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Balancing And Commissioning

How does commissioning relate to testing, adjusting, and balancing (TAB)? Is TAB the same as commissioning? Is TAB part of the commissioning process? Is commissioning a duplication of the TAB effort?

As with much of the commissioning industry, there are no hard and fast, universally accepted answers to these questions. Different facility owners have unique expectations and different commissioning providers offer a variety of services. The important issue for each individual design and construction project is to tackle these questions and define roles and responsibilities clearly, coordinate schedules, and make sure that unwanted duplication of effort and unanticipated gaps do not occur.

TAB is an integral part of the process of making systems work and documenting that they perform according to the design intent and contract document requirements. In that regard, the TAB contractor straddles the world of quality control and the world of commissioning. (Refer to Getting it Right column from March, 2002 for a discussion of the difference between quality control and commissioning.) TAB processes and procedures are well defined and are a typical expectation for every construction project. As such, they are ahead of the game compared to commissioning.

We have found, however, that some facility owners question the rigor and validity of their TAB contractors’ efforts at the end of construction projects. For a number of reasons, including compressed schedule, poor resource planning, subcontractor terms and conditions, and/or lack of emphasis on TAB, some building owners are asking that the TAB process be improved, overseen, verified, and/or included in the commissioning provider’s scope of services.

This column is not intended to be a dissertation on the TAB industry but simply a presentation of the fact that TAB and commissioning need to be coordinated.

In general, we have seen three types of approaches to the TAB/commissioning interface; all dictated by each particular facility owner’s preferences, past experiences, and budget.

Option #1: Successful TAB process and documentation is a prerequisite to initiating commissioning functional performance testing. Commissioning provider reviews TAB report prior to moving into functional testing.

Option #2: Successful TAB process and documentation is a prerequisite to initiating commissioning functional performance testing. Commissioning provider reviews TAB report and witnesses a random sample of the TAB contractor’s measurements in the field.

Option #3: TAB process is incorporated into the commissioning provider’s scope of services.

Option #1 is for the owner who is comfortable with the TAB process as typically provided on a project. The intent of having the commissioning provider review the TAB report is to confirm that all aspects of the TAB work are complete and functioning as designed. In addition, the commissioning provider can learn and benefit from any notes the TAB contractor is able to provide with respect to system operation. No field spot checking of the TAB contractor’s work is required, but functional performance testing could (but won’t always) uncover balancing problems and serves as a pseudo-spot check.

Option #2 is for the owner who is skeptical of the TAB results and would like to have a third party (commissioning provider) not only review the written report but also witness some of the TAB procedures. This process tends to increase the level of confidence with respect to the TAB report data but is clearly more costly for the owner. Option #2 typically involves the commissioning provider reviewing the TAB report and then meeting the TAB contractor at the site to re-measure randomly selected data points from the report. This means more commissioning provider time and fee and, since this expectation needs to be clearly defined in the specification, more TAB contractor time and fee. An alternate approach that might be considered is for the commissioning provider to do their own measurements of the TAB data without the TAB contractor present. However, this will almost always result in a discussion of equipment calibration, proper procedures, data interpretation, etc., if non-compliant data is read by the commissioning provider. Therefore, if field spot checking is to occur, I strongly recommend that it be the commissioning provider witnessing the original TAB contractor performing the re-measurements.

Option #3 is a rare, but not unheard of, approach which defines commissioning such that all of the TAB work is under the commissioning provider’s umbrella. This is similar to and subject to the same issues as having the TAB contractor report directly to the owner instead of to the mechanical or general contractor. The October, 2002 Getting it Right column will be dedicated to the intricacies and coordination associated with Option #3.



Engineered Systems, September, 2002

Rebecca Ellis, PE, LEED AP, CCP, CxA
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318