two pipe gravity return?

snickerdoodle

I'm working on a two pipe steam system that has a condensate tank with the "classic" master trap on all return lines going into it. They also put Hoffman #75 air vents before the traps. The radiators/baseboards have airvents and steam traps on almost all of the floors, Although some have no steam traps and some have no air vents. The main problem is with the 6th floor in one apt. someone feed radiators with an exposed 1" line that is run counterflow of the steam (pitching up to the radiators) with steam traps on all radiators with air vents on each radiator. I know this is breaking all the "two pipe" steam rules but the system sort of works except the 6th floor. The risers run 2 1/2 horizontal in the basement and then run 2" vertically too the floors. The return riser is 1 1/2  which makes me to believe that this may be an old gravity return two pipe system based on the return size which is why the system sort of works??? The 6th floor has no heat.Plus the feed risers are dripped with a thermostatic trap not a F&T. although they allowed for more than 5" from drip to trap. The 6th floor is the top floor .

Jamie Hall

At least...

someone put vents before the traps going to the condensate tank... that's something.



Amazing what several generations of meddling with a steam system can do, isn't it?  One almost doesn't know where to begin.



Based on the assumption that you have a copy of The Lost Art, I think I would start by examining the system closely and figuring out what the original installation was like, and then set about getting back there.  Problem is, of course, that it's winter (naturally) and you do want to keep heat in the building...



First question I would have is did the returns and drips all go to wet returns, or did some of them go to dry returns?  The presence of traps on many of the radiators suggests dry returns (watch out: that condensate tank may have converted what were wet returns into, effectively, dry ones -- almost sounds like it); otherwise, they probably wouldn't be necessary.  On the other hand, those radiators without traps need to be looked at closely -- what do they return to?



The air vents on the radiators won't be necessary when the system is brought back to what it should be; in the meantime they probably will do no harm.  This does, however, sound like a system where I would seriously consider adding top of riser vents.



Nice of them to drip the risers -- but the traps should be F&T, as you note (this also suggests dry returns, by the way).



Do the traps on the radiators work?  Is there a possibility that steam is getting into the return from that sixth floor apartment that doesn't work?  Or is that return shared with other apartments that do work?



That's all I can think of right at the moment -- brain fade.  I'll think about the whole things some more.

snickerdoodle

More info

Thanks for the reply, I will have to back but as everything else these days price to fix is a big factor. The building is down on Hudson st. in N.Y. and when I do I will post all new information. By the way almost all the dry returns pipe in the basement are new. The condensate tank is less than 20 years old and it seems fairly obvious that a lot of work was done to try and fix the problems on the system. To make maters worse someone bypassed the heat timer in the basement and now a thermostat in the 4th floor hallway controls the heat in a locked box.

Jamie Hall

Does that sixth floor apt.

have its own return?  If so, one of the first places I would think to look is is steam getting into the return somewhere?  Bad or missing trap.  That will shut down a riser/return combination as effectively as closing the valves!  Remember that on two pipe steam with dry returns everything has to have a way to prevent steam from getting into the return!  Some vapour systems do this with orifices; some do it with calibrated valves; some do it with various contraptions in the outlet elbow -- but most do it with a thermostatic trap on the outlet.  Of every radiator or other steam using device.  If even one of those traps is shot -- problems.



Then you also need the F&Ts on any drips which go into a dry return (but not into a wet return).



However, you only need one trap on each path!  If everything going into a dry return is trapped, for instance, you don't need another trap where the dry return drops into a wet return or concensate tank.



Yeah, cost is always a problem.  But it's usually cheaper in the long run to do it right than to kludge it.  Sometimes hard to convince the management of that.