CEA Energy Auditing & Assessment Techniques 3 — Questions and Answers
Question 1: Infrared thermography during an energy audit is most effective for identifying:
- Insulation voids, moisture intrusion, and thermal bridging in the building envelope (Correct answer)
- Electrical panel overloads and circuit breaker faults
- Combustion efficiency of boilers and furnaces
- Refrigerant leaks in HVAC refrigeration circuits
Correct answer: Insulation voids, moisture intrusion, and thermal bridging in the building envelope
Infrared cameras detect surface temperature differences that reveal missing insulation, air leakage, and moisture—all of which degrade envelope performance.
Question 2: In motor systems assessment, what is the significance of measuring 'motor load factor'?
- It reveals whether a motor is oversized for its application, indicating downsizing or VFD opportunities (Correct answer)
- It determines the motor's insulation class rating
- It calculates the cost of reactive power penalties
- It identifies whether the motor meets NEMA Premium efficiency standards
Correct answer: It reveals whether a motor is oversized for its application, indicating downsizing or VFD opportunities
A motor running at low load factor (below 50%) wastes energy; right-sizing or adding a VFD can dramatically reduce consumption.
Question 3: A retro-commissioning (RCx) study differs from a traditional energy audit primarily because RCx:
- Focuses on optimizing existing systems to restore original design performance without capital upgrades (Correct answer)
- Requires full equipment replacement as part of its scope
- Only addresses lighting and plug loads
- Is conducted exclusively on new buildings before occupancy
Correct answer: Focuses on optimizing existing systems to restore original design performance without capital upgrades
Retro-commissioning identifies operational deficiencies in existing equipment (e.g., simultaneous heating and cooling) and corrects them for low/no-cost savings.
Question 4: When auditing a compressed air system, which condition represents the GREATEST source of energy waste?
- System leaks, which can account for 20–30% of compressor output (Correct answer)
- Slightly elevated discharge pressure above design set point
- Use of reciprocating rather than rotary screw compressors
- Lack of an air dryer on the distribution system
Correct answer: System leaks, which can account for 20–30% of compressor output
Compressed air leaks are the single largest waste source in industrial systems, often wasting 20–30% of total compressed air production.
Question 5: During an HVAC audit, the auditor finds an air handling unit with simultaneous heating and cooling (hot deck/cold deck mixing). The recommended corrective action is to:
- Reset the hot deck and cold deck temperatures using an outdoor air reset schedule to minimize mixing (Correct answer)
- Replace the AHU with a variable air volume (VAV) system immediately
- Reduce cooling set points to minimize heating demand
- Install CO₂ sensors to control outdoor air intake
Correct answer: Reset the hot deck and cold deck temperatures using an outdoor air reset schedule to minimize mixing
Optimizing hot and cold deck temperature reset schedules reduces simultaneous heating/cooling energy waste, a classic low-cost retro-commissioning measure.
Question 6: A 'degree-day analysis' is used in energy auditing to:
- Normalize heating and cooling energy consumption against outdoor temperature variation across years (Correct answer)
- Calculate the solar heat gain through fenestration systems
- Determine the efficiency of domestic hot water heating equipment
- Size mechanical ventilation equipment for a given climate zone
Correct answer: Normalize heating and cooling energy consumption against outdoor temperature variation across years
Degree-day normalization allows auditors to compare energy use across different weather years and separate weather-related variation from operational changes.
Question 7: The 'simple payback period' for an energy conservation measure (ECM) is calculated as:
- Initial capital cost divided by annual energy cost savings (Correct answer)
- Annual energy cost savings multiplied by equipment life
- Net present value of savings divided by discount rate
- Total lifetime savings minus installation cost
Correct answer: Initial capital cost divided by annual energy cost savings
Simple payback = Capital Cost ÷ Annual Savings; it is a quick screening metric but ignores time value of money and equipment life.
CEA Energy Auditing & Assessment Techniques 3
Infrared thermography during an energy audit is most effective for identifying: