name that gizmo

jpf321

I was on a walkthrough at a NYC Public school today (for my daughter to attend, not for steam reasons) .. but being ever vigilant, one radiator stuck out as different from the others .. the whole building seems to be 2-pipe steam .. with this gizmo on at least one rad ... I'm guessing it's one of those pneumatically operated valves that was discussed here in the fall.

crash2009

I was wondering too

  I have seen them at the courthouse here in MI.

Jamie Hall

I'd bet...

you are right -- look at the small tube going into the housing.  Probably from a pneumatic thermostat somewhere.



The thing would probably work fine, given a little TLC.  Which I'll bet it hasn't had in decades...

DanHolohan

Yes,

that's what it is. Good eye!

Dave in QCA

Pneumatic Control Valve it is!

Great picture of a pneumatic control valve.  It looks like it is a replacement, but the system was probably there very early.  Note, it appears the neoprene air line is connected to an 1/8 iron pipe behind the radiator.   I can absolutely say that this is not a Johnson Controls product, pretty darned sure it is not Honeywell either.  My guess is that it is a Powers Controls valve.



You can see an exposed spring beneath the control heat.  It causes the valve stem to slide upward, to the open position.  Air pressure is introduced into the control head and pushed against a rubber diaphragm, which in turn pushes against a metal cup shaped devise, that pushes down on the head of the valve stem.  Usually the spring is sized so that at 4 oz of air pressure or less, the valve is fully open.  As the air pressure is increased above 4 psi by the thermostat, the valve will modulate closed.  When the pressure is at 8 psi or greater, the valve will be fully closed.



These systems seem to be a mystery to most folks that do not work on them, but in reality, they are pretty simple, very reliable, and do a fantastic job of providing room-by-room control in a large building.

jpf321

well as I mentioned ...

This was only on 1 of about 40 rads that I spied during my tour .. unknown whether it is actually operational. I should also note that several rooms, including the very well radiated cafeteria had their windows opened :-( ...  I wish we could just fix/optimize all the steam systems in the world, maybe we'd save some significant fuel.... http://www.heatinghelp.com/forum-thread/135599/some-savings-to-report



FYI, the school just celebrated 85yrs old.

Jean-David Beyer

My grade school had these, one on each radiator.

Each radiator had one of these. Two pipe system.  This valve put steam in at the top of the radiator, and the condensate went out at the bottom at the other end. My recollection is that the valve was about 5 inches across, but I was a kid then, so it may have been smaller. We definitely had pneumatic thermostats that hissed when they opened, but pretty soon after, the steam hissed even more until the radiators filled. Then it quieted down. I imagine the steam pressure for that school was higher than would be used in a home.

Dave in QCA

Old Style 2 position T'stat

That would have been an old style, 2-position thermostat.  They did not put out a modulating pressure.  The mechanism was a snap acting device that either put full air on the valve actuator to hold it closed, or released it (thus the hiss) to let the valve open.

My guess is that the steam pressure was maintained at 2 PSI, althought it could have been as high as 5.   When you open a valve to a cold radiator and there is already 2 PSI of pressure in the line, it will make a pretty good steam sound too.

clammy

Seen similar

I have seen these on steam supplies and i have also seen them built into the retrun traps in conjunction with the steam supply valve.It was very ingenius the way they worked ,as the pneumatic controller called for heat it would direct air pressure to the steam control valve opening it as condensate forms and the trap starts to open a linkage opens and discharge the air pressure and the steam control valve slowly closed as the trap closes the valve opens again.This set up was in a large home with a large air handle and 3 - 2 pipe steam coils all the controls where pneumatic on the steam side for controlling the coils .It was pretty cool stuff the rest of the house was a original mix of 1 and 2  steam ,no condensate pumps either.The boils where some old hb smith ,the home was built in1903 or so ,i believe it was about 15000 sq ft the boilers burner 18 gph very ool stuff peace and good luck clammy

Owen

Pneumatic Bonnet Steam Valve

There will be an air compressor somewhere, probably in the basement. When it fails for some reason everything is fully open so it gets hot in all the rooms fast.

Dave in QCA

VERY HOT!!! VERY FAST!!!!

Yes, in almost all pneumatic setups, the system is designed so that if it fails, it goes to full heat.  For A/C, it fails off, fresh air dampers fail closed.