NEBB Testing, Adjusting and Balancing Certified Professional (CP) key terms

The systematic process of measuring HVAC system performance, adjusting components to design values, and documenting final airflow, pressure, and temperature conditions so the installed system delivers intended performance.

The final phase of TAB work in which dampers, valves, sheaves, and controls are set so each terminal and circuit receives its proportionate or design flow within allowed tolerance.

The airflow rate, usually in liters per second or cubic feet per minute, that the engineer specifies for a terminal, zone, or equipment item on the contract documents.

The permitted deviation between measured and design values, commonly expressed as a percentage of design flow, within which a system is considered acceptably balanced.

A method that adjusts branch dampers so all terminals in a group share the same percentage of design flow before the group total is trimmed, preserving intended air distribution.

A probe with a total-pressure opening facing airflow and a static-pressure opening perpendicular to it; the difference between the two yields velocity pressure for calculating duct velocity and airflow.

The pressure exerted by moving air, equal to total pressure minus static pressure; its square root is proportional to velocity and is the basis for most duct airflow measurements.

The outward pressure air exerts perpendicular to duct walls, measured by a manometer or gauge and used to assess fan load, filter loading, and available pressure at terminals.

The sum of static and velocity pressure at a point in an air system, representing the total energy available to overcome downstream resistance.

A measurement procedure that averages velocity pressure readings across multiple points in a duct cross section to determine a representative average velocity and total airflow.

A calibrated capture device placed over a supply, return, or exhaust outlet that measures volumetric airflow directly and is the standard instrument for terminal balancing.

An instrument that measures pressure differential, often digital or inclined-liquid type, used for static pressure, filter drop, and fan performance readings during TAB work.

A velocity-measuring instrument, such as a rotating vane, thermal, or hot-wire type, used to check face velocities at coils, grilles, and open areas.

A movable blade or vane inside ductwork or at an outlet that restricts or redirects airflow; volume dampers are the primary adjustment device in air balancing.

A valve fitted with measurement ports and a calibrated setting indicator, allowing hydronic flow to be measured and locked at design value without guesswork.

Adjusting water flow through coils, branches, and pumps to design values using balancing valves, pressure readings, and pump curves so heat transfer matches design.

The difference in pressure between two points, such as across a coil, filter, or balancing valve; it is the key reading for determining water or air flow through a resistance.

A manufacturer's graph showing the relationship between flow and head for a pump; used to verify that measured pump operation matches design and to diagnose throttling or cavitation.

A manufacturer's graph relating airflow, static pressure, power, and efficiency for a fan; used to predict and confirm operating point after balancing adjustments.

A curve showing how the resistance of a duct or piping system varies with flow; its intersection with the fan or pump curve defines the actual operating point.

Relationships stating that airflow varies with speed, pressure with speed squared, and power with speed cubed; used to predict the effect of sheave or speed changes.

A grooved pulley on a fan or motor shaft whose diameter sets the belt-driven speed ratio; changing it is a common adjustment to correct airflow.

A terminal unit with a modulating damper and often a reheat coil that varies airflow to a zone in response to thermostat demand; balancing requires setting minimum and maximum flows.

The lowest airflow a VAV terminal is permitted to deliver, set to satisfy ventilation, heating, or fan-safety requirements and verified during balancing.

A control sequence that uses outdoor air for cooling when conditions allow; TAB must verify damper positions, linkage travel, and minimum outdoor-air settings.

Air drawn from outdoors for ventilation or free cooling; its quantity must be measured and set to meet code minimums and design intent during balancing.

Air extracted from conditioned spaces and conveyed back to the air handler; return airflow is measured and balanced so supply and return quantities are properly related.

Air deliberately removed from a space to the outdoors by fans or exhaust systems; balancing ensures it matches design and maintains intended space pressure relationships.

The pressure difference between indoors and outdoors, controlled by balancing supply, return, and exhaust air so the building is slightly positive or negative as designed.

A heat exchanger in an air handler or terminal that transfers heat between air and water or refrigerant; airflow and water flow across it must both be balanced.

The average air speed approaching a coil, filter, or grille face, calculated as airflow divided by face area and checked against design to avoid carryover or poor heat transfer.

The static pressure lost as air passes through a filter; measured during TAB to confirm clean-filter design drop and to set fan speed or alarm setpoints.

The difference between entering and leaving air or water temperatures across a coil or unit, used with flow to verify capacity and confirm balanced performance.

The measured noise at a space or terminal, often in A-weighted decibels; balancing can reduce noise by correcting excess airflow or velocity.

A pressurization test that quantifies air escaping from ductwork before balancing, ensuring measured system airflow reflects delivered airflow rather than losses.

Verification before balancing that equipment is installed, energized, and operable, filters are clean, dampers move freely, and controls respond, so measurements are valid.

A documented test confirming that systems and controls respond correctly under operating sequences, often performed after TAB to validate integrated performance.

The TAB deliverable documenting instruments used, measured versus design values, adjustments made, and deficiencies, serving as the record of certified system performance.