Two pipe problem

Unknown

If the 2 pipe rad dry returns, drop into a wet return at some point near the boiler, then you will see a vent as you describe, at the end of the dry return. In Dan`s book LAOSH, it`s discussed on Pgs.126-7.

Tony T

Two pipe problem

Looked at a house today, about 4000 sp.ft. that has a two pipe steam system with various traps (barnes & Jones, mouat, ect.) and #75 main line vents at the end of the dry returns off the vertical drop about 12" down, to a tee, then back up above the main. I have 3 questions,
1) Is the placement there to protect the vent?
2) All the radiators have #40 hoffmans, how is this working? I thought there should be no radiator vents with traps.
3) Would it be better to operate with a vaporstat at 4 to 8 ounces instead of running at 2lbs. Hope you can help!

gerry gill

oh boy,

you have your work cut out for you..the main vent placement is fine..much better there for protection of the vents than at the end of the main..you mentioned mouat..are you around cleveland? so am i if you need to talk about this..people put one pipe vents on two pipe radiators when they are trying to get them to heat better..they are treating the symptom tho, and not the problem..the steam main and return main vents should have been looked at first, then the radiators traps,,if then the radiator doesn't heat, then the inlet valves should be checked..if its open, then there is a sag in a return line if the radiator worked with the air vent on it..the sag should be fixed..the vents on the radiators removed and plugged..the problem with putting a radiator vent on a two pipe radiator is two fold..first, someday that traps gonna fail closed..the vent will still let the air out tho, so the steam will come in..it will of course condense..the radiator will start to fill up..the boiler will miss this water and call for the feeder to give it more..eventually the water will leak past the trap and come back to the boiler..now the boiler floods..or..just as bad..the radiator fills up with water and no longer heats..you get called to fix the trap..you remove the cover expecting it to be dry and dump 5 gallons of water on the hardwood floor..which proceeds to go thru the hole the pipe is using and drench the ceiling below..all cause some jerk put a vent on a two pipe radiator..and yes those two pipe systems are vapor systems and should run a just a few ounces.

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Christian Egli_2

Oh, and ask about the TriTube

Everything Gerry said. All I'll ask further is if you are considering returning this system back to a live Mouat? Not a crazy idea by the way.

Or else to a standard two pipe atmospheric return with radiator traps. In this case, the mix of the Mouat (if the non thermostatic type) and the modern standard thermostatic traps is probably not beneficial. So... if you're going to remove the leftover Mouat, can you think of getting them to Gerry for venting analysis. Pretty please,

Was there ever something like a TriTube where the 75 is now? they don't work the same way, the 75 is probably doing more harm than good.

2 PSI is too much. Two pipe atmospheric returns can't handle much pressure, namely the stacking B dimension. This could be a cause of the flooded returns. You don't need 2 PSI anyways, and if you really really do, then you'll need a pumping scheme on the return condensate.