C7 Energy Management & Building Automation 2 — Questions and Answers
Question 1: In a BAS, what does the term 'setpoint' refer to?
- The maximum rated voltage of a controller
- The target value a control system attempts to maintain (Correct answer)
- The physical mounting location of a sensor
- The communication baud rate between devices
Correct answer: The target value a control system attempts to maintain
A setpoint is the desired target value (e.g., temperature, humidity) that a building automation controller regulates toward.
Question 2: Which protocol is most commonly used for peer-to-peer communication between BAS field controllers over a twisted-pair network?
- Modbus RTU
- BACnet MS/TP (Correct answer)
- DALI
- KNX TP
Correct answer: BACnet MS/TP
BACnet MS/TP (Master-Slave/Token-Passing) is widely used for field-level controller communication over RS-485 twisted-pair wiring.
Question 3: A demand-controlled ventilation (DCV) system modulates outdoor airflow based on readings from which sensor type?
- Occupancy motion sensors
- CO2 concentration sensors (Correct answer)
- Volatile organic compound sensors
- Barometric pressure sensors
Correct answer: CO2 concentration sensors
DCV systems use CO2 sensors as a proxy for occupancy to adjust outdoor air damper positions and maintain acceptable indoor air quality.
Question 4: What is the primary purpose of a 'dead band' in HVAC control logic?
- To prevent communication collisions on the BAS network
- To create a neutral zone where neither heating nor cooling is active (Correct answer)
- To limit the maximum current draw of a VFD
- To define the polling interval for energy meters
Correct answer: To create a neutral zone where neither heating nor cooling is active
A dead band is a range between heating and cooling setpoints where no conditioning occurs, preventing equipment short-cycling.
Question 5: Under California Title 24 Part 6, automatic daylighting controls must turn off or reduce electric lighting when daylight levels are sufficient in which type of spaces?
- Server rooms and data centers
- Primary sidelighted and toplit areas (Correct answer)
- Stairwells and corridors only
- Parking garages below grade
Correct answer: Primary sidelighted and toplit areas
Title 24 Part 6 requires automatic daylighting controls in primary sidelighted and toplit areas to reduce energy consumption from electric lighting.
Question 6: A variable frequency drive (VFD) reduces motor energy consumption primarily by:
- Increasing the power factor to unity at all loads
- Varying the supply frequency to match required motor speed (Correct answer)
- Switching the motor between star and delta winding configurations
- Storing regenerative energy in supercapacitors
Correct answer: Varying the supply frequency to match required motor speed
VFDs control motor speed by varying the frequency of the AC supply, and since fan/pump power varies with the cube of speed, even small speed reductions yield large energy savings.
Question 7: In a BAS graphical user interface, an 'alarm acknowledgment' action indicates that an operator has:
- Permanently resolved the fault condition
- Silenced the audible notification and confirmed awareness of the alarm (Correct answer)
- Reset the field device to factory defaults
- Disabled the affected control loop indefinitely
Correct answer: Silenced the audible notification and confirmed awareness of the alarm
Acknowledging an alarm confirms the operator is aware of the condition; the alarm may remain active until the fault is cleared.
C7 Energy Management & Building Automation 2
In a BAS, what does the term 'setpoint' refer to?