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The Importance of Doing BAS Right
An optimized system has the potential to provide improved operation, reliability, and of course energy efficiency.
Paul Ehrlich, Ira
& Angela Lewis
Most 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, is rarely this straight
forward, 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 achieve satisfies 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 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 units variable frequency drives. Best systems will often have more monitoring and integration allowing the operator to get additional information for decision-making and ongoing improvement.
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 than 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.
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 (i.e. good). To take it to the next level takes added focus on the part of the contractor and the project team. One way to assure 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.
About the Authors
Paul and Ira first worked together on a series of ASHRAE projects including the BACnet committee and Guideline 13 – Specifying DDC Controls. The formation of Building Intelligence Group provided them the ability to work together professionally providing assistance to owners with the planning, design and development of Intelligent Building Systems. Building Intelligence Group provides services for clients worldwide including leading Universities, Corporations, and Developers. More information can be found at www.buildingintelligencegroup.com We also invite you to contact us directly at Paul@buildingintelligencegroup.com or firstname.lastname@example.org
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