C7 Energy Management & Building Automation 3 — Questions and Answers
Question 1: What wiring topology does KNX TP (twisted pair) typically use for field devices?
- Strict daisy-chain only
- Free topology (bus, star, tree, or combination) (Correct answer)
- Ring topology with redundant paths
- Mesh topology with automatic route discovery
Correct answer: Free topology (bus, star, tree, or combination)
KNX TP supports free topology, allowing installers to wire devices in bus, star, tree, or mixed configurations within segment length limits.
Question 2: An energy management system (EMS) implements 'load rolling' to:
- Rotate which electrical loads are shed during peak demand periods (Correct answer)
- Balance three-phase voltage across distribution panels
- Schedule battery storage charging during off-peak hours
- Calibrate energy meters at regular intervals
Correct answer: Rotate which electrical loads are shed during peak demand periods
Load rolling cycles the shutdown of non-critical loads in sequence during peak demand events so no single area is without service for extended periods.
Question 3: Which California energy code provision requires newly installed lighting controls to include a manual-on function limited to a specific zone area?
- Title 24 Part 4 Section 407
- Title 24 Part 6 Section 130.1 occupancy sensor requirements (Correct answer)
- Title 20 appliance efficiency regulations
- CALGreen mandatory measures Section 5.106
Correct answer: Title 24 Part 6 Section 130.1 occupancy sensor requirements
Title 24 Part 6 Section 130.1 governs indoor lighting controls and specifies occupancy sensor requirements including manual-on functionality and zone area limits.
Question 4: A BAS supervisor discovers that a field controller's real-time clock has drifted by 45 minutes. What is the most likely effect on the system?
- Loss of communication with the supervisory controller
- Schedules executing at incorrect times, causing energy waste or comfort complaints (Correct answer)
- Sensors reporting out-of-range values due to timing errors
- Automatic reset of all PID control loop parameters
Correct answer: Schedules executing at incorrect times, causing energy waste or comfort complaints
An incorrect clock causes time-based schedules (occupancy, setpoint shifts, lighting scenes) to run at wrong times, degrading energy performance and occupant comfort.
Question 5: In a chilled water system, 'chiller sequencing' logic in a BAS is used to:
- Alternate which chiller starts first to equalize run hours
- Determine the order and number of chillers to enable based on cooling load (Correct answer)
- Stagger motor starts to limit inrush current on the electrical system
- Balance refrigerant charge between multiple chiller units
Correct answer: Determine the order and number of chillers to enable based on cooling load
Chiller sequencing optimizes efficiency by staging chillers on and off based on real-time cooling demand rather than running all units at partial load.
Question 6: What is the function of a 'trend log' in a building automation system?
- A record of technician login and logout events for auditing
- A time-stamped history of a data point's values for analysis and diagnostics (Correct answer)
- A list of all devices discovered on the BAS network
- A log of firmware update events for field controllers
Correct answer: A time-stamped history of a data point's values for analysis and diagnostics
Trend logs capture periodic or change-of-value snapshots of BACnet or other data points, enabling energy analysis, fault detection, and commissioning verification.
Question 7: A low-voltage lighting control relay panel used in a C7 installation must be listed and labeled under which standard for branch circuit rated relays?
- UL 508A (Industrial Control Panels)
- UL 924 (Emergency Lighting Equipment)
- UL 508 or UL 916 for energy management equipment (Correct answer)
- UL 1449 (Surge Protective Devices)
Correct answer: UL 508 or UL 916 for energy management equipment
Lighting control relay panels and energy management equipment are typically listed under UL 508 (industrial controls) or UL 916 (energy management equipment).
C7 Energy Management & Building Automation 3
What wiring topology does KNX TP (twisted pair) typically use for field devices?