Engineered Systems NEWSHVAC Design/Construction ProcessHigh-Performance Buildings & Automation

The Importance Of Doing BAS Right

By Paul Ehrlich P.E., Ira Goldschmidt P.E.

Many elements of an MEP design are relatively straightforward. There is usually a right way to do things and a wrong way. Often, these decisions are clearly based on codes, or at very least on convention. Controls and BAS, however, are rarely this straightforward, and in many cases there is a good, better, and best way to control a system. Understanding these options, the costs and benefits, and how to achieve them on your next project is not well understood by owners and their design teams.

So what are the differences between these options? The simple answer is as follows.

Good:A good system is one that simply works. This means that it is able to satisfy the owner’s requirements for basic safety and temperature control. Think of “good” control as what is equivalent to what we could do with pneumatic or electronic controls. For example, on a VAV air handler, the basic functions would include the ability to control static pressure and discharge temperature control.

Better:A better control system starts to add in efficiency on top of the basic control of the “good” system. For the air handler example, we would add basic economizer control, make sure that the unit is properly scheduled, and ensure that the associated VAV boxes have proper flow setpoints for heating and cooling modes.

Best:So what is best? The best system uses controls to dynamically optimize efficiency. On an air handler, this means more sophisticated economizer control, dynamic reset of static pressure discharge setpoints based on feedback from the VAV zones, and integration to the fans’ VFDs. Best systems will often have more monitoring and integration, allowing the operator to get additional information for decisionmaking and ongoing improvement.

SOMEWHERE IN THE MIDDLE

So what ends up on most projects? We find that it is something between good and better. Why? The answer isn’t as simple as it seems. Here are a few reasons we get less then best.

Design:On many projects, controls design does not get adequate attention. Some of this may be related to budget, but often it is the result of poorly developed specification, sequences, and points lists. Project designers need better training and focus on systems, optimization, and controls design.

Development:Even a system that has been designed to be “best” can easily degrade during installation. Project schedules make it imperative that systems get started and work properly (e.g., good). To take it to the next level takes added focus on the part of the contractor and the project team. One way to ensure that this happens is to utilize a third party to validate and commission controls. The commissioning agent works closely with the controls contractor to make sure that systems have been properly programmed and optimized. They often will also assist the operator with understanding the system and understanding how to operate it in an optimal manner.

Why would we want to go from good to best? After all, it doesn’t come for free? An optimized system has the potential to provide improved operation, reliability, and of course energy efficiency. As an industry we need to be striving for greatness.ES

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Paul Ehrlich is the founder and president of Building Intelligence Group LLC, a consulting firm focused on the delivery of energy efficient commercial buildings with a focus on controls, systems integration, and building to grid integration. For more information, see www.buildingintelligencegroup.com.

Ira has worked in the building industry for over 35 years as a controls tech, MEP designer, and consultant providing design/guidance for critical-facility BAS and intelligent building systems integration. He is a co-author of the ASHRAE BACnet® standard and Guideline 13 — Specifying DDC Controls.

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