mystery pipe stub??

jpf321

can someone explain why the rads in this old schoolhouse in brooklyn have a mystery stub (white 90deg elbow) near the supply valve? it's open ended. the school is 1-pipe steam. presumably this pipe used to do something else previously. any ideas? 

gerry gill

Perhaps,

the pipe may have gone thru the legs of the rads and picked up the air discharge of a Paul style vent..maybe..

Dave in QCA

Johnson control system perhaps?

Are there any signs or remants of a pneumatic control system?  Is there a non operational room thermostat, or a blank plate where one once was? Any more signes on 1/8 pipe running around the building, perhaps originating from a location where there might have been an air compressor?  

Johnson Control did use snap acting thermostats up through the 1930s. They sent 20 psi or air pressure down 1/8 iron pipe to close the radiator supply valve.  These did not operate as proportional control as most pneumatic controls do today, but rather, a simple on/off control.  When the the thermostat would call for heat, it would suddenly release the pressure from the line running to the valve operator heat, and it made a very audible hiss that lasted about 5-10 seconds.  A spring in the valve operator would cause the valve to open. 

Just a possibility.....as these systems were often installed in public buildings.

Jean-David Beyer

pneumatic control system?

They had that in my grade school, back in the 1940s. Just as you describe. They had three or four coal-fired downdraft boilers, but IIRC they ran only two or three at a time, depending on the weather in Buffalo, NY. A friend of mine had the license to run those boilers. They produced no visible smoke when he ran them, but after he retired, they smoked a whole lot.

jpf321

thanks all

thanks all for the considerations .. i won't be back over that way for a few weeks .. i'll see if I can poke around a bit deeper when I am.