CBCP CBCP Building Automation & Control Systems 2 — Questions and Answers
Question 1: What is the purpose of a 'trend log' in a BAS during commissioning?
- Recording occupant complaints
- Logging historical data of control variables over time to verify system performance (Correct answer)
- Tracking maintenance work orders
- Storing emergency contact numbers
Correct answer: Logging historical data of control variables over time to verify system performance
Trend logs capture time-stamped data for sensors and control outputs, allowing commissioning agents to verify proper system behavior over time.
Question 2: A VAV (Variable Air Volume) box fails to modulate during FPT. Which BAS component should the commissioning agent check first?
- The chiller compressor
- The DDC controller output signal to the VAV actuator (Correct answer)
- The cooling tower basin level
- The building electrical main breaker
Correct answer: The DDC controller output signal to the VAV actuator
The DDC controller output signal drives the VAV actuator, so verifying this signal is the logical first diagnostic step.
Question 3: Which ASHRAE guideline specifically addresses the commissioning process for HVAC&R systems?
- ASHRAE 90.1
- ASHRAE Guideline 0 (Correct answer)
- ASHRAE 62.1
- ASHRAE 55
Correct answer: ASHRAE Guideline 0
ASHRAE Guideline 0 defines the commissioning process for new and existing buildings across all systems.
Question 4: What does the term 'sequence of operations' refer to in a BAS?
- The order in which construction trades install equipment
- A written description of how control systems respond to various inputs and conditions (Correct answer)
- The startup order for electrical panels
- The maintenance schedule for air handlers
Correct answer: A written description of how control systems respond to various inputs and conditions
The sequence of operations is the narrative description of how the BAS controls equipment under various conditions and modes.
Question 5: An AHU economizer damper is found fully closed during a 40°F outdoor air temperature condition when free cooling should be available. Which BAS parameter should be reviewed?
- Chilled water differential pressure setpoint
- Economizer changeover (enable) setpoint (Correct answer)
- VAV box minimum airflow setpoint
- Duct static pressure setpoint
Correct answer: Economizer changeover (enable) setpoint
The economizer changeover setpoint determines the outdoor air temperature or enthalpy threshold at which economizer mode is enabled.
Question 6: What is the purpose of a 'hardwired interlock' in a BAS control system?
- To provide a software-independent safety shutdown that activates regardless of the BAS program (Correct answer)
- To link two VAV boxes together for coordinated control
- To synchronize BAS communication protocols
- To set a shared setpoint across multiple zones
Correct answer: To provide a software-independent safety shutdown that activates regardless of the BAS program
Hardwired interlocks provide a fail-safe, BAS-independent layer of protection that cannot be overridden by software errors.
CBCP CBCP Building Automation & Control Systems 2
What is the purpose of a 'trend log' in a BAS during commissioning?