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Hoffman 75 Main Vent

Jeff_4 Member Posts: 15
I currently have THREE Gorton number 1's working on my longest steam main. It heats without much of a problem and gets hot rather quickly. I do have one radiator on my third floor that heats rather slowly, and I have tried every vent on it to get it HOT. Now, I am using a "C" Gorton vent and it still needs SOMETHING. My plumbing supply store suggested I use a Hoffman 75 to get all that air out of the main. He said it would be better than using the three Gortons that are at the end of my dry return just before it dips down to become the wet return. Shall I spend the $60 or will it produce the same results. Cut-in is 1/2 lb Cut-out is 1.5 lbs. All the other 10 radiators work wonderfully...thanks to Dan's book and all you wet-heads!


  • Drod
    Drod Member Posts: 59

    Last year I went through a similar project/problem-couldn't get enough heat to an upstairs radiator that was at the end of the line (single pipe steam). Unfortunately I spent too much money buying and searching for the "right vent". Finally, I took a step back and looked at the shut off valve (after a thread here got me thinking about it)on that radiator. You probably guessed it-the shut off valve was not the typical "pot bellied" type needed for steam-someone had replaced it. I changed the valve to the correct steam type-and now there's heat from that radiator like we haven't had in years. Good luck.
  • Jeff_4
    Jeff_4 Member Posts: 15
    I wish that was the case...

    with this old girl. I removed the rad...checked for sludge...none....and even checked the shut off valve. Not a single problem. I am still thinking the main needs to be vented more.....
  • Fred Harwood
    Fred Harwood Member Posts: 261
    Slow radiator

    Once I took off the radiator valve and happened to look down the riser only to see an odd piece of steel blocking the riser. I fished it out and all was fine.

    Have you disconnected the rad and fired the system briefly to see for yourself just what's happening in the way of air, steam, and the volume of both leaving the valve? Put a pan under the valve when you do this.

    You could also try flushing the riser with a garden hose, to see if scale or junk is trapped in an elbow somewhere.
  • Jeff_6
    Jeff_6 Member Posts: 1

    I didn't see anything down there. I know you know quite a bit, Fred, as I often see you respond so sharply to others. Do you think I should NOT change to a Hoffman? I suppose I could try the garden hose thing, too!
  • Bob W._2
    Bob W._2 Member Posts: 79
    I don't think a Hoffman 75 vents more than 3 Gorton No. 1's....

    from what the charts say. Vent the riser just before the rad to get the air out of it, since the main is already venting quickly. You could drill and tap the riser just before it goes to the top rad, and use a Gorton No. D, which has the same venting capacity as a Gorton No. 1. Or you could move the rad over and vent the top of the riser, per that master venting method that Dan cites in his book. Then you could use an adjustable vent or TRV on that rad. Hopefully Steamhead will respond to your post and pass judgment on all this advice.
  • J.C.A.
    J.C.A. Member Posts: 349
    How about....

    Slowing the vents near the thermostat and making the heat get to that last radiator ? Just a thought . Chris
  • Jeff_4
    Jeff_4 Member Posts: 15
    The entire house heats very well...

    and my rad near the thermostat vents rather slowly to get the others to heat the rooms they are in correctly. The third floor rad heats..but neglects its last column or so even on the "coldest days."
  • Steamhead
    Steamhead Member Posts: 16,715
    Gorton#1 vs. Hoffman #75

    Both of these vents have about the same capacity. If you replaced three G-1 vents with a H-75, you'd be going backwards!

    We've had a lot of good advice in this thread. What I'd do if we still had problems is to see if the pipe from the steam main to the radiator is longer than usual. If so you need more vent capacity to clear the air out of the pipe- either on the radiator or the riser.

    If the pipe's length wasn't the problem, and there was nothing physically blocking the pipe, I'd check to see if the pipe was sized correctly. A too-small pipe won't pass enough steam to fill the radiator. The same thing can happen if the pipe is pitched wrong, allowing water to accumulate (and usually, but not always, causing banging).

    The main vents should be sized to fill the main with steam in a minute, measured from the time the boiler starts making steam. If one radiator is slow, we need to focus on that one radiator and its associated piping.

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  • Fred Harwood
    Fred Harwood Member Posts: 261
    Slow rad

    Find the EDR of the rad and then check the size of the feeder. (Others also mention this below.) If the feeder length or diameter is too small, you have your answer and a possible solution.

    Missing insulation on the riser will also reduce its capacity to deliver steam to the rad.
This discussion has been closed.