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Increasing Main Venting

With hopes of optimizing my main venting - which currently consists of a single Hoffman-75 vent - I have found a 7-inch long section of my main (2 1/2" pipe) which is very close to where my two mains converge prior to heading to the return. I believe this is the best place that I can find to add main vents. Since there is only 7 inches of pipe to work with I believe that I do not have enough space to fit "nipple + union + nipple + tee + nipple". So I plan to use "nipple + union + nipple" and have a pipe-fitter tap one of the nipples with a 1" pipe.

I have been using Brad White's drawing as a bit of a guide (thanks Brad), but won't be able to execute it exactly because of head room.

So a few questions:

1) Is the placement of these vents OK? I don't believe I  have any other option at this time so I am hoping that venting in a not-perfect location is better than almost no venting at all. After all, won't the steam always seek the path of least resistance and move the air out the vets anyway?

2) Brad's drawing shows the need for a minimum of 6" height from the main. Is the fear of being too low have to do with condensate creating a block?

3) Do you all see any other issues with what I am thinking about doing?

4) This is the correct thing to do - right? Hoffman-75 only has 0.75CFM of venting at 2oz while 4 Gorton #2s will get me 7.0CFM.

Sorry for the bad drawings. Hopefully they are somewhat helpful. If it isn't clear, picture #3 is what I propose to place in the orange box shown in picture #2.

As always, thanks for everyone here on The Wall. And I look forward to hearing from you.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,573
    Venting possibilities

    Are there dry returns on your system? If so, I would say that the best place for main vents would be close to where the returns drop down and become wet.

    A bigger layout plan would be more useful for use to see the whole system.--NBC
  • butlermog
    butlermog Member Posts: 50
    More Pictures

    NBC -

    I'm not sure if these will help, but it's worth a try.

    The normal water line of the boiler is about where the black horizontal line is drawn in the second picture.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,573
    Main vent location

    I think a better place might be the vertical part of the dry return before it becomes wet.

    That wet return looks awfully small, and would be better off being lower, especially if you ever change to a different boiler with a lower waterline. Steamhead posted a picture of vents on the vertical return but I can't find it now.--NBC
  • butlermog
    butlermog Member Posts: 50
    RE: Main Vent Location

    Thanks NBC,

    I'm not sure if I would be able to get the dry return unthreaded - which would make a for a potentially long and difficult modification. Perhaps that will have to be tried next summer instead of 3 days before the weather gets cold here.

    I haven't had luck finding the pictures from Steamhead that you are referencing either, so if you find them please let me know. I think I know exactly what you're talking about, but can't say I've ever seen it done.

    If I do look to put vents there I assume they'd need to be as high as possible - right?

    Since I'm thinking that my original plan will be "easy" to accomplish does it sound worthwhile for this year until I'm able to do more work?
  • butlermog
    butlermog Member Posts: 50
    Updates After Adding Vents

    Basic information if I haven't said it yet:

    2-pipe vapor system with orifice valves  (about 3 ounces) with about 645 square feet of used radiation. 406 square feet on main #1, 238 square feet on main #2.

    Weil McClain EGH-85 boiler

    assume all steam traps are failed open (all radiators heat)

    end of dry return has open 3/4" pipe

    More drawing and pictures are attached.

    i have added a Gorton #2 along with 2 Hoffman-75 vents from a 3/4" tapping at the location noted above (at the end of main #1 just before it meets up with main #2). the original Hoffman-75 is still located in the original place at the end of main #2.

    i have also calculated my horizonal mains to be 126ft of 2 1/2" pipe and 38ft of 1 1/2" pipe giving me a total of 4.312 cubic feet of air to move out of the pipes.

    With these newly added vents i am seeing steam at the vents about 4 minutes after steam is at the header. i do not have a good reading on how long it took to get steam at the original Hoffman-75 prior to adding these new vents.

    Cycle time seems to have not change since adding the new vents

    1) Since cycle times seemed to have not changed, is it possible the new vents haven't improved the steam getting to the radiators?2) Any thoughts on why is it taking 4 minutes for steam to reach the vents? In theory the vents attached have the ability to vent 4.0CFM and there is 4.312CF of air. Could wet steam caused by the poor near boiler piping be effecting the steam this much?

    2) Any thoughts on why is it taking 4 minutes for steam to reach the vents? In theory the vents attached have the ability to vent 4.0CFM and there is 4.312CF of air. Could wet steam caused by the poor near boiler piping be effecting the steam this much?

    3) Even with the orifice valves could the failed steam traps be hurting me very much?
This discussion has been closed.