to see if it will work for me. I'm limited for height at the end of the mains to put vents in. Is there any minimum nipple length that the vent should be on? By the way, very impressive install...i've been watching your posts.

  • where to put main vents

    keep the vents where they are, at the end of the returns, and make them as capacious as you can. i always think that vents at the end of the mains, might leave a large amount of air in the dry return, which could be a "pressure wild card" as everything heats up, and might contribute to short-cycling-especially if your main venting is not generous.

    you could try both locations for a while and let us know the results.........--nbc
  • ceikey
    ceikey Member Posts: 60
    That makes sense

    Thanks nbc. So am I correct in insulating all the way to the vent then so the steam moves there as easily as possible?

This discussion has been closed.