air controls???

Timco

I looked at a large old indirect I am removing Monday earlier and noticed it is connected to an air block, which eventually gets back to an air compressor in the mechanical room. Is this a control? can I just plug off the small air lines that lead to & from the tank? What did they do? The building is 60's - 70's era.

Tim

Mike T., Swampeast MO

Yes, likely a proportional, pneumatic control system. Any strange old wall thermostat(s) connected to the air system hanging around? Operation is very similar to TRVs in that the further air temp is below setpoint the wider a valve will open thus allowing more water to flow. Many were dual-pressure systems that allowed for unattended, automatic setback or even automatic changeover for later combined heat/cooling systems.

Am fairly certain that normally open valves were used for space heating only systems so if the air failed, you'd get full flow. If the compressed air system has been disabled, I suppose you could just remove. Johnson Controls (and perhaps others) still make components for such systems if you need to repair or get it working again. The very first proportional system I saw was built in 1899 and used components from Johnson Electric. The thermostats were utterly amazing. The internal gears had beautiful engraving like fine pocket watches.

These were very good, accurate systems but do require the extra maintenance of the compressor. It's also VERY important that the air stay dry. From what I've read failure to maintain the air drier caused the most problems.

Plumdog_2

pneumatics

Mike covered the subject well. You need to investigate further before disconnecting or plugging, to determine whether or not the pneumatic control is still in use.
We used to service air compressors and driers that fed these systems, many of which controlled fifties and sixties-era hydronic systems. There were outdoor reset devices with hand-drawn curves on graphs, and they were calibrated with sets of low-pressure guages. The original systems had carefully crafted copper-tube piping, which gave way to plastic later in the eighties.

Unknown

Pneumatics rock!

They started when buildings began getting bigger after the Civil War. Most big buildings had pneumatic messaging systems (like those in the drive-in bank window) powered by those magnificent old steam-powered air compressors. Hand valve technology was pretty useless on multistory buildings, and electricity was not available yet, so the compressed air was used as a power source. Pneumatic controls modulate, are intrisically safe (unless you are switching electricity with them), and were the choice in explosive atmospheres. A bimetal raises or lowers a flapper against an orifice in response to temp changes, allowing more or less air to escape, causing a rubber diaphragm in the valve or damper actuator to inflate or deflate, opening or closing a valve or damper. These systems reached their zenith in the 1940's, and still are in use today. Honeywell makes and sells all components, under the "Honeywell Direct" name. Commercial-oriented distributors sell them, too. The controls were updated in the 1980's,and still can be used for OA reset, space temperature, ventilation and humidity controls. Like Mike said, dry air is the key to a smooth operating system. The pneumatic control system is one of the most elegant mechanical controls ever made. I would be happy to answer any pneumatics questions anyone has.

Unknown

Powers

Powers Rock

Timco

I just plugged the air line that came to that indirect. It is a large steam heat system with 2 large turbines and 2 tanks. The tank is now 75% out. There was 1" or more of sediment on the bottom...had to shovel it out. Seems the compressor runs a lot. (electric, pretty new)

Tim

Plumdog_2

Pneumatics at Chuck-E-Cheese

Just remembered I went "backstage" at Chuck-E-Cheese one time to see what makes the Gorilla Drummer move so cool. Pneumatics! Looked like components borrowed from HVAC.

mtfallsmikey

Another..

Siemens is also into penumatics.

don_185

I work

I work with penumatics for years and I still think it the best way to control.

mtfallsmikey

And..

I whoosh my spalling wer butter!