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Do Big Mouth Vents Ever Fail Closed?

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dennis53
dennis53 Member Posts: 65
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: 15,831

    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: 123

    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.

  • 109A_5
    109A_5 Member Posts: 3,590

    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: 17,104
    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: 15,831
    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: 123

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

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