old Powers pneumatic thermostat question

gerry gill

In the pictures my screwdriver is pointing toward a lever. Whats it do, or is supposed to do?

Steamhead

Might be

to shift the unit from night temperature to day temperature. I've seen systems that had this feature, not sure how it worked........

JaredM

That's an oldie......

It looks like a night mode override lever found on dual mode pneumatic stats, but most dual mode stats have two setpoint dials.  I am not familiar with that stat.  Many pneumatic systems went into night mode (setback) by raising the system pressure to a higher level which triggered the stats to enter setback.  Way back each maker had a certain pressure they worked at....and they were all a little different, just because they could be.  The lever was used to override the thermostat back to occupied day mode.

EBEBRATT-Ed

stat

i agree probably a day/night setback stat. if you follow the air line back to it's source you will probably find two air pressure regulators piped in parallel each with a solenoid valve for each reg.. A time clock switched the solenoids on a day night basis. The air pressure regulators were set at different pressures. 20 psi day -15 psi night or whatever the manufacturer required. It is slightly different between control mfg, Powers, Honeywell, Johnson, Barber/ Coleman

RJ_4

t-stat

I used to work on old peumatic systems and was a U.A, instructor,   if you give me the mod. number I may have the old cut sheet.  As everyone has said it is most likely a day/night t-stat,  look close for a smaller dial with 0-10 degree marking  this would be the degree of night setback, as Ed said dual prv's would change air press.to t-stats.  These types of systems are still being used in some old bldg's

gerry gill

Thanks guys,

i'll delve deeper into looking around.