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2-pipe steam system air vents on dry return leaking water

SteveSteve Posts: 534Member
Having trouble getting the water from the return lines back to the boiler. We changed some bad steam traps. Removed (2) F&T traps which were on dry returns (somebody had tried to master trap both sides of the house). Then realized someone had removed the dry return going back to the boiler room. We have vents on the steam mains (no problems working well). We also have vents on the dry returns before they drop in to the wet return (which come from the drips at the end of the steam mains. There are (2) steam mains going to each side of the house). Radiators all appear to be working well now, but a lot of water coming out of the vents at the end of dry returns before they drop in to the wet returns. I realized that someone had removed the dry returns going back to the boiler room. I have a 3lb pressure gauge on the boiler. Once the pressure hits between .5 and 1lb vents on the dry returns will start squirting water. I'm happy to reinstall the dry return back to the boiler room but don't fully understand how if I tie it into the wet returns before the hartford loop it will be any different then tying it in to the wet return 20-30ft away. I just want to make sure that if we do reinstall the dry return, it will solve the problem. I'm also thinking maybe we need condensate or boiler feed pumps. Looking for some advice

Boiler was replaced some time around 2005. I don't know when the dry returns were removed. Wet returns run on the floor back to the boiler room. Boiler is in a pit approximately 12" below the floor where the wet returns run. I can run the dry returns back to the boiler room and tie them in probably 12" lower then they're tied into the wet return right now. Just not sure that will make a difference. I know I have to have good quality main vents at the end of the dry returns. Boiler is also flooding and going off on low water at different times.

Just to recap: These are my possible options:
1. Install (2) boiler feed pumps: (1) at the end of each dry return and pump the water back to the boiler. This should definitely solve the problem.
2. Reinstall the (2) dry returns back to the boiler room and tie in before the hartford loop. Not 100% sure this will solve the problem but it's possible that the wet return pipe size is not large enough to bring all the condensate back from the returns as well as the condensate from the steam mains. That added to the fact that there will be no pressure in the dry return and there will be some pressure in the wet return could equate to the fact that we are not getting water from the dry returns back to the boiler. Instead it's squirting out of the vents on the dry returns. If I do run the dry returns back to the boiler, and it doesn't solve the problem. I may still end up having to install a condensate or a boiler feed pump. Another factor is, I don't know where the old water level on the old boiler was. This was all done before we got there. I will measure the B dimension later today and repost, but educated guess, it's approximately 36" maybe even less. I did also consider installing a vaporstat, but if I have water spitting out of the vents at .5lb I think I will need at least 1lb cut out to operate the system properly. Any advice greatly appreciated.

Comments

  • Jamie HallJamie Hall Posts: 8,227Member
    First thing I'd look at, before I started on the rest of the stuff, is those wet returns. Are they in fact really clear? Or is it possible that they are gunked up? Also check elevations. You probably have ample height, but... worth checking. Keep in mind that the dry returns are, or should be, at or very close to atmospheric pressure, so you need 28 inches per pound to keep them dry.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • SteveSteve Posts: 534Member
    Yes we checked out already water flowing freely through the wet returns
  • SteveSteve Posts: 534Member
    Yes you need 28 inches per pound or 0.434 pounds per foot
  • SteveSteve Posts: 534Member
    B dimension is 43 inches
    I’m going to give the customer option of
    1.two small condensate pumps
    2.Reinstall old dry returns Use a vaporstat and keep the cit out pressure below 1 pound.
    I prefer option two but hdad room in the basement maybe an issue for them.
  • SteveSteve Posts: 534Member
    Cut out pressure
    Head room
    Sorry for the typos
  • JUGHNEJUGHNE Posts: 4,360Member
    Would this originally be a 2 pipe counterflow system that someone thought the dry return was not needed and removed the headache piping?
  • SteveSteve Posts: 534Member
    Yes dry return was removed
    Return main Dripped into wet return
  • JUGHNEJUGHNE Posts: 4,360Member
    Is the dry return dripped down low into the wet returns or tied in above the standing water leg of the main drips.
    Can the end of main steam pressure back up into the dry returns or is there enough water column on the dry return drip to prevent that.
    Can the pressure push the condensate back up into the remaining dry mains that have no pressure?
    What is the size of the wet return, could it be too small?
    Based on EDR of radiation I believe.

    How long have they have this problem?
  • SteveSteve Posts: 534Member
    Originally one was tied in above the waterline we tied it in as low as possible both are now tied in below the waterline
    I have checked With a thermal imaging camera it does not appear steam pressure is pushing up the dry returns rather it is not allowing the dry return to Drain also I suspect return is too small.
    If I run new dry returns I can tie them in at the boiler probably 14 inches lower than they are now I guess that’s my real question will it solve my problem I know I will need to keep the pressure below 1 pound as I do not have a Enough b dimension.
  • SteveSteve Posts: 534Member
    We are replacing the dry returns today wyet return is inch and a quarter.
    I know the parts of the dry return that were cut out was inch and a half,
    Will keep everybody posted any advice still appreciate it thanks
  • SteveSteve Posts: 534Member
    Bump
  • nicholas bonham-carternicholas bonham-carter Posts: 7,164Member
    If you want to see how high the waterline gets in the dry returns, you can get a length of clear plastic hose from the hardware store with a hose adapter fitting. Attach that to the boiler drain valve, and hang the tubing end from the ceiling.
    When you open the drain valve, the water flows into the tube, and rests at the same level as the waterline. When you fire the boiler, and it builds some pressure as the air is being expelled, the water level in the tube rises up to compensate. At peak pressure the difference between the two water levels will be 1.75 inches per ounce of pressure. This is the same level as inside the wet returns up to the dry returns.
    If the water level rises up to the height of the dry returns, then the main vents will be submerged and prevented from doing their job, so keep the pressure low!!
    Don’t forget to close the drain valve at the end, as that tubing will not last long in contact with hot water.—NBC
  • SteveSteve Posts: 534Member
    Dry returns replaced vaporstat installed
    Cut in 3 ounces cut out 14 oz.
    All working good.
    Another lesson learned always try to find how it was originally.
    Never presume the last guy knew what what he was doing.
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