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No vents, boiler replacement, possible vacuum system

WayneMech
WayneMech Member Posts: 53
Just looked at a boiler replacement candidate. Their gas consumption skyrocketed three years ago, and they had a hard time finding a contractor to deal with it. Local contractor thought it was hot water, but begged off when he found it was steam. Large tank above boiler looks like an old style expansion tank, but is a DHW tank (no heat exchanger) with (I believe) an immersed coil feeding it. The building cold water still passes through this, just before entering the upright water heater.
The boiler (Iron Fireman) has the sight glass inside the jacket, with a factory cutout for viewing, and an old red Hoffman water feeder (#4?). I am told it was originally coal fired. The house was built in 1911, by a rich family , in a small Midwest town. It has a really old Burks condensate pump and tank, that may be original. The radiators are all trapped. To their knowledge, nothing has ever been done to the traps. There are no vents, except the open condensate tank vent pipe.
I believe the last of the traps failed, leaving the heating, mostly, to the mains, which are completely uninsulated (this is what heats the basement). The lower water line of the new boiler leaves plenty of height for gravity return, and all the returns are in the basement ceiling. My question is this: Is it possible to eliminate the condensate tank, and just use the gravity return? I know that doing so would require piping in a vent (Hoffman # 75). What if I put a # 76 in? Could I transform this 106 year old, pumped return system, into a gravity return, vacuum system?
Please give me some guidance, guys.
Thanks,
-Dale

Comments

  • Steamhead
    Steamhead Member Posts: 16,726
    The short answer is, maybe. Where is this job located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,329
    you need enough stacking height for the condensate to get back to the boiler with 1-2 psi in the boiler. Figure it out with a tape measure
  • MilanD
    MilanD Member Posts: 1,160
    edited May 2017
    If the system is tight, maybe able to go to vacuum. You do need extra hight for dimension A at the drip (M on the attached pic), 24" for each inch of vacuum.
  • WayneMech
    WayneMech Member Posts: 53
    It is located near Peoria, IL. I have 40" between the steam main and the water line.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    There is certainly a need for height to accommodate pressure pushing up the water in the wet returns, (1.75 in/ounce of pressure), but I'm not sure I see the need for 24 inches of height per inch of vacuum.--NBC
  • MilanD
    MilanD Member Posts: 1,160
    > @nicholas bonham-carter said:
    > There is certainly a need for height to accommodate pressure pushing up the water in the wet returns, (1.75 in/ounce of pressure), but I'm not sure I see the need for 24 inches of height per inch of vacuum.--NBC

    Maybe BC vacuum differential will be greater at the return side vs. in atmospheric pressure only setup, thus raising the water higher at the return side. Something like a Romaurie effect in an aquarium. Maybe?
  • clammy
    clammy Member Posts: 3,094
    First and foremost to get the skyrockets gas bills down would be to get the mains and runout insulated and insulated with a mimiun 1 inch wall thickness high denisty fiberglass insulation .You are most likely losing the bulk of heat to the basement .Then see how your system performs .I think i would pook about and see what rements of possible cross over traps in the mains and ends of the mains for possible removed air vents locations .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating