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Residential Steam System - No Traps?

P McNulty
P McNulty Member Posts: 13
I'm just a homeowner... so bear with me...

I have two pipe steam system, 100 yr old house in NE, new furnance, new main piping, new main and radiator vents. System gets good'n hot (too hot on 2nd floor) and bangs like crazy (did this before the new furnace).

Question - each radiator has two valves (supply and return) - both are full open. From what I can tell, none of them have traps on the return. Its been like this since I moved here ~20 years ago.

Could it be there are no traps, and could this be my problem? Any ways to check?

Thanks for listening, and sorry if this is contractor only forum.


PS - Dan's book is on its way here!


  • it sounds like you have

    a two pipe air vent system which didn't use traps..each radiator outlet should drop independantly into a wet return.
  • Steamhead
    Steamhead Member Posts: 16,726
    Right, Gerry

    with valves on the supply and return of each radiator, and an air vent on each radiator, it's two-pipe air-vent.

    Paul, the first thing to do is crank the Pressuretrol down! It sounds like steam might be getting into the return lines and low pressure will minimize this. Your system was designed to run on no more than 2 pounds of pressure, and that was on the coldest day of the year.

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  • Mad Dog
    Mad Dog Member Posts: 2,595
    No sweat Mc Nulty...like those episcopal church signs say......

    all are welcome here. Yep guys are right. Mad Dog

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  • P McNulty
    P McNulty Member Posts: 13

    Thanks for the feedback.

    I checked the pressurtrol. It was at about 1 pound cut-in with differential set at 4. I left cut-in at 1 and reduced diff to about 2.

    Boiler turns off at between 2 and 3 pounds now. Seems to be about 3-5 minutes from cut-in to cut-out.

    Still some banging, but not as bad. House is pretty old and pretty long, its possible some of the supplies have settled and some condensate is caught in there.

    Anyway, Dans' book arrived. I'll look at it, and will also look for(ie hire)some professional advice.

  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    I'd drop that pressure even lower

    1/2 lb cut in 1 1/2 out. Each extra lb of pressure will cause the condensate to back up another 28 inches. I bet most of your remaining banging will be eliminated if you drop the pressure further.

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