Commissioning: BCXA Essential Attributes, Part 5
This month I am going to dedicate my column to a single essential attribute of commissioning: the one that addresses functional performance testing (FPT). This is the ninth of eleven Essential Attributes of Building Commissioning defined by the Building Commissioning Association (BCxA).
ATTRIBUTE #9The functional testing program objectively verifies that the building systems perform interactively in accordance with the Project Documents. Written, repeatable test procedures, prepared specifically for each project, are used to functionally test components and systems in all modes of operating conditions specified for testing. These tests are documented to clearly describe the individual systematic test procedures, the expected systems response or acceptance criteria for each procedure, the actual response or findings, and any pertinent discussion.
SYSTEMSFunctional test procedures are about testing “systems,” not equipment. By the time the project reaches the functional testing phase, the individual pieces of equipment should already have been confirmed to be acceptable and operating properly. Depending on the equipment, this can involve standard quality control checks of equipment against shop drawing submittals, installation verification against manufacturer’s recommendations, energization and startup procedures, and equipment operational check-out.
INTERACTIVEIt is not good enough to just functionally test individual systems, such as the heating hot water system, air-handling system, fire alarm system, lighting control systems, etc. It is also critical to methodically test all intersystem communication and operation. This testing of system interoperability can be performed with separate systems integration test procedures, or it can be integrated into the functional test procedures for the individual systems which play a part in a larger integrated whole. This was the topic of my July, 2005 column.
REPEATABLE“Repeatable” is one of those concepts we all learned in high school science. An experiment (test) is not valid unless it is documented to the level where someone else could repeat the process and arrive at the same result. In the case of commissioning, I believe the intent is for anyone knowledgeable in building systems operation - whether from an engineering, construction, and/or operations background - should be able to perform the test and obtain the same results. This is particularly pertinent for future systems recommissioning by building operators.
CLEARLY DESCRIBEDThe key to repeatability is in the level of detail provided in the test procedures. The written procedure should unambiguously explain what needs to be done in the attempt to simulate and demonstrate proper performance of a specific operating condition. For example, simply stating, “Test the economizer mode,” is not a repeatable process. Instead, there need to be very clear step-by-step, device-by-device instructions on (1) how to put the system into economizer mode; (2) how to simulate a call for increased cooling in economizer mode; (3) how to simulate a call for decreased cooling in economizer mode; and (4) how to make the system switch from economizer operation to minimum outside air operation. Directions to be included in the each step of a test procedure should include what setpoints and/or inputs to override and to what values.
EXPECTED SYSTEMS RESPONSEThe requirement for repeatability extends into the results assessment part of functional testing. For each set of conditions defined in the written test procedure, there should be an equally detailed written description of the acceptance criteria. In order to avoid time-consuming disagreements regarding whether a step has passed or failed, these criteria must be presented objectively in such a way that everyone present can agree on what they are observing. For example, the following are not objective acceptance criteria: (1) the system performs per specification requirements; (2) the system performance meets code requirements; and (3) the system responds per LEED® requirements.
As with the procedure itself, the acceptance criteria need to be defined for each impacted sensor or device. If a temperature needs to increase, note the starting and ending temperatures and confirm that the latter is higher than the former. If a valve needs to open, confirm that the valve control signal changes and visually confirm the valve physically opens. If a damper needs to close, confirm that the damper control signal changes, the damper actuator physically moves, and observe that the damper blades close. These are all things upon which reasonable people observing the same thing can agree.