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Commissioning: Testing Frustrations

Face time and prep time might have kept this test on course.

I had a frustrating functional performance testing experience recently. Although frustration can be a common theme during testing, this particular episode had a single consistent issue that got me thinking.

We were testing very simple HVAC systems controlled via a DDC system. Just about every sequence of operation failed to perform as specified. When we encountered problems, the desired sequence was explained to the controls technician, he said he could reprogram it on the spot, and I allowed him a few minutes to do so. This was repeated a number of times during the testing session.

While working on the reprogramming, the controls technician explained what he was doing and assured me that it would work. I did a cursory check of the revised programming, but the planned sequence of testing was interrupted and I lost confidence that we were fully testing the intended operation. Because we were under time pressure to complete our work, I allowed the testing to move forward to the next system, where we then encountered our next problem and repeated the reprogramming and improvised retesting process.

I walked away from that session with a plan to go on-line and test each of the control strategies again on my own. The DDC system allowed me to do that remotely from my office. If the systems didn’t perform as expected during my organized and unpressurized retesting, I would need to call the controls contractor back to the building to go through the systems again.

This is obviously not how the testing should have gone. The intention of functional performance testing is for the contractor to demonstrate proper performance of the systems, not for the commissioning professional and contractor to discuss and troubleshoot the controls programming.

In thinking through the root cause of my frustration, I realized that I took the “simple systems” too casually. I did not follow my own recommendations with respect to preparation for successful testing. I think that was because the commissioning effort for these systems seemed relatively minor, and proper preparation might have doubled the time required. So, what did I neglect? I believe the following two key elements would have made a big difference.

Controls Integration Meeting

Instead of relying solely on the written word for communicating the intended control sequences, a face-to-face meeting is always surprisingly helpful for clarifying intentions. In every case, at least one thing that one person believed was clear and unambiguous was interpreted differently by another team member. Being face-to-face, with the opportunity to draw pictures and verbalize expectations and understandings, is invaluable.

I recommend convening all of the people involved in achieving a functional system, including contractors responsible for systems with which the commissioned systems need to communicate (fire alarm, security, lighting controls, etc.). This meeting should not only be used to confirm that everyone is on the same page with respect to how the systems are to operate, but it should also be used to clarify who is responsible for wiring and programming each element of the system. This latter objective will help reduce the chances of duplicated efforts and/or missed responsibilities.

Functional Test Procedure Review

For best results, the contractors responsible for each system should be given the test procedures and acceptance criteria well in advance of the scheduled testing. Functional performance testing is not only an open-book test, it is an open-book test with all of the answers filled in.

At the very least, contractors should be required to review and comment on the test procedures prior to the procedures being finalized by the commissioning professional. The contractors will often have meaningful recommendations with respect to increasing the efficiency of (and mitigating the risk associated with) each test.

Ideally, of course, the contractors would run through the test procedures on their own prior to announcing the systems are complete and ready for official functional testing. I believe this has happened on fewer than five of my past projects, not necessarily from a lack of interest on the contractors’ part but from an absence of the planning, scheduling, and coordination required to have all of the systems complete and ready for testing in time to perform a pre-test. I hold out hope, however, that someday pre-testing will be the norm instead of the exception.

In summary, both of these commissioning process strategies are useful for avoiding misunderstandings, wasted time, and frustration during functional performance testing. As is often the case, more time spent on early planning and communication will often result in less effort in the end.

 

Commissioning: Getting It Right

Engineered Systems, September, 2009

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