8. Conclusion

The ultimate goal of the commissioning process is the reliably integrated control and operation of a building and its systems. An orderly, methodical process that is integral with the design and construction of the project from the start and embraced by all parties can address the complex interactions that occur simultaneously among the building, its systems, the occupants and the environment.

But, time takes its toll; moving parts wear, heat transfer surfaces foul, and the requirements of the loads change. For the benefits from the project’s commissioning process to persist, it is essential that the operating team pick up the ball and run with it. Commissioning providers can have a large role to play in this via the manner in which they handle the project and document the results. Examples include:

·       Including the operating team in the process to the extent they were willing to participate.

·       Answering the operating team’s questions and listening to their concerns, which are usually quite legitimate.

·       Include training on utility bill analysis, benchmarking, and trend analysis in the overall training syllabus provided for the operators.

·       Documenting the results of the effort in a commissioning report and system manual, including copies of the test procedures that were used, recommendation for retesting and operating under unusual conditions, a description of the systems and the reasoning behind them, and a narrative description of how things are supposed to work.

Recent research had shown that all of these items were crucial to the persistence of the benefits of commissioning. All of these steps are part of the integration process, and they integrate the operating team with the building

[1]   For more on integrated design, see “Improving Mechanical System Energy Efficiency through Architect and Engineer Coordination,” a free download from www.energydesignresources.com. Or try your hand at an interactive integrated-design tutorial also available from the Energy Design Resources web site.

[2]   For an example of how to calculate the savings potential associated with this suggestion, see Appendix C – Calculations of the Functional Testing Guide.

[3]   While perfectly linear dampers are possible in theory, achieving the result in the field under all operating conditions is a practical impossibility. Devoting attention to damper sizing during design can yield near linear characteristics which will usually be good enough for most systems. If dampers are oversized (a common problem currently), the result will be damper characteristics that are highly non-linear, approaching a two-position performance. As will be seen from this discussion, this can have a significant impact on a system’s ability to achieve stable operation. A detailed discussion of damper sizing can be found in Chapter 3 – Economizer and Mixed Air, Section

[4]   The change in return fan discharge static and subsequent speed change by the return fan would also impact other control processes in a manner similar to what was described in the preceding section.

[5]   See Figure 3.16: Piston actuator linkage arrangements and Chapter 3- Economizer Components Supplemental Information for a more detailed discussion of this topic.

[6]   Note that even though the return fan brake horsepower requirement is 2.32 bhp, the motor provided is 5 bhp rather than 3 bhp (the next incremental size over the brake horsepower requirement). This is because a 3-hp motor does not have enough torque to start the large fan wheel. A similar effect to the problem described here could manifest itself if the existing motor were replaced with a motor that had a different starting-torque characteristic. Different motors have different starting-torque capabilities that are a function the motor construction characteristics. Thus a motor from manufacture A may have more torque than a motor of the same size from manufacturer B. Most fan manufacturers list the fan wheel’s moment of inertia (commonly termed WR2) in their literature. This parameter should be compared to the WR2 capability of the any replacement motor prior to purchase to avoid start-up problems.

[7]   See Strategies for Improving Persistence of Commissioning Benefits for more information on how training and other strategies impact persistence. This document can be downloaded at www.cacx.org.

[8]   A general discussion of testing hierarchy in the context of an air handling system can be found in the Actuators in Chapter 3 Economizer Components Supplemental Information.

[14]             For more information on control loops and loop tuning see An Overview of Proportional plus Integral plus Derivative Control and Suggestions for Its Successful Application and Implementation from the proceedings of the ICEBO 2001 conference, which is available from the California Commissioning Collaborative online commissioning library at www.cacx.org.

[15]             This paper and many of the references it contains can be downloaded from www.cacx.org.

[16]             For a detailed discussion of this topic, refer to the Energy Design Resources design brief titled Design Review which can be downloaded at no cost from www.EnergyDesignResources.com.

[17]             For additional information on fan heat see Fan Heat, its Source and Significance by Gerald Williams, published in the 1989 issue of Heating, Piping, and Air Conditioning.