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Do I need a main vent that opens soon after pressuretrol cuts off burner?

I have a 1-pipe system. And with the help of this board I, was able to replace the two old main vents with 3 Gorton #2s. Thank you! Those Gortons balanced the heat in the house probably for the first time since the house was built. :)

(and yes, I've already heard from this board, looks like my local supply house sold me galvanized fittings even though I asked for cast-iron, and yes, looks like I should have angled the pipes differently to avoid debris from jamming the Gortons. I got that.).

But my issue is that when the pressurtrol shuts off the burner, there is a negative pressure in the mains, and then the radiator vents open and let air in (maybe after 30 to 60 seconds after the burner stops) even though the Gortons are still shut since they don't seem to open up until they are stone cold. So after air has filled the mains via the radiators, the burner will kick back in, and the steam builds up, but the Gortons are still shut, and the only openings to let air out of the system are the anemic little holes on the radiator vents.

So I was thinking maybe I should add another main vent to the contraption pictured below, so there would be 3 vents at this particular location (2 gortons, plus another) -- maybe the third one would be a different make/model that would open up quicker than the Gorrtons so that it would available to expel air after the burner kicks back in?

Or maybe there is another way to solve the problem? Or maybe I don't have a problem?

Any thoughts would be appreciated.



  • Gorton vents slow to react?

    Maybe if you could extend the antler/Menorah/manifold out farther, the vents would cool down more quickly.--NBC
  • MDNLansing
    MDNLansing Member Posts: 297

    Do you have a vapor vacuum system? It sounds like your system is going into vacuum shortly after the boiler stops firing. This sounds a lot like the function of a vacuum steam installation. Do you see any evidence of a second pipe that connected to the radiators? Something small like 1/4 or 1/2 inch pipe that connected where the vents are now. Do you have a condensate take anywhere in the basement? They were usually small and mounted above the water line, collecting condensate on its way back to the boiler.

    If not, you could try raising the cut out pressure just a little to allow more steam to build and satisfy the thermostat before the low limit is reached. This would allow a little more time between the high and low limits. What pressure is the pressuretrol set to now?
  • ChrisJ
    ChrisJ Member Posts: 15,442
    edited November 2013

    I have four Gorton 1s on one main and one on the other (much shorter main).

    After a good long cycle I also hear my radiator vents (also all Gorton) whistling as a vacuum is created and the vents suck air in.  Not a loud whistle, but if your a few feet from a radiator you can just hear it.  Mine is a single pipe system with nothing fancy other than it heats my house cheaply and evenly.

    Doesn't seem to bother anything on my system and the main vents are wide open long before the next cycle begins.

    EDIT : I just read a little more of what the problem is.  Your pressuretrol should let the burner relight before the steam pressure drops that far.  The pressure should never drop below 0.5PSI or so before relighting and if that isn't soon enough move it a little higher.  There is no point in sucking more air in that needs to be pushed back out during a cycle.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Do I need a main vent that opens soon after pressuretrol cuts off burner?

    Hello MDN,

    Nope, not a vapor system a simple one-pipe. Behind the vertical wood stud in the pic you can see a vertical 1" pipe, that's the start of the condensate line at the end of the main,. From there, the condensate goes back down by gravity to a run which ends back at the the hartford loop.
  • Mark N
    Mark N Member Posts: 1,115
    edited December 2013
    Cycling on pressure

    Why are you cycling on pressure? Does the boiler cycle on pressure every time it runs or only when recovering from a setback? Are you actually cycling on pressure or do you have a cyclegard LWCO? This will cut off the boiler to check the water level.
  • Pressuretrol the problem?

    Thanks Chris,

    I think you may have figured it out. As with your system, when the temp hits the mark on the thermostat, then the system goes off for long enough for the steam to all go away and the Gorton #2s are all open before the next cycle starts. That works like it should.

    Problem is the pressuretrol. I know I have a problem with it anyway, it is very hard to adjust with any precision, and I'm pretty sure it's not working right. I plan to replace it soon. Hopefully that will allow me to set it so that, as you say, it kicks the burner back in before the air starts being sucked back into the radiator vents.

    But I would think that if it works as you say, then when the pressuretrol stops things, the burner would come back on in less than a minute. That seems like a very shot time -- is that the way it's supposed to happen?
  • cycling

    (I have a LWCO and that is not the issue here, the water level is usually kept just fine.)

    In normal operation, maximum the pressure is never reached, because the thermostat controls things quite well (I usually leave the thermostat the same day and night). So, in normal operation, the burner kicks in until the house reaches the right temp, and then the thermostat turns off the burner. And during those cycles, the pressures usually never go above 1/2 pound before the thermostat shuts things down. And then the system cools for 15 or 20 minutes, or longer depending out outside temps, before the thermostat calls for heat again. That part works as it should.

    It is when I've been away for a few days and had set the thermostat to 50 degrees. So, when I come home and set to 70, the pressure gets higher and will ultimately be controlled by the pressuretrol. That's this issue I am talking about.

    Another author said that, if I set the pressuretol right, then the burner ought to come back on before the external air is sucked in through the radiator vents. For my system, that means the burner ought to come back on about 30 to 60 seconds after the burner stops. Does that sound right -- that is, to have the burner going off for only a minute to let the pressure reduce, and then come right back on again?
  • ChrisJ
    ChrisJ Member Posts: 15,442

    Can you take a picture of your pressuretrol and its settings?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Rod
    Rod Posts: 2,067
    Main Vent Operation

    Hi- Here's a couple of links which might be of interest to you.



    According to Gerry Gill, the Gorton #2 starts closing at a relatively low temperature.

    I've often thought that it might be an idea to include a Hoffman 75 with a string of Gortons

    I don't know what temperature a Hoffman 75 closes at but it is higher than the Gortons and may be close to that radiator steam trap which is around 180 deg.

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 22,901
    A couple of suggestions...

    first, the system should not go into vacuum during a call for heat from the thermostat (for a one pipe steam system, that is, like yours).  So the first thing to do is to replace that pressuretrol with a vapourstat, and set it so that it shuts off at say 12 ounces or so; that should be plenty.  Then set the differential so 6 or so -- that will start the burner again, if necessary, before the pressure drops to a vacuum (note that if you have a post purge/pre purge in there, it is likely that those will control the burner off time, rather than the vapourstat settings).

    Then you can also add a Hoffman 76 to that menorah (keep the two Gortons).  The Hoffman will open rather rapidly on cooling, and should really eliminate the problem.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Do I need a main vent that opens soon after pressuretrol cuts off burner?

    Thanks everyone, this is all great info. The prior posting confimrs that the Gorton #2s open very slowly, and in my system they should be supplemented.

    I am planning also on replacing the pressurtrol with a vaporstat anyway. I have another post, and have asked there if I should put in a 0-16 oz or a 0-4 pound. Any suggestions, on that? Please post any suggestions at http://www.heatinghelp.com/forum-thread/148155/Replacing-a-Pressuretrol-with-Vaporstat
  • Hoffman 62? Hoffman 75? Hoffman 76?

    OK, thanks everyone. I am going to supplement the two Gorton #2s that you see in my photo with an additional vent. The idea will be that this extra vent should open sooner than the slow-opening Gortons. The various posts have suggested Hoffman 62, 75 and 76.

    So if anyone can suggest why one is right for my situation, that would be great. This is the list of Hoffmans from Pex . . . http://www.pexsupply.com/Hoffman-Air-Valves-301000

    The 62 is shown as a "vacuum breaker" -- I'm not sure what that does -- does that mean it does not expel air when the steam is on its way but that it will let air back in the system when a vauum is present? Or does the vacuum breaker also serve as a regular vent, i.e. expelling air until it gets hot?

    As for the 75, it seems to be a regular air vent -- which might be right for this application(?). There is also a 75H, which I cannot tell what is different (chrome vs copper? or something else?)

    The 76 appears to be a vaccum valve. So same question for that as I had for the 62 -- but the 76 is a full $50 more than the 62!?! So if the 75 (75H?) is not preferred, then is it worth it to spend $50 extra for the 76 instead of 62?

    No one mentioned the Hoffman 4 (cheapest at $49!), but maybe that would be right in this application?

    Thanks for helping me figure out the best valve.
  • Larry_52
    Larry_52 Member Posts: 182
    Hoffman 75

    The Hoffman 75 is the vent for your application. The 75 H is for higher pressure steam. The 76 is for vacuum systems & 62 is for vacuum breaking. I personally prefer the Hoffman 75 to the Gorton 2.
  • bradslees
    bradslees Member Posts: 34
    on a related note...

    does anyone know if the gorton #1 behaves the same as the #2 in terms of opening and closing temps? I'm about to add a #2 to a main that already has a #1 and wonder if I will have this same problem.
  • bradslees
    bradslees Member Posts: 34
    i answered my own question

    I installed the #2 and kept the #1, like I said and sure enough when the system shut down the #1 started whistling so loud I could hear it upstairs. I swapped the #1 with a Ventrite #35 that I had sitting around and the whistling stopped. I have 3 thoughts about what might have happened, curious if you have opinions about which is likely correct.

    1) the ventrite35 doesn't open and the vacuum is eventually just being released through the gorton #2 when it opens (which I don't hear)

    2) the ventrite35 doesn't open and the vacuum is being released through the radiator vents

    3) the ventrite35 is just somehow quieter than the gorton