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, a terminal unit serving a conference room measures 15% above design airflow even with the balancing damper fully closed. What does this indicate?
Answer: Excess system static pressure requires main duct damper adjustment or rescheduling
When a terminal damper fully closed still passes excess air, system static pressure is too high and must be reduced by adjusting main balancing dampers or fan speed.
What commissioning activity is performed to verify that heating and cooling systems do not operate simultaneously (simultaneous heating and cooling)?
Answer: Sequence of operations functional test across all operating modes
Functional testing of the control sequence across all operating modes identifies simultaneous heating and cooling, a common energy waste and control deficiency.
Which measurement is required to calculate the actual outside air percentage delivered to an air handling unit during TAB?
Answer: Mixed air, return air, and outside air CO2 or temperature readings for mass balance
Outside air percentage is calculated using a three-point temperature or CO2 mass balance comparing outside air, return air, and mixed air conditions.
A heat recovery wheel in an energy recovery ventilator (ERV) shows only 50% of design sensible effectiveness during functional testing. What is the most likely cause?
Answer: Wheel rotation failure, bypass leakage, or purge sector misalignment
Low sensible effectiveness in a rotary heat exchanger is commonly caused by wheel not rotating, air bypassing through seals, or incorrect purge sector positioning.
During commissioning of a chilled water plant, what does a high approach temperature across the cooling tower indicate?
Answer: Fouling, inadequate airflow, or reduced water distribution reducing heat rejection
High approach temperature (condenser water leaving minus outdoor wet-bulb) indicates tower performance degradation from fouling, scaling, inadequate fan airflow, or plugged distribution nozzles.
What is the primary reason for performing TAB before commissioning functional testing?
Answer: Proper airflow and waterflow are prerequisites for controls to function correctly during functional testing
Controls cannot respond correctly if flows are not at design values — TAB establishes the physical baseline that makes functional testing results meaningful and valid.
When documenting TAB results for a multi-zone AHU serving 40 VAV boxes, which condition requires immediate notification to the commissioning authority?
Answer: Ten or more boxes unable to achieve minimum airflow setpoint due to a common cause deficiency
A systematic deficiency affecting multiple terminals that prevents minimum airflow achievement is a code compliance and indoor air quality risk requiring immediate escalation to the commissioning authority.