One pipe steam problem, Ideas Guy's.

tim smith

Got a one pipe over head feed in 12 unit building. Goes up 2 stories from boiler, across ceiling to opposite end of building, drops down wall to basement radiator. Picking up a few radiators along the way. Picks up last high wall radiator in basement unit and then runs along floor back to boiler room. 2 new #75 hoffmans on this return line in boiler room. 1 # 75 on other return which comes from above but on same side of building as boiler. #  40 vents on each radiator. Problem is, the basement radiator mentioned never gets hot. The main drop will get  hot but pretty slow to get there. The boiler was being run at 1.5 psi off .5 on. Tried raising a bit to see if this would help, I know, usually not but......, our tech thought was faster but does not seem so. F&Ts on end of each return then to feed pump. Pitch or return is marginal but present. Removed union at rad to see if water backed up, not. When boiler under pressure our tech even removed air vent on basement radiator, drop was hot but just getting moderate air out of vent hole on radiator but no steam. Frustrated, confused, looking for cliff.  I am sure it is something we are overlooking but......       Tim

nicholas bonham-carter

overhead feed

does that mean that the steam travels from the boiler straight to the top floor, and then begins feeding radiators from top to bottom? if so that route is twice as long as the conventional feed, and therefore needs even more main venting. for a start, i would put a gorton #2 along side those hoffmann 75's, if not several.

with not much air movement when you take off the vent on the lowest radiator, i would suspect a sag in some horizontal, trapping the condensate, and preventing the air from escaping. when firing, does the top radiator have air coming out when the vent is removed?  maybe if the trap guts are temporarily removed, you will see more pressure down in the return.

this would be an ideal use for an ir camera, to see where the steam gets held up. . if the pigtail is plugged, then the useless 0-30 gauge would only show a tiny bit of movement, while the traps and vents were rendered inoperative by over-pressure. that sort of system should get steam to all radiators with only a couple of ounces of pressure. it might be time for a good low-pressure gauge [gaugestore.com 0-3 psi].--nbc