HVAC TAB & Functional Testing Flashcards
7 cards from real CCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 HVAC TAB & Functional Testing flashcards as text
During TAB, an air handler's measured total airflow is 10% below design. What is the FIRST corrective action to investigate?
Answer: Check and adjust variable frequency drive speed settings
VFD speed settings are the first adjustment point when measured airflow is below design, as they directly control fan RPM without physical modification.
What does a negative static pressure reading at the supply plenum of an air handler indicate?
Answer: Potential fan rotation issue or severe restriction upstream
Negative static pressure at the supply plenum suggests fan reverse rotation, severe upstream restriction, or significant duct leakage pulling air back.
Which instrument is most appropriate for measuring airflow velocity in a large rectangular duct during TAB?
Answer: Pitot tube traverse with manometer
A Pitot tube traverse across a grid of points in the duct provides the most accurate average velocity measurement for large rectangular ducts.
During functional testing of a VAV system, what parameter must be verified at minimum airflow setpoint?
Answer: Adequate ventilation per ASHRAE 62.1 requirements
At minimum airflow setpoint, each VAV box must still deliver sufficient outside air to meet ASHRAE 62.1 ventilation requirements for occupants.
A chilled water coil leaving air temperature is 5°F above design during TAB. The entering water temperature and flow are correct. What is the most likely cause?
Answer: Coil bypassing due to fouling or air entrainment
Coil fouling, scaling, or air binding reduces heat transfer surface contact, causing leaving air temperature to exceed design despite correct water conditions.
What is the purpose of the traverse method when measuring duct airflow with a Pitot tube?
Answer: To account for non-uniform velocity distribution across the duct cross-section
The traverse method uses multiple measurement points across the duct cross-section to capture velocity variations and calculate accurate average airflow.
During TAB documentation, what must be recorded when a system cannot be balanced to within acceptable tolerances?
Answer: Deficiency report identifying cause and recommended corrective action
NEBB and AABC standards require formal deficiency reports that identify the cause of unacceptable results and recommend specific corrective actions.