Understanding Airside TAB Measurements | P2S

Kent Peterson

Vice President

PE, ASHRAE Presidential Fellow, LEED AP BD+C, BEAP, MCIBSE

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Testing, adjusting, and balancing (TAB) is a critical component of building HVAC system installation, maintenance and operations. The testing, adjusting, and balancing report is a report card for the system’s performance. As engineers, we are required to specify what is required for measurement, testing, adjusting, and balancing and to design HVAC systems that can be measured. We are also required to review and understand the results of the testing and measurement data. In the author’s experience, many designers rarely look beyond the measured-to-specified values in the TAB report.

An understanding of TAB measurements allows designers to look deeper into system performance to better understand if the system is operating as designed. This month, I provide guidance to assist engineers and designers to design for measurement and balancing of airside systems, along with tips on how to evaluate airside TAB measurements.

Air Measurements

Primary measurements to verify fan system performance include airflow and pressure. Total pressure, Pt , is the sum of static pressure, Ps , and velocity pressure, Pv , at a specific plane. Static pressure is the portion of the air pressure that exists by the degree of compression only. Velocity pressure is the portion of air pressure that exists by virtue of the rate of motion only.

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