Bring TAB specs in line

For the best test and balance results, perform a specification checkup on each project.

06/13/2008


Better test and balance (TAB) results are just a specification away. All too often, TAB specifications are not consistent with project specifics and modern TAB procedures. These disconnects can lead to confusion and frustration for both the design professional and the TAB firm.

When TAB supervisors prepare a price for a balancing project, they review the mechanical drawings, equipment submittals, and the TAB specification. What TAB supervisors often find are TAB specifications that:
* Are not project-specific
* Request non-TAB work or services
* Include irrelevant testing requirements.

Project specific
Producing project-specific TAB specifications helps the TAB firm identify the true scope of the work. Often specifications detail requirements for equipment or systems not included in the project. For example, specifications might list hydronic data where no pumps exist. Also, ambiguous scope of work statements such as “calibrate controls,” “participate in commissioning,” or “perform opposite season testing” can result in inconsistent TAB pricing. Fear of the unknown will cause TAB firms to increase their estimate.

Most of today’s model specifications are editable. Using this capability to match the TAB specification with the project characteristics will significantly improve the final TAB product and promote competitive pricing.

Download a PDF example of TAB specifications .

TAB services
TAB specifications work best when they cover the work that most TAB contractors routinely perform. Some TAB specifications assign tasks to the TAB provider that are best performed by other members of the construction team. Tasks might include calling for the TAB contractor to provide equipment start-up, motor or sheave replacement, or record refrigeration pressures.

Most TAB contractors do not have the proper licensing or equipment to access HVAC refrigeration systems. Assigning these items to mechanical service technicians is more appropriate. Also, avoid giving the TAB firm sole responsibility for control calibration. A better approach is to have it coordinated, and describe the calibration requirements in the control and TAB specifications.

Download a PDF example of a pre-TAB checklist .

Irrelevant testing
One common specification requires measuring wet and dry bulb every two hours for two consecutive eight-hour days, in every occupied zone. This requirement is of little value because it provides data that are only slightly useful. The same specification, in its unedited state, also requires IAQ measurements that should be provided by an industrial hygienist.

It is a given that all design professionals want their designs to work correctly. Savvy designers know a TAB report provides tangible evidence that systems are performing as intended. Rather than load the TAB specification with unrealistic tasks, designers should consider specifying systems commissioning for a project. Commissioning promotes HVAC systems that are designed, installed, started, and balanced correctly.

Out-of-date or unrealistic TAB specifications cause confusion, frustration, and erratic TAB pricing. Avoiding the disconnects outlined in this article will yield better results. Moreover, if it is time to update your TAB specification, consider having a qualified commissioning supervisor include this service in the next project.

For additional TAB specifications, visit the National Environmental Balancing Bureau or ASHRAE Web site.





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