Loop seals vs. F&T traps on 2 pipe mains
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?
Comments
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What "system" is it? (Webster, Dunham, etc)
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting0 -
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.0 -
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
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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
Consulting1 -
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.0 -
Only problem with a loop seal is if someone jacks the pressure up. Other than that, more reliable than a trap.
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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.0 -
It will fill as soon as it runs. No need for a tee.
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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
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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.0 -
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.
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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
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Ever need to flush it?
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.0 -
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 England1 -
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.1 -
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.
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