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Need advice on my first ADSCO vapor system.... Boilerpro

Boilerpro_5 Member Posts: 407
I reviewed my first American District Steam Company system yesterday that has several obvious problems. It looks alot like my beloved Moline systems, but I wanted to get a second opinion about changes to the system. Here's what I found.

1)New Hydrotherm (Smith) VGA-250 atmospheric gas boiler, rated at 250,000 input, connected to about 40 feet of 3/4 inch gas main, firing about 175,000 input. No header, but Hartford loop piped in off of balance pipe connected to steam main
2)Pressure operating at 2 to 3 psi
3)Several leaks in piping and at original valves.
4)One radiator with standard steam valve, two with gate valves, no traps on any radiator returns.
5)The end of the two steam mains are tied together into a single drip and there is a 1 inch pipe connecting the end of the steam mains to the beginning of the steam mains. This piping all looks original. I suspect the 1 inch line was used to increase pressure at the end of the main so the condensate would not back up into the main since the original boiler water line was probably very high... probably only a foot or two under the mains. One main is multiple times longer and larger than the other.
6) One Hoffman #75 on the end of the joined two return mains. One main is multiple times longer and larger than the other.
7) At the end of the return mains, off the top of the piping there is a 1 1/4 inch line running towards the chimney and capped off.
8) Installed radiation equals 495 EDR or 119,000 btu/hr output. The 2 radiators installed with Gate valves were added off a single riser, but usually are off anyway. One radiator appears to have been removed in the kitchen. At the 80% radiator filled level used for orifice vapor systems, the adjusted radiation is 396 EDR or 95,000 btu/hr.
9) The horizontal return where the end of main drip and the end of return drip drop is above the water line (it looks like it used to be below the water line).

Here's what I am thinking to do, in order of importance.

1)Drop the line in 9 below the water line so steam cannot travel from the supply main to the return main.
2) Eliminate the Hoffman main vent and reconnect the return line back into the chimney to use the chimney draft to pull the air out of the system. To protect against steam entering the return main and getting into the chimney, I was thinking of strapping on an aquastat on the 1 1/4 inch line running to the chimney and setting it to about 180F. I also have some thermostatic traps I could use, but they would restrict the venting and a failure would not be easily detected. The 1 1/4 inch line is about 4 feet long, so I could set the aquastat away from the warm returning condensate. The condensate would probably be quite cool if the radiators top out at 80% full.
As a more conventional alternative, I could install two Gorton #2's on the end of the returns. If I do this I should split the supply mains and vent them separately too for best performance. Venting into the chimney would probably work better and be easier.
3) Install vaporstat and set to about 4 oz cutout.
4) Repair major leaks.
5) Delime boiler due to excessive make up water.
6) Put in header
7) Put in the proper size gas main.
8) Install orifices in radiators without original valve and /or eliminate radiators without orificed valves.
9) Eliminate 1 inch cross over pipe in 5 above and repipe the end of each main separately to the new wet return. This should ensure steam and condensate are flowing in one direction only. New boiler water line is about 4 feet below mains, so 1 inch line is unnecesary.
10) Have original valves rebuilt to repair leaks.

What do you experts think, especially regarding venting of the system into the chimney.


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  • I'd do it.

    I like the open pipe vent on two pipers, in general, especially low pressure ones like that one. The chimney draft is a bonus.

    My concern would be for the chimney itself, of course. If it has a metal liner, how would you get inside the liner. If it doesn't have a metal liner, should it have one? I'm not worried so much about the water vapor, as I am about the temperature of the liner.

    If it has stack temps like my steamer, I'd be OK with it, I think.

  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    What I figured...

    was that I could just go into the single wall vent running from the boiler over to the chimney and sealing the hole with a little high temp sealant. This gas boiler has a draft hood, so chimney temps usually are low, but the exhaust is diluted.


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  • When the mains are venting, the boiler is running the steadiest. I think I'd go for it. I'd document the stack temp, on the way out.

    On another note, I took pictures of a 2-pipe air vent system today, with original pipe radiators. I'll get the pictures up here later on...

  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    Another thought.....

    is that the boiler has a stack damper, so despite the chimney not getting hot from the boiler exhaust, the draw is pretty strong when the boiler is off. I am not sure if a water heater is in the flue.

    Two Pipe air vent system....pretty cool.


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  • I think you have it nailed

    That 1-inch pipe coming back from the ends of the steam mains is probably a vent line that eventually went back to the chimney. No mention of it in Lost Art, though, but it does say there was some sort of damper regulator/relief valve thru which the air passed on its way to the chimney. There was also a cylindrical condensate receiver that was open at the top, and had a sight glass that would show the boiler pressure based on the height of the water in the receiver. That pressure, not surprisingly, was in ounces. This is Vaporstat territory.

    So far, I don't have anything further on the ADSCO system.

    If you want to vent this one into the chimney, I'd get the biggest thermostatic trap you can find so it won't restrict air flow too much, and install this just before the chimney connection. Better yet, install vent traps on the end of each steam main (appropriately sized to the mains) and one for the dry return. And top it off with the aquastat you mentioned.

    Let us know how well it works!

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