CCP HVAC TAB & Functional Testing 2

Question 1

During TAB, an air handler's measured total airflow is 10% below design. What is the FIRST corrective action to investigate?

Accepted Answer

Check and adjust variable frequency drive speed settings

Answer

VFD speed settings are the first adjustment point when measured airflow is below design, as they directly control fan RPM without physical modification.

Question 2

What does a negative static pressure reading at the supply plenum of an air handler indicate?

Accepted Answer

Potential fan rotation issue or severe restriction upstream

Answer

Negative static pressure at the supply plenum suggests fan reverse rotation, severe upstream restriction, or significant duct leakage pulling air back.

Question 3

Which instrument is most appropriate for measuring airflow velocity in a large rectangular duct during TAB?

Accepted Answer

Pitot tube traverse with manometer

Answer

A Pitot tube traverse across a grid of points in the duct provides the most accurate average velocity measurement for large rectangular ducts.

Question 4

During functional testing of a VAV system, what parameter must be verified at minimum airflow setpoint?

Accepted Answer

Adequate ventilation per ASHRAE 62.1 requirements

Answer

At minimum airflow setpoint, each VAV box must still deliver sufficient outside air to meet ASHRAE 62.1 ventilation requirements for occupants.

Question 5

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?

Accepted Answer

Coil bypassing due to fouling or air entrainment

Answer

Coil fouling, scaling, or air binding reduces heat transfer surface contact, causing leaving air temperature to exceed design despite correct water conditions.

(CCP) Certified Commissioning Professional Practice Test

(CCP) Certified Commissioning Professional Practice Test

CCP HVAC TAB & Functional Testing 2