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. The important issue for each individual design and construction project is to tackle these questions and define roles and responsibilities clearly, coordinate schedules, and avoid unwanted duplication of effort or unanticipated gaps.

QC and Commissioning

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," March 2002, for a discussion of the difference between quality control and commissioning.) TAB processes and procedures are well defined and, 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.

Three Types

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.

  • 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.
  • 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.
  • TAB process is incorporated into the commissioning provider's scope of services.

Option 1 is for the owner who is comfortable with the typical TAB process. 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 from any notes the TAB contractor provides about 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 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 remeasure randomly selected data points from the report. This means more fees for providers and more of the commissioning TAB contractor's time.

An alternate approach that might be considered is for the commissioning provider to do his 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 noncompliant 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, asserting that all 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. Next month's column will be dedicated to the intricacies and coordination associated with Option 3. ES