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Manufacture recommended piping - one riser or two.

The recommended piping on a CAC-BDP BS2A boiler, shows using 1 riser or 2 risers, but does not explain what should govern the choice of either one. The 2 riser example shows 2 1/2" riser and 2 1/2" horizontal. Where does the wet and dry steam separate? I am considering making the horizontal a 3" with a 3" rise to the main with a reducing ell to the main steam line (one pipe, parallel flow) 2 1/2". It should also be noted the 2 1/2" main runs about 6 feet, then splits off to 2 mains, one remains 2 1/2" and the other is 2". Both returns are 2" drops at the boiler. This boilers existing piping arrangement is fu-bared, and I am going to re-pipe it. Should I brake away from the recommended piping, or follow it? Also, what in the world determines 1 riser or 2 risers, when the manufacture leaves that choice to the installer? with no numbers to help the installer make a choice. The other thing I found strange, the Hartford loop into the equalizer is shown to tie-in 6" below the water line, not 2". What-up with that? This is a 187500 BTU residential boiler. The attachment is the 2 riser drawing.


  • ProblemSolverProblemSolver Member Posts: 190
    SWEI: 150,000 BTU out is about right; and NO, I am not changing the main steam line layout, I am only interested in the near boiler piping to get 100% dry steam out to the steam mains.
    Abracadabra: the 6" would lead me to believe they think the water level jumps aggressively in their boiler, no other reason for such a distance. That's my take anyways - anyone with more ideas.
  • ProblemSolverProblemSolver Member Posts: 190
    The most important thing here is my wanting to increase the horizontal pipe (off the risers) to 3" and then rise to the 2 1/2" main steam line with 3" and connecting with a 3 x 2 1/2" reducing ell. The change to 3" should give me what is needed to keep wet steam out of the mains. Or is the manufacturers suggestion adequate?
    Thank you for your response guys.
  • SWEISWEI Member Posts: 7,356
  • ProblemSolverProblemSolver Member Posts: 190
    SWEI: holly smokes, that link is a whole new can of worms for me. I'll have to look at it later, but I am not trying to re-design the whole system, just the near boiler piping. This is the re-pipe I am dealing with.
  • SWEISWEI Member Posts: 7,356
    This is high season for the heating business, so the real steam pros are probably out in the field. tells me that at 1 PSI, the steam in your 2-1/2" main will be moving at nearly 33 feet per second. I would seriously consider bringing both of those mains back to the header if at all possible.
  • JStarJStar Member Posts: 2,752
    I would absolutely use two 2-1/2" boiler risers into a 3" (borderline minimum) header. A 4" header would be better, but might not be necessary. All of my charts are based on 1psi of pressure. If you are running on a Vaporstat, the 3" header will be okay.

    As for the main...if it's 2-1/2", then it won't do any good to feed it with a 3" take-off. You could install a 10" x 2-1/2" reducer and still have no benefit. The main size is all that matters. And it needs to be 2-1/2" all the way back to the header.

    Is this also a counterflow main with a drip return?
  • JStarJStar Member Posts: 2,752

    SWEI: holly smokes, that link is a whole new can of worms for me. I'll have to look at it later, but I am not trying to re-design the whole system, just the near boiler piping. This is the re-pipe I am dealing with.

    A steam system is a...system. You cannot replace a boiler without thinking about the entire system.
  • ProblemSolverProblemSolver Member Posts: 190
    Jstar: It is a parallel flow with drip returns.
    I am re-piping the boiler because the mrs. wants an auto feeder and the water inside the boiler jumps so radically I refused to install it. I am the second tech telling her the piping, as-is, is trouble.
    I lost my total EDR sheet, but the boiler is large enough to effectively handle a cold start up, and slightly over sized for the middle of winter.
    I hear what your saying! I do look at the entire system for important points, but I do not re-engineer it then compare that to what is actually there. I do that kind of thing with force air, but I have never engineered an entire steam system (header, risers, vents, etc.) to double check the original engineer's design. Here in the northern suburbs of Detroit, we see 3 or 4 steam boilers a year, and replace one, on average, every 3 years; mostly because of dry firing. Not a whole lot of opportunity to maintain knowledge, so I do a lot of reading this time of year.
    I 100% agree with you, both steam mains need to come back to the header - thanks for that!
    My concern about the 3" header had nothing to do with the amount of steam being delivered; it was all about giving the wet steam a place to drop out before entering the 2-1/2" main.
  • JStarJStar Member Posts: 2,752
    Proper near-boiler piping will prevent the production of wet steam. Save your time and money on the riser. Although, threading and installing 2-1/2" pipe is about the same effort as 3".
  • ProblemSolverProblemSolver Member Posts: 190
    Thanks fellas, I am all set. Thanks for your time!
  • vaporvacvaporvac Member Posts: 1,520
    Perhaps you could do a drop header while you're at it to ensure even drier steam. JAHO here, but that seems to be the preferred way.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
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