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Commissioning: Systems Verification Testing

Verification testing of systems being commissioned can begin when the systems are fully operational, balanced, and fine tuned.. Verification testing should occur at the point where the systems would be turned over to the owner in a non-commissioned project. The commissioning verification testing process is inserted into the project to confirm that the systems perform as designed instead of leaving it up to the owner’s operations and maintenance staff to discover any problems which may exist. Finding problems early while the contractors are still on-site and readily available to correct them saves time and effort for everyone.

An HVAC system is ready for verification testing when the following prerequisites are met:

  • All electrical power hookups are complete.

  • All steam, chilled water, and other “utility” hookups are complete.

  • All temperature, humidity, pressure, air flow, and other sensors are installed, verified to be properly wired, and calibrated.

  • All system setpoints, i.e., minimum outside air damper positions, supply duct static pressures, hydronic system differential pressures, etc., are determined by and coordinated with the balancer.

  • All air and water balancing is complete.

Once these prerequisites are satisfied, the commissioning agent can begin conducting the verification tests. These step-by-step tests were defined during the design phase of the project, incorporated into the commissioning specification, and fine tuned following shop drawing review and approval. Each step is a pass/fail confirmation of one element of the specified control sequence for the systems being commissioned. Test procedures can vary from 3-5 steps for very simple systems (unit heaters, for example) to more than 100 steps for complex systems (air handling units with multiple modes of operation, i.e., normal, unoccupied, warm-up, smoke evacuation, etc.). Examples of simple test procedures are included each month in Engineered Systems’ Back-to-Basics feature.

Although, in most cases, the verification tests are created, planned, directed, and documented by the commissioning agent, participation by the contractors whose systems are being commissioned is mandatory and participation by the owner’s operations staff is recommended. The contractors need to be involved in the testing process in order to answer questions and, perhaps, to correct “easy” problems immediately. They also need to be involved from a liability standpoint, because these systems are typically not turned over to the owner yet and manipulation by anyone but the contractors could lead to warranty complications.

Participating in the hands-on verification tests is an invaluable tool for training the owner’s operations staff. It does not replace more traditional training sessions but enhances it in such a way that the operators can actually see the systems in action instead of just hearing about them.

Problems will invariably be found during the course of the verification tests, i.e., at least one of the steps will “fail” to meet the operational requirements. It is important for the people involved to understand the difference between “testing” and “troubleshooting.” The tendency of everyone will be to stop and correct the problem. In the interest of maintaining momentum during the testing process and being respectful of everyone’s time, however, it is important to limit the amount of troubleshooting undertaken during the test. We have found it useful to define a deficiency as any anomaly which can not be corrected in less than 5 minutes. If a problem is not corrected within 5 minutes, the deficiency will be documented for future attention, and the testing team will move on to the next step of the test procedure.

Each deficiency needs to be written up on a separate corrective action form (CAR). Because the commissioning agent typically has no contractual authority over the contractors, the commissioning agent can not direct the contractors on how to fix the problem but should simply identify what the problem is. The commissioning agent may have a good idea of what the cause of the problem is and how it might be corrected and should share this information on the CAR, but the suggestion can’t be construed as “directing” the contractors.

It is the contractors’ responsibility to correct the deficiency. If it is unclear what the solution is or if more information is required from the design engineers, the contractor can generate a Request for Information (RFI) in order to involve the designers in the corrective action. If it is deemed impractical or unnecessary to correct a deficiency identified during verification testing, the design engineers can formally document a change in design criteria and accept the performance of the system as installed, programmed, and demonstrated. This documentation will become a permanent part of the project records along with a description of how, if at all, the change in performance criteria impacts the Design Intent Document.

Once the contractor confirms that all deficiencies have been addressed, the commissioning agent will direct retesting activities. Retesting is a repeat of the original verification test procedures to the extent deemed necessary by the commissioning agent to “prove” that each deficiency has been corrected satisfactorily.

 

Commissioning: Getting It Right

Engineered Systems, May, 1998

by
Rebecca Ellis, PE, LEED AP, CCP, CxA
President
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318
rteesmag@QSEng.com