Overview
Testing, adjusting, and balancing (TAB) are the three critical steps in ensuring the proper operation of heating, ventilation, and air conditioning (HVAC) systems. These processes are commonly associated with commercial building construction, involving specialized contractors who have dedicated personnel for performing TAB services.
Generally, the TAB specialist conducts air and hydronic measurements on HVAC systems, adjusting the flows as necessary to achieve optimal performance of the building’s environmental equipment. This balancing is typically based on the design flow values specified by the Mechanical Engineer for the project. The TAB contractor then submits a written report summarizing the testing and balancing results, highlighting any deficiencies discovered during the process. Often, facility managers will engage a TAB contractor to help identify pre-existing or common issues within a facility.
Testing
Testing involves using specialized and calibrated instruments to measure temperatures, pressures, rotational speeds, electrical characteristics, velocities, and air and water quantities. This process evaluates the performance of equipment and systems.
Adjusting
Adjusting involves the final setting of balancing devices like dampers and valves, adjusting fan speeds and pump impeller sizes, as well as fine-tuning automatic control devices such as thermostats and pressure controllers. This process aims to achieve maximum specified system performance and efficiency during normal operation.
Balancing
Balancing is the systematic regulation of system fluid flows (air or water) using standardized procedures to achieve the specified design airflow or water flow. To begin balancing a system, identify the terminal with the lowest flow according to the engineer's drawings. Once the "low" terminal is located, adjust all other diffusers/grilles (air) or circuit balancing valves (water) to proportionally match this original "low" terminal. For optimum efficiency, at least one terminal must remain fully open.