1 pipe steam ???

tim smith

Hey guy's, old 1920s bldg, 1 piper. Radiator vents. 4" main up to attic, branches off and down through 4 branch drops. No main air vents in attic. Just rad vents and F&Ts down in boiler room where drops come back. ?? no signs of where main vents ever were up in attic. Cannot see any other place. Think it would be a good idea to add main vents up in attic?? Just looking for some input. Trying to figure what original intent was on system. Thanks in advance, Tim

ttekushan_3

No.

That was the short answer! The returning steam lines that appear in the basement are in fact the end of the mains. The vents in the boiler room are end-of-main vents. Its just a bit confusing since they are so close to the wet returns in the basement. The long length of the mains is offset by the short returns.

The fact that its an overhead system indicates that the condensate, air and steam are all running in the same direction in parallel flow: down. So the condensate and air really charge to the basement to get out of the steam's way. Whats also great about these systems is that if you have a number of separate end-of-mains/condensate returns, you can proportion their venting rates right from the boiler room in order to better balance the system.

EDIT: I'm thinking about those F&T traps. I certainly hope they are draining/venting into a DRY return. Is there a vented receiver/condensate pump arrangement there? If those traps "vent" into a wet return thats probably why you're asking about extra venting. The mains are air bound, venting only through radiators giving you a cold first floor especially on the ends of the building. If this is the case, take one of the upper plugs out of each of those traps (if they have them) and install a main vent on each one. This allows condensate to exit through the trap as usual and allows the air to exit through the vent.

-Terry