Hughes Views #1 - Where is all the air going?

In my twenties, I spent a lot of time doing service calls in some of the tallest buildings in downtown Baton Rouge.  Some of the mechanical rooms inside these buildings are a sight to see.  They are full of heavy industrial equipment from pumps to chillers and steel piping everywhere!  Have you ever been in a large commerce building that is vacant?  It can be a bit eerie and creepy quiet.  This is the same feeling I would get when walking into a basement floor mechanical room and all the equipment would be shut down.  Now, at this point it should be said that buildings like these are not made to shut down, maybe throttle back, but never completely off. 

Every now and again, I would get a simple service call where I could walk straight to the air compressor and reset the motor starter on the wall and watch as the inner workings of the building would slowly bring itself back online.  Immediately the air compressor would kick on and begin a chain of events by sending main control air pressure (~30PSI) to all the various mechanical systems.  Just like the veins in your body, this air would travel down little black tubing or copper tubing to all the components in the mechanical room, the individual air handler rooms as well the thermostats and VAV (variable air volume) boxes.  This chain of events would begin with the chilled water pump along with the air handler blowers on the individual floors, once water flow was proven the chiller would begin its startup sequence, after a few more minutes the thermostats would build up enough main control pressure (~30PSI) to allow the pneumatic mechanical components on the individual VAV’s to begin their operation of adjusting for CFM’s.  And just like that, in less than twenty minutes, the building is back on-line, and comfort is being delivered all with the push of a button. 

Being in the presence of this is magical to watch and listen to.  It reminds me of a scene from one of the Jurassic Park movies when the power gets turned back on after being off for years and all the lights, mechanical equipment and controls begin to start firing up.  I find it interesting how so much real estate is controlled by such a small and simple means of control.  When did the shift to DDC (direct digital control) happen and what caused this rush?  I understand that there is something to be said about efficiency, but with this efficiency comes a new set of rules.  Now, I am not saying I am against DDC controls, but once you let your building be overtaken by this proprietary knowledge, it is not so easy to turn back.  I guess with anything changes must come eventually, but if you wanted that same great old reliable mechanic to be a one stop shop for all your building problems, good luck!  As most DDC software is proprietary to the installation company and will only be allowed to be touched by their trained professionals and trust me there will be a cost for this service.  Now DDC is not all doom and gloom, to be honest there are more features behind DDC that I have ever seen with pneumatics, for example faster reaction times which leads to better comfort control.  I have had building owners ask me once or twice about what the possibilities are to move away from pneumatic controls, but once they see the sticker price for the DDC upgrade, they respond with sticker shock and that conversation quickly becomes forgotten as fast as it was mentioned.  I have pondered on these statements many times before.  Is there a happy medium to be had?   Why are we wanting so bad to push this reliable technology out of the marketplace one hundred percent rather than sharing the space with it?  Who will be the select few individuals of the next generation that takes the torch from these guys? 

As I bring this story to a close, I think it is fair to explain the meaning of the title.  I thought it was a good fit because of the double meaning.  When using Pneumatics, there will be lost air.  As the damper and other mechanical components adjust, the control air will leave the device through means of a bleed port or something similar.  The second meaning behind this title is stating that pneumatics is a lost art that no one is training for!  At the time of this article I am thirty-five and from what I gather from my peers no one is being introduced nor discussing this technology.  I find this odd, because so many buildings still run on pneumatics, and will do so for an exceptionally long foreseeable future.

Meet our guest blogger, Chris Hughes of Madisonville, Louisiana is a mechanical contractor, writer, HVAC enthusiast, and co-founder of Hughes Mechanical Contractors ( ) and The HVAC Grapevine.  He also writes and hosts The HVAC Grapevine Podcast.  You can follow him by joining his Facebook group or by subscribing to The HVAC Grapevine Podcast.  For any questions, he may be reached at
25th Jul 2023 Guest Blogger- Christopher Hughes

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