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Loop seals vs. F&T traps on 2 pipe mains

delcrossv
delcrossv Member Posts: 2,168

Is there some reason why 2 pipe mains are crossed over to the dry returns with F&T traps rather than a loop seal for the condensate and a thermostatic trap on the top for air?

Seems a loop and TS would be a lot less maintenance.

Am I missing something?

Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.

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Comments

  • Steamhead
    Steamhead Member Posts: 17,789

    What "system" is it? (Webster, Dunham, etc)

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • delcrossv
    delcrossv Member Posts: 2,168
    edited March 10

    Just a general low pressure 2 pipe system.

    Probably closest to a Dunham -rads are trapped, vents at ends of dry returns etc. Sufficient B dimension for up to 1.5 psi.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • Jamie Hall
    Jamie Hall Member Posts: 26,007

    You're not missing something. The combination of loop seal and crossover trap is much cheaper and simpler — and considerably more reliable — and offers higher capacity than an F&T.

    However.

    It this condensate path is a loop seal to the dry return, as it sometimes is, it is limited to relatively low pressures. Even if the loop seal is a generous 60 inches, any steam main pressure over 2 psig will allow steam to blow through the loop seal and pressurize the dry return. This is not good.

    Now if the loop seal isn't really a loop seal, but consists of two drips (one from the main, one from the dry return) going to the wet return, this limitation doesn't apply — but… now if the boiler pressure acting on the wet return will raise the condensate in the wet return up to the dry return if the pressure is too great — using that 60 inches, 2 psig again.. This isn't good, either.

    So. Bottom line: if you boiler pressure is much over a couple of pounds, you are going to need an F&T. Otherwise, you're better off with a crossover trap and a loop seal or double drips.

    Note that an F&T makes a truly miserable main vent — so you'll need a main vent at the end of the steam main.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    delcrossvMad Dog_2
  • Steamhead
    Steamhead Member Posts: 17,789

    Does it have any original traps and rad valves? If so, what make?

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    delcrossv
  • delcrossv
    delcrossv Member Posts: 2,168
    edited March 10

    Saw a couple of Mepco, that made me think Dunham. Would that make a difference?

    Pretty well butchered otherwise.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,786

    Only problem with a loop seal is if someone jacks the pressure up. Other than that, more reliable than a trap.

    delcrossvMad Dog_2Long Beach Ed
  • delcrossv
    delcrossv Member Posts: 2,168
    edited March 10

    Should i provide a tee or something to prime the seal? Guess I'd only have to do it once,as long as the pressure is controlled.

    Or just wait for it to fill? What's SOP for these?

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,786

    It will fill as soon as it runs. No need for a tee.

    mattmia2
  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,158

    For the 1874 AA Griffith's two pipe radiator in our parlor, I made a loop seal below in the basement because I wanted to keep my New (2001) Vapor system extremely simple , no traps to confuse some guy many years from now. I will post a picture. Mad Dog

  • delcrossv
    delcrossv Member Posts: 2,168

    Very Nice! The top sillcocks are for flushing? How often do you need to do that? @Mad Dog_2

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,786

    @Mad Dog_2

    Don't worry.

    The loop seals will confuse them more than a trap.

    LOL

    Remember I drive a truck with a mellenial anti theft device. A 5 speed.

    delcrossv
  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,158

    Nah Ed…a loop seal is a basic plumbing P Trap..very obvious what it does even to the dopiest plumba...I've seen countless very good plumbers having no clue what a steam trap actually does. Mad Dog

    delcrossv
  • delcrossv
    delcrossv Member Posts: 2,168

    Ever need to flush it?

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • Jamie Hall
    Jamie Hall Member Posts: 26,007

    shouldn't have to… but it does no harm to plumb it so you can.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    delcrossv
  • delcrossv
    delcrossv Member Posts: 2,168

    Seems @Mad Dog_2 went to great lengths...😮

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 12,741

    I need someone like @Mad Dog_2 if I ever replace the orangeburg under the street because I want someone to dig the joint out of the clay main branch and caulk PVC in to the clay and put a fernco over the hub and pipe as a second seal and I don't know who will do that in Michigan.

    delcrossvMad Dog_2
  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,158

    I'm reeeel good at The Low-Iron...

  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,158

    I flush every few seasons..mad Dog

    delcrossv
  • JohnNY
    JohnNY Member Posts: 3,317

    I'm on a job this week where ¾" radiator steam traps were added to the existing loop seals. It's a monumental hack job and I'm trying to convince the management company that they did a bad thing hiring the company that added the traps especially in light of the fact they have a directive from an engineering company to replace them and proposal from a plumbing company to do that work plus add F&Ts (their idea) where they don't belong. It's remarkably terrible on many levels.

    Does anyone have a clear photo of an original loop seal they could share? I'm having trouble finding one and I would like to include the picture along with the thousand words it's going to take to reverse this course.

    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    delcrossv
  • delcrossv
    delcrossv Member Posts: 2,168
    edited March 30

    @JohnNY

    Into a wet rather than dry return, but hope it helps.

    bxj0m9th10ks.png
    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • JohnNY
    JohnNY Member Posts: 3,317

    @delcrossv Thanks a lot. I saw that in the archives but it's likely to be too confusing to the client since it's not in the dry return.

    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
    delcrossv
  • Steamhead
    Steamhead Member Posts: 17,789

    @JohnNY , here is a discussion of the Tudor system (which became popular in Europe), using these loop seals. On page 5 of the PDF there is a diagram showing one:

    Site faviconEuropean Heating Systems in 1907

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • JohnNY
    JohnNY Member Posts: 3,317

    @Steamhead That’s fantastic, Frank. Thanks a million. Hope all is well with you.

    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
    Classes
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 17,786

    Why would you need a loop seal to a wet return? Just askin?

    delcrossv
  • delcrossv
    delcrossv Member Posts: 2,168
    82beef69-a120-49fc-8e7b-20e36668690d.jpeg

    2 pipe air vent with loop seals on the rads.

    Site is on the top.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • delcrossv
    delcrossv Member Posts: 2,168

    Wet return doesn't stay wet? Odd.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • Mad Dog_2
    Mad Dog_2 Member Posts: 8,158

    Installed on my Vapor system around 2002. Radiator outlet enters loop seal on the left...Mad Dog

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