No changes are permenant...

hvacfreak

I've been working in a building on a couple of floors with pneumatic vav boxes ( early Trane Plunger type ). Many have been retro'd with new KMC controllers...some are the original controller / reversing relay ( I guess that the original controller was direct reset only ). The air balance tech and building super were both telling me that I had to set up the retro boxes like the old ones ( with reversing relay ). Thier jaws hit the floor when I threw on a rev. action stat and tweaked the controller to work with it. There are some new boxes ( Trane ) that spec a reverse action stat...I said it makes sense that the retro'd boxes use rev. acting ( as many of the rev. relays had been removed ).

It's weird how calibrating the stats just make everything work right instantly. You get halfway through the floor doing this and you realize that the comfort lever has improved 10 times over.

I am a fan of DDC control systems , but this air stuff is true art ( perhaps a " lost art " ). Bi-metal strips on levers that allow precise amounts of air to pass , bags that fill with air connected to rods ( or plungers ) , valve shafts...all this stuff constantly in motion ( or at the ready at least ). I almost wish I got to do more of this stuff ,lol. And with air controls , one thing is certain.." No changes are permanent , but change is ". -Mike

Sweet vid Rick. - M

hvacfreak

...but change is

I have been working with alot of pneumatic controls lately ...and I thought of this song. Funny thing , I don't think digital controls will ever be able to modulate or proportionaly control as well as this stuff does. I mean , when you get to a device that you can " tune " ...it just feels so right ( some may know what I'm talking about ). Any way , this is a great song...

http://www.youtube.com/watch?v=C66mqA1gSrQ&mode=related&search=

edit : subject line is spelled wrong , I don't know how to change it...oh well...it's permanent for now..lol.

Paul Fredricks_3

In the center column of that page is the same song, but it just focuses on Neil Pert. It's great to watch him as he does business from his office.

Dave_4

what do you mean by

tuning pneumatic controls. Please educate me.

Dave_4

absolutely

awesome. Great video of a masterpiece.

mtfallsmikey

A double-edged sword

Yes, pneumatic controls can be awesome, also can be a major nightmare. At least in my experience,using pneumatic actuators on VAV dampers, they can be infinitly tweaked, but Johnson Controls makes a replacement for the pneumatics that is simple and a lot more reliable.

Perry_3

Agreed... But Analog electronic controls really rock

There is such a thing as Analog electronic controls. Again you could tune them for the application.

They also offer the benifit of the maximum possible cost savings due to their percision.

Digital controllers try to mimic an analog controller - and admitedely the best ones do it well enough (but not perfect).

Unfortunately, electronic analog controlls are only used in specific applications these days. While the components to build one are a fraction of the cost of a digital controller - the design hours involved for each controller far overwhelms the design hours for a digital controller that can be used in many more applications.

As such, electronic analog controllers are more expensive for the vast majority of consumer and many commercial control applications. In rare cases they still exist.

Perry

Supply House Rick

hvacfreak

http://www.youtube.com/watch?v=EUPgSOwTIAA

Here's a nice way to start the day...

Rick

BillW@honeywell

Pneumatics rock!

Great systems, if the air supply is kept clean & dry, they work "forever", and no electronic motor can equal the close-off punch of a 13" actuator. Developed in the 19th century, before electricity was available, but when buildings grew exponetially in size, the pneumatic control system was an off-shoot of the pneumatic tube systems then used for routing documents around office buildings. You can still see systems like that in some drive-up windows at banks. Steam-powered air compressors provided the air pressure, and thermostat bi-metal elements moved up or down in response to temperature changes, allowing more or less air to escape, thereby moving a pneumatic diaphragm up or down, positioned a valve or damper provided modulating control before electricity was available. Inherently safe, because unless you are switching electricity with air pressure, no sparks or electric current to worry about when combustible gases or vapors were present!

No one has ever come up with a more successful control strategy for school unit ventilators than was done with pneumatic day-night automatic control. Sadly, many of these systems have been destroyed needlessly because either no one understood how they worked, or mistakenly disabled their outside air dampers thinking it would save energy.

Parts ARE still available, and many pneumatic systems soldier on here in NJ in our office buildings & pharmaceutical plants. Any questions about them, shoot me an email.

Paul Fredricks_3

Want to see something neat?

Dig into the workings of an old player piano. They use pneumatics, but in reverse. The entire system works on vacuum, with pneumatic tubes to bring the signal to a valve chest. Volume, expression, tempo and the hammer action is all controlled by valves run by vacuum. Very neat stuff.

JJ_4

Keep the big actuators

I worked for a DDC company that installed Barber-Coleman Network 8000 controls and valves. We would typically keep pneumatic actuators for large valves and dampers, but use DDC for VAV boxes and zone valves. We would run the actuators off of a transducer with a 4-20Ma signal from the DDC converted to 0-20 psi. Big electric actuators tend to burn out quickly if someone tunes the loop so that they hunt. Pneumatic actuators "don't care".

hvacfreak

moved it down

to the bottom , and bump. lol

RJ_4

Pneumatics will probably always be around.

I have been working with pneumatic control systems since I was an apprentice in 1973. I guess I am old school, but I still prefer pneumatics over DDC. As a U.A. Instructor I am finding the pneumatic class is a favorite of the apprentices. Alot of the older buildings are still working great with pneumatic controls.. A little calibration and oil/moisture free air and your system should last for years.