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The Future of BAS Design
I want to thank Paul Ehrlich for his years of dedication to this column and am excited to be able to provide readers with my Building Automation thoughts, insights, etc. on a monthly basis.
Ira Goldschmidt, P.E., LEED®AP
January Issue - BAS Column
Last month Paul provided a vision of the future of BAS for the next decade. I’d like to begin my series of columns with a vision of the challenges that I believe the industry will face in meeting this “future.” First, let’s address;
CONTROLS SYSTEM DESIGN
I too am delighted
to see some emerging efforts that show great promise in providing
better design tools to engineers and other BAS specifiers. The
question is will these efforts be “too little, too late”?
If we look back on the pre-DDC days of 1980-ish and earlier the fact is that control systems were relatively simple; i.e., there was only so much you could do with pneumatic and electric controls before they would fail under the weight of excessive complexity. HVAC designs were also much simpler since none of the myriads of energy conservation-driven codes, standards, and incentive programs, along with the associated technical advances, were yet in place.
In fact, HVAC system choices and variations in the pre-DDC days were so limited such that it was possible to develop a very reasonable and repeatable set of standard sequences of operation. Better still these “standards” were well-understood and documented (along with the controls designs required) by the major controls manufacturers. This meant that controls “design” was a fairly straightforward effort. It could even involve substantial assistance by a local TC contractor without fear that this would give that contractor an unfair bid-day advantage (due to the equivalency of most pneumatic/electric controls).
Today we enjoy none of the above benefits from the “good old days.” Don’t get me wrong: I don’t long for those days just because the design efforts were substantially less. Just the opposite: the great variety of today’s HVAC design choices (and code/standard constraints) have allowed (forced?) us to innovate how BAS's are applied to our projects greatly. However, against this backdrop of innovation is the sad reality that design fees have fallen. Is it any wonder that the effort put towards today’s controls designs cannot even rise to the level afforded during the “good old days” (maybe they were really better)?
So all of this puts a lot of pressure on initiatives to provide much better BAS design guidance/assistance. Fortunately a closer look at the not-yet-official ASHRAE Guideline 36P “High-Performance Sequences of Operation for HVAC Systems” indicates that it might be just what is needed.
The stated purpose of Guideline 36P (from “Part 1 – Purpose”) is “…to provide uniform sequences of operation…”.
Note the word “uniform,” which indicates that this is not intending to
be merely a guideline but a reference manual of standardized
sequences. Further, “2.1 Sequences of Operation” additionally
says “Lists of hard-wired points and control diagrams are included.”. Wow: this is beginning to sound like the good-old-days!
Further inspection of Guideline 36P document reveals how seriously it is attempting to fulfill the stated purpose. First off, the first 20+ pages of “Part 5 – Sequences of Operation” covers detailed definitions of the various elements that go into the sequences. These include such things as a “control loop,” how “trim and respond” is to be used for resetting setpoints (e.g., duct static based on VAV box demand), how to stage and rotate equipment (e.g., multiple chillers), and much/much more. Finally, the specific sequences provided are way more prescriptively-detailed than anything even the most sleep-deprived engineer could ever justify developing for most projects.
If successful, the sequences and point database described in Guideline 36P could be programmed into BAS controller firmware. In other words, these would be “canned” sequences in the same manner as many of today’s VAV box controllers. This would allow more complex equipment/systems (e.g., VAV AHU’s, central plants) to benefit from a far simpler installation, setup, and testing process (not to mention the on-going maintenance).
For those who haven’t looked at this document – please do: it is readily available at http://gpc36.savemyenergy.com/public-files/. It will be very interesting to see whether it can evolve into a tool that is embraced as a “standard” by the industry so that controls design can once again be as simple as it was in the “good old days.”
About the Author
Ira has worked in
the building industry for over 35yrs. as a controls tech, MEP designer,
and consultant providing design/guidance for critical-facility BAS’s
& Intelligent Building systems' integration. He is a
co-author of the ASHRAE BACnet® Standard and Guideline 13 “Specifying
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