The purpose of Testing, Adjusting and Balancing (TAB) is to assure that an HVAC system is providing maximum occupant comfort at the lowest energy cost possible.
Most of today's HVAC systems are being designed with many more individually controlled temperature zones in order to improve occupant comfort. Variable speed fans and pumps are becoming more commonplace to provide the exact amount of heating and cooling system capacity in a manner that minimizes overall energy usage. New occupant air ventilation codes are much more restrictive and at the same time building envelopes are becoming much tighter. The combination of constantly changing HVAC airflow rates and increased demand for fresh- and filtered-ventilation air for all occupants is placing more emphasis on fine tuning HVAC system operation.
Testing, adjusting and balancing of all HVAC systems in a new facility is needed to complete the installation and to make the system perform as the designer intended. Assuming that the system design and installation meet the comfort needs of the building occupants, testing, adjusting, and balancing of the HVAC system fine tunes occupant comfort levels while keeping energy use to the lowest level possible. This is extremely important in this era of rising energy costs.
It is important to make sure that all factory equipment startup service has been completed before beginning any TAB work. Most specifications on new building construction usually require a factory representative to be present during the initial startup and adjustment of the mechanical equipment central boilers, chillers, large variable-speed motor drives and cooling towers. This initial equipment checkout is also usually required to activate the factory warranties and is not part of the TAB contractor's responsibility. After this initial startup service has been completed, the TAB contractor should be informed that the systems are operating properly, that all safety interlocks and protective devices are functioning, and the systems are ready to be balanced.
The TAB phase of any building construction or renovation is intended to verify that all HVAC water, air-flows and pressures meet the design intent and equipment manufacturer's operating requirements. It is rare to find an HVAC system of any size that will perform completely satisfactorily without the benefit of final adjustments. This is why it is considered a "best practice" for the designer to specify that TAB work be part of the overall HVAC system installation