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Main Vent Sizing and Placement

Kev3bKev3b Member Posts: 18
Hi all.  Looking for some information on how to properly calculate what main vent would be best for my system. 

I have a one-pipe steam system powered by a Burnham low-pressure boiler.  Last year I replaced all the radiator vents with Ventrite #1 adjustable vents and the main vent with a Gorton #1.  The system is running much better than when we first moved in, but I wasn't sure if I needed more venting.

The boiler sits roughly in the middle of the basement and the main runs down the center of the house, one section towards the front and one section towards the rear.  From there, smaller diameter pipes extend off the main and run parallel towards the sidewalls of the house before bending vertical towards the radiators.  My question is now, when calculating for the main, should those parallel sections of pipe be included?  Also, do you include the vertical length of the pipe to the radiator or is that the responsibility of the radiator vents to vent that portion of pipe?

Also, my main vent sits at the end of the wet return on the elbow before it returns to the boiler.  Should I consider raising it off this elbow? 

Header - 3 ft. of 2 in. pipe

Riser - 2 ft. of 2 in. pipe

Main - 29 ft. of 1 1/2 in. pipe

          - 18 ft. of 2 in. pipe

Return - 18 ft. of 1 in. pipe

Horizontal Extensions off Main Pipe In Basement

Total of 6 ft. of 1 1/4 in. pipe

Total of 62 ft. of 1 in. pipe

Attached are some pictures of the set-up and a diagram of my piping system with pipe sizes and lengths.

Thanks in advance



  • BobCBobC Member Posts: 4,456

    The main vent has to vent the air in the boiler, boiler header, and the steam main. Each radiator vent has to handle the air in the radiator and the piping from where it comes off the steam main.

    You could probably use a second Gorton #1 beside the one you have. The boiler header looks a bit low but if everything is heating up at about the same time your probably ok.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    edited November 2013

    Don't forget to insulate the header and supplies-even with fiberglass batts if no real pipe insulation is available.

    As you can never have too much main venting, adding a Gorton 2 on the main would be good for steam speed of arrival. A 0-3 psi gauge will tell you when there is enough venting to equal the open hole capacity.--NBC
  • Kev3bKev3b Member Posts: 18
    Thanks Bob

    Thanks for the response Bob.  Right now, all the rads get heat at relatively the same time, so even distribution hasn't really been a problem.

    I like the idea of adding another Gorton #1 than buying a Gorton #2, since I just purchased the Gorton #1 last year. 

    In regards to the main vent's current location.  Do you think it would be wise to move it up and off the elbow at the end of the return? 
  • Kev3bKev3b Member Posts: 18
    Thanks NBC

    Thanks NBC.  I will look into adding insulation before it starts getting really cold.
  • BobCBobC Member Posts: 4,456
    edited November 2013
    Up and away

    I would put a short nipple where the vent is and then an elbow and a 12" nipple. Run that nipple back along the pipe so it will drain towards the return then add a T, a short nipple, another T, and a plug -  then put a Gorton #1 on top of each T. use whatever size nipple you can to get the vents up away from any water slugs. You can use different size nipples to avoid floor joists.

    The Gorton #2's are great vents but they don't give them away, might as well use what you have.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Kev3bKev3b Member Posts: 18
    Pipe Calculations

    So I decided it would be well worth my time to purchase the Balancing Steam Systems, Using a Vent Capacity Chart pdf.  From the charts in the pdf I came up with the following calculations.


    23 ft. of 2 in. pipe - 23' x .014 = .406 cu.ft.

    29' ft. of 1 1/2 in. pipe - 29' x .023 = .529 cu.ft.

    Return - 18 ft. of 1 in. pipe - 18' x .005 = .09 cu.ft.

    Total - 1.025 cu.ft.

    Gorton #1 = .330 cu.ft. per min. @ 1 oz. per

                       = .540 cu.ft. per min. @ 2 oz. per

    Based on these calculations I would need either 2 or 3 Gorton #1's.  I'm not sure whether to use the 1 oz. or 2 oz. calculations.  Does anyone have more experience with this?
  • SteamheadSteamhead Member Posts: 11,382
    I'd use the 1-ounce figures

    that will help the steam favor the main vents over the radiator vents.

    This puts you in Gorton #2 territory. Might be best to get the #2 and pass your #1 along to someone else who can use it.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Kev3bKev3b Member Posts: 18
    edited November 2013
    Thanks Steamhead

    My only concern is having enough room for the massive #2.  There isn't too much room between the main and the return.  I'll go to my local supply house tomorrow and price out what I need. 

    The price of the Gorton #1 was pretty reasonable, if I remember correctly. 

    Also, a big thank you to everyone else who responded to this post.
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