Control Technology; A Glimpse Backward and Some Thoughts on the Future

Earlier this week, while deploying loggers to monitor filter performance in the Kaiser Building in downtown Portland, Oregon, I noticed that the original building control panel was still in place in the current engineering office/control room as illustrated below.

Old panel 01

This building, and the control panel, date back to a point in time (1970’s) when direct digital controls (DDC) were not in the mainstream in the commercial buildings industry, although the technology could be found emerging in the process control industry.

Instead, control systems were built up from discrete pneumatic and electric control elements, typically mounted in panels located near the equipment served. Remote command capability, indication and annunciation were provided at a central panel similar to the one pictured above.

When properly installed and when given enough attention, these systems actually worked and provided a reasonable, if not totally accurate indication of what was going on in the facility.  This was the “big building” control technology that I was first exposed to when I entered the industry in the mid 1970’s , and at the time it was a bit,overwhelming. The pictures below, which are the front and back of the first section of the panel, might give you an inkling of why.

Old panel 02

Old panel 10 sharpened


The device in the back view in the bottom row of components with the black knob on top is a time delay relay manufactured by Agastat that created a time delay by metering air through a variable orifice.  In current technology systems, this function is accomplished by a line of control code or a block in a graphic program;  same concept, different, more reliable, more robust, and more flexible implementation.

The next two pictures are the front and back of the 2nd section of the panel.

Old panel 03

Old panel 09 sharpened

The round gages are actually air pressure gages that are calibrated in degrees F or similar engineering units.   They are served by one pipe transmitters that generate an analog signal that varies from 3 to 15 psi as the sensed variable varies over the range of the instrument.  In current technology systems, we have digital gages that are calibrated in degrees or similar engineering units and are served by transmitters that generate an
analog signal that varies from 4-20 milliamps, 2-10 vdc, etc. as the sensed variable varies over the range of the instrument;  same concept, different, more reliable, robust, and compact implementation.

Last but not least, here are  pictures of the front and back of the third section of the panel.

Old panel 04

Old panel 12 sharpened

The large sliver dials with black lettering and red pointers are time clocks.  The dials
rotated, in this case, ,once every seven days.  Movable cogs on their perimeter (you can see one at about the 5:30 position on the top dial) tripped a lever and changed the state of the contacts controlled by the time clock, thus implementing a schedule.

In current technology systems, this function, like the time delay function, is accomplished by a line of control code or a block in a graphic program; same concept, different, more reliable, more robust, and more flexible implementation.

Part of what was overwhelming for me when I first encountered a panel like this was the sheer volume of devices, components, tubes and wires. The other part was realizing that they were all connected to something (at least in theory) somewhere in the 500,000 or so square feet of building served by the panel, and the problem I had been sent to solve probably had its roots somewhere in that maze of stuff.

As Jesse Miller (the Kaiser Permanente Maintenance Assistant I was working with) opened the back of the panel up for me so I could take the photos you are looking at, he commented that the guys that worked on this equipment really had to know their stuff. And, while that is true, it is also true that the folks  working with modern day control technology (that’s you and me and Jesse to name a few) also need to know our stuff.

The fact is that the fundamental physical principles behind our HVAC systems are just about the same as they were when the control panel pictured above was fabricated and installed. And, to properly control HVAC systems, you really need to have an interest in and an understanding of (or at least a desire to have an understanding of) HVAC principles and theory.

A computer genius today, faced with “hooking up” a control system with lines of code, who has no knowledge or interest in HVAC, will fare no better than a master pipe fitter or electrician  with with a similar outlook would have fared in days gone by when confronted with the maze of wires and tubes you see in the pictures.  The reality is that there are
computer based control systems out there that have not been properly installed, verified and maintained which are just as dysfunctional and inaccurate as the big control panel could be if it was not properly installed, verified, and maintained.

And they can be just as challenging and intimidating, if not  more so, to troubleshoot and repair.  At least with the older stuff, you could get your hands and eyes on the stuff in side the box.  With DDC technology; not so much, especially if you don’t have  the appropriate service tool and software.

It’s also interesting to contemplate that all of the overwhelming complexity that is so evident in the maze of wires, tubes and components that are inside the control panel I photographed are also present in our current technology control systems. Much of it is in the form of the software based control logic that manipulates the inputs and outputs  which still are often a maze of wires and tubes).

The fact that you can’t physically see and put your hands on the software and the fact that it has no moving parts has the advantage (or disadvantage) of making properly (or improperly) implemented strategies persist once they are set in place. It also makes corrections and modifications readily achievable; simply a matter of a few key strokes and mouse clicks.

But, these same attributes can also become detriments when it comes to fixing things when something goes wrong. Solving problems that exist in things that you can’t see and touch can be much more challenging and require tools that are much more sophisticated than
the flashlight, screwdriver, pressure gage and multi-meter that would have been used to check-out, troubleshoot, and repair the older control panel.

So, if you are still with me, you may be wondering what my point is in showing and discussing these pictures on my blog. I guess there are several points when I think about it.

One is to simply preserve a piece of the history of our industry and give some of the younger players a feel for where we came from and some perspective on how much things can change over the course of your career.

The other is to point out that even though the methodology we use to achieve our intended results with HVAC systems – in general terms, safe comfortable controlled environments – tends to evolve as technology evolves, the physics behind the systems are generally
the same as they always were.

So bottom line; I guess I am encouraging you to embrace the new technologies that are coming at us every day and use them to their best advantage to make your buildings and systems more efficient and sustainable. But in doing that, don’t loose sight of the
fundamentals behind them. Embracing one with out the other ignores the history of our industry and everything we have learned and will be a step in the wrong direction as we face the challenge to make our buildings more efficient and sustainable.

David Sellers
Senior Engineer – Facility Dynamics Engineering

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