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Water shooting out of main vent

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Harvey_2
Harvey_2 Member Posts: 27
in Strictly Steam
I have a system with a problem I have not seen before. When the boiler starts we get water shooting out the main vent. This is a two pipe steam system. We had corrected the near boiler piping a few years ago. I think some of the rad steam traps were/are bad but owner did not want to replace. This started two weeks ago. Any ideas?

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  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
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    fix the bad traps

    not to be glib, but that's where to start.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Dave in QCA
    Dave in QCA Member Posts: 1,785
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    Please Clarify

    You say water shoots out of the main vent when the boiler starts. 

    Does this happen before the radiators are hot?

    Is the vent where the water is shooting out on the end of steam main or on the return piping?

    Is the steam main vented with a vent or a crossover trap?

    How old is the boiler?  New install?
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Harvey_2
    Harvey_2 Member Posts: 27
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    To clarify

    It's worse when coming off nite setback. It happens on normal cycles.

    Comes out the end of the main and it's a vent.

    Boiler is about 7 yrs old
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
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    what is the pressure set at

    and is the return pumped or gravity?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Dave in QCA
    Dave in QCA Member Posts: 1,785
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    a guess

    I am going to assume several things about the system that I don't really know.  They are that the piping parallel and that any condensate in the steam main is flowing to the end of the main where the vent is located and that at that point there is a drop to a wet return line that might be next to the boiler or a long way from the boiler.  If that return line is open and flowing freely, any water in the main will drop and flow into the boiler because except for minor line losses, the pressure is about equal.  If the boiler is running at 2 psi, the line losses would amount to no more than a 24" difference in head pressure and would NOT cause water to back up into the main.



    However, if the return piping is slugged full of sludge, which can and does often happen, the condensate in the main cannot drain fast enough and will back up into the main.  If it backs up enough, it will start to spray out of the vent.  There is no way for me to know for sure, but based on my limited information of your system, it is a reasonable guess. 

    Let us all know how this turns out.  ~Dave
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
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