Engineered Systems - December 2008 - (Page 18)

Commissioning BY REBECCA ELLIS, P.E. COMMISSIONING Is Just The Start And when it comes to system optimization, occupancy only marks the end of the beginning. A professional colleague of mine recently shared his firm’s experience with commissioning their new office building expansion. It was a LEED® Silver certified project and they were very focused on energy conservation. The commissioning team conducted functional performance tests at the end of construction and verified that all of the HVAC systems performed as intended. After occupying the new building, the firm found that they were using more energy than expected. This led them to re-examine how the systems were controlled, how the building was being used, what the true occupancy patterns were, etc. They tweaked and measured and then tweaked and measured again, until they honed in on the optimal performance and minimal energy consumption practical for their systems and business operation. Although they are still trying to reduce energy consumption to meet their original energy budget goals for the building, they are significantly closer to that goal than they were on the day they finished commissioning it at the end of construction. A MULTI-STAGE PROCESS This is a story of commissioning success and not, as might be considered at first blush, a story of commissioning failure. Verifying that systems perform as designed and intended by the owner’s project requirements at the end of construction is a critical first step in the life of new building systems. If we use human development as an analogy, design and construction commissioning is similar to prenatal care, a safe labor, and delivery of a healthy baby. However, there is a tremendous amount of attention and effort that is required of the parents to help that baby develop into a child and eventually into an adult who goes on to fulfill his potential. Being both a parent and a commissioning professional, I will admit this analogy can be taken only so far. For example, proportionately more effort goes into the post-birth stage for people than goes into the post-construction stage for building systems. The concept is similar, though, and it is something that I believe most building owners and operators do not realize, appreciate, and/or embrace as fully as they might. If a building owner receives a successfully commissioned system, accurate and complete O&M documentation, and systems training at the end of construction, that is something to celebrate. The building operators are then prepared to take responsibility for the systems and take them to the next level of performance. No matter how excellent a project’s integrated design team (architects and engineers working together) is, no one can predict exactly how the unique building structure and mechanical, electrical, and plumbing systems will perform following construction and after real people move in. There are too many elements and people involved in constructing a building to be able to control the outcome to perfection. As such, structures may be leakier (hopefully just air and not water); ductwork may have more transitions and turns; thermostats may need to be placed in non-ideal locations; Functional performance testing Functional performance testing should b successfully completed h ld be f ll pl t d before the owner moves in and before the owner moves in and begins using the facility. By begins using the facility. By definiti , th efore, commissioning fi ition, ther f , i i ig is performed under conditions that performed under conditions that the building will never see again. the building will never see again. What good is that? t d th t? owner equipment may have different electric and heat load characteristics than anticipated, etc. Construction-phase commissioning is about verifying that the systems will perform as intended under the originally anticipated conditions. This is because functional performance testing should be successfully completed before the owner moves in and begins using the facility. By definition, therefore, commissioning is performed under conditions that the building will never see again. What good is that? IMPROVING THE PERFORMANCE BASELINE The “good” is the establishment of a performance baseline that should only be improved upon as the building is occupied and put into regular operation. Although a few building operators understand this and plan to fine-tune the systems as use of the facility matures and changes over time, many building owners want to believe that commissioning has delivered optimized systems that should remain unchanged. The end-of-construction performance baseline should not be seen as the target for future measurement and verification efforts but should be seen as the minimum performance standard against which future enhancements and fine tuning can be measured. In summary, the design and construction commissioning process is only the first step in an ongoing process that continually looks at ways to match system integration, setpoints, schedules, and control sequences to the dynamic needs of building occupants and processes. This is a new way to look at systems operation. Perhaps the group responsible for building systems should be renamed; instead of “Operations and Maintenance,” what about “Optimization and Maintenance”? ES Ellis is president of Questions & Solutions Engineering, Inc. (Chaska, MN). E-mail her at rteesmag@qseng.com. 18 En gi neer ed S y stem s December 2008

Table of Contents Feed for the Digital Edition of Engineered Systems - December 2008

Engineered Systems - December 2008 Contents Editor's Note HVAC Challenge Back2Basics Case In Point Commissioning Building Automation HVACR Designer Tips Applications Checklist Lakefront Library: Radiant Systems Meet Natural Ventilation Before (And After) The Flood Basics For Refrigerant Chillers Wire-To-Shaft Efficiency For HVAC Pumps Products Glossary Classifieds Advertiser Index Tomorrow’s Environment

Engineered Systems - December 2008

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