two pipe steam ... 3 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 my v nice rabbi in brooklyn (*) found out i'm handy and asked me to look at the synagogue boiler, a two pipe steam system - which i'm less familiar with - 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 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) 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.



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 wondered if someone can comment on these simple things in the meantime.



thanks / Avi



(*) 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!"