2 pipe steam problem

realliveplumber

I've got a commercial customer that has a 2 pipe steam system. In the auditorium, there is an air handler, with a steam coil in it. This room was remodeled about a year ago, and there was some repipng/rewiring done on this air handler. It has, however, been working fine up untill now. There is what appears to be a regular Honeywell zone valve on the upper (supply) pipe, the lower (return) pipe travels 12" horizontal, then comes to a tee, with a 6" riser looking up. The pipe continues another foot, to a steam trap. I am told that there is another steam trap further down the line.



On the top of the 6" riser, there is a coupling, with what appears to be a bushing inside of it. There are no threads in the inside of this supposed bushing. It is open, and spewing water.



The air handler runs continuously, even with the t'stat removed. I am assuming that there is an aquastat somewhere that is calling the fan to run.



They started having problems with the fan running continuously on Tuesday, and the maintenance guy changed the t'stat, played with the zone valve, and Lord knows what else, He is pretty knowledgeable with the bldg, though. The open ended tee started spewing water today.



I gotta go back tomorrow to look at this mess. Any ideas?



Especially as to why that open ended riser would be there?



And why it would be spewing water?

nicholas bonham-carter

mysterious riser

 is it some sort of vent, or check valve to relieve vacuum?--nbc

realliveplumber

not sure

I did not notice a vacuum breaker on this arrangement. I would think it would be above the coil, though. This riser is on the return, at the bottom of the coil.  I wonder if they are using it as a vent?