two pipe steam, 3 basic questions

iddelz

thanks to dan's books and many people here, over the last two years, I've gotten my residential one pipe steam system humming along smoothly. now a v nice rabbi in brooklyn (*) found out i'm handy and asked me to look at their synagogue boiler. its a two pipe steam system for a three story building. i'm not familiar with 2-pipe but i noted some obvious problems i'm wondering about ...



1) pressure is running around 30PSI according to the gauge on the boiler (which may or may not be right). this seems woefully inappropriate but wanted to know if the rules about lower pressure differs for larger 2-pipe systems



2) the system is wired with both an additive pressuretrol AND a subtractive pressuretrol. I can't imagine how this makes any sense. also the subtractive pressuretrol has no setting for the differential (see picture below). is there any reason to have both, and particularly one that's broken? I'd think this explains the high pressure, since there seems to be no sheriff telling the boiler to stop.



2.5) also neither pigtail that feeds the pressuretrols seems to get hot, indicating to me that there's probably something clogging them and need to be replaced or unclogged. is there a way to unclog these (vinegar or something?).



3) finally there's a return pipe coming out of a wall that just spits out steam when a cycle ends. it doesn't connect to anything. v strange.



my experience with most institutions - coops, schools, etc. - is a general lack of functioning maintenance and knowledge about heating systems. i've already gotten them to address the first issue, which was the smell of gas every time the boiler started, (a plumber came and replaced the relay, but he said wasn't a steam expert as i'm told). i'd like to fix the little things and get a plumber in after the heating season to refine the system but it would help to better understand these simple things in the meantime.



thanks / iddelz



(*) a rabbi walks into a bar with a frog on his shoulder. the bartender says "where'd you get that?" and the frog says "brooklyn! there are thousands of them!"

BobC

Gauge broken?

I'm no expert on two pipe steam but here is my take on your problems.



Is this is a low pressure steam system and not a vacuum system? If so it should be operating below 2PSI.  At 30PSi the pressure relief valve would have gone off and the boiler room would be full of steam. I suspect the pressure gauge is now a paperweight. A working pressure gauge should be installed and I would recommend a low pressure gauge as well so you can see what is going on.



For safety reasons pressuretrols can be wired in series so having one fail will not leave you without a pressure safety. That pressuretrol in your picture is a manual reset type where you have to push the red buttong to reset it if it ever trips. That one is set at 10PSi, what is the other pressuretrol set at? If possible the two pressuretrols should be on different pigtails on different boiler ports so no single clog can compromise the system.



The pigtail on my boiler doesn't get hot for a a long time, the water seal in the pigtail keeps the steam out but eventually the tubing gets hot because it conducts the heat from the boiler. If you have any doubts, the pressuretrols  should be unwired and removed so you can make sure the pigtails are clean; also check the bottom of the pressuretrol fitting is clean and you can see the small hole at the base of the brass fitting.



Bob