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Do Big Mouth Vents Ever Fail Closed?

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dennis53
dennis53 Member Posts: 68
in Strictly Steam

3 story building, 9 radiators total on 2 mains, one pipe steam. All radiators on the west main failed to heat all at once, rads on the east main are fine. The west main has a relatively new Big Mouth Vent. Do the Big Mouths ever fail in the closed position? Thanks for your experiences.

Dennis

Comments

  • mattmia2
    mattmia2 Member Posts: 15,992

    easy enough to remove them and see if you can blow through them. it isn't the more likely failure mode but it is possible. much more likely condensate trapped somewhere or water being thrown out of the boiler.

  • ARobertson13
    ARobertson13 Member Posts: 128

    If you look at how it is constructed with a bellows as a expansion device, if it is operated in the proper orientation, It is highly unlikely to fail to open. Also, If you do not allow it to cool down sufficiently during the heating cycle, it will not open. There is a video on Youtube ["big mouth Update" 2016] covering its construction.

    dennis53
  • 109A_5
    109A_5 Member Posts: 3,684

    Just look in the exhaust port the valve it easily seen.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • ChrisJ
    ChrisJ Member Posts: 17,148
    https://forum.heatinghelp.com/discussion/comment/1882062#Comment_1882062

    Wouldn't they fail due to loosing the charge in the bellows?

    That would fail open no? I'm picturing the bellows as acting like a spring and retracting without a charge.

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

    109A_5mattmia2
  • mattmia2
    mattmia2 Member Posts: 15,992
    https://forum.heatinghelp.com/discussion/comment/1882069#Comment_1882069

    i think they are filled with an alcohol solution so it may leak as a liquid or gas, it isn't like a refrigeration t-stat where it is charged with refrigerant but it will still fail open if it springs a leak.

    ChrisJ
  • ARobertson13
    ARobertson13 Member Posts: 128

    Yes, Bellows type vents will not close if they are punctured or loose their ability to contain the gas or liquid within them.

  • dennis53
    dennis53 Member Posts: 68

    Just a quick update on the Big Mouth vent that was acting like it was stuck closed.

    It happened on a very cold day when the boiler was running frequently. All radiators heated fine on the first cycle, but the Big Mouth stayed closed between boiler cycles and never opened again because of the retained heat. All that brass in a warm boiler room kept the vent closed.

    In the video referenced above at 2:15, Peter says the disc remained closed after the steam was released and even after the vent was removed from the rack.

    https://www.youtube.com/watch?v=OWoAReeOutg
    Dennis
  • ARobertson13
    ARobertson13 Member Posts: 128

    Yes, I mentioned this in my January 13 post. The heat in your mains pipe will contribute to this. The ambient temperature in the boiler room is not much of a factor. I assume you are using a thermostat to control your boiler. This happens with thermostat controlled systems and some of the heat timer settings in the cold winter months.

  • dennis53
    dennis53 Member Posts: 68
    https://forum.heatinghelp.com/discussion/comment/1882827#Comment_1882827

    What you described is exactly what happened. I ended up moving the vent further away from the main.

    If that doesn't fix the problem, I will add a different style of vent, either a Gorton or a Hoffman 75. Any difference in the opening/closing temperatures between a Gorton #2 and the Hoffman 75?

    Dennis

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