AFE Building Systems & Maintenance 4 — Questions and Answers
Question 1: Under ASHRAE Standard 90.1, what is the primary purpose of demand-controlled ventilation (DCV)?
- Maintain constant supply air temperature
- Reduce outdoor air intake when occupancy is low, saving heating and cooling energy (Correct answer)
- Increase static pressure in VAV systems during peak loads
- Control CO levels in parking garages
Correct answer: Reduce outdoor air intake when occupancy is low, saving heating and cooling energy
DCV uses CO₂ sensors to modulate outdoor air intake based on actual occupancy, reducing energy wasted conditioning unnecessary outdoor air in partially occupied spaces.
Question 2: A facility engineer is sizing a domestic hot water heater. What parameter is most critical for determining peak demand capacity?
- Average daily water consumption
- Peak hourly draw rate and recovery rate (Correct answer)
- Fuel type and efficiency rating
- Pipe diameter to the farthest fixture
Correct answer: Peak hourly draw rate and recovery rate
Peak hourly demand determines the required storage and recovery rate; undersizing based on average use leads to inadequate hot water during high-demand periods.
Question 3: Which lubrication method is most suitable for a high-speed centrifugal pump bearing operating continuously at elevated temperatures?
- Grease lubrication with manual regreasing every 30 days
- Oil mist lubrication or circulating oil system (Correct answer)
- Dry PTFE film lubricant
- Monthly splash-oil bath without circulation
Correct answer: Oil mist lubrication or circulating oil system
Circulating oil or oil mist systems provide continuous cooling and contamination removal for high-speed, high-temperature bearings where grease would degrade rapidly.
Question 4: When performing a roof infrared scan to detect moisture intrusion, when should the scan be conducted for best results?
- Midday when sun exposure is maximum
- Shortly after sunset while the roof is cooling and wet areas retain heat (Correct answer)
- Early morning before sunrise
- Immediately after a rainstorm
Correct answer: Shortly after sunset while the roof is cooling and wet areas retain heat
After sunset, dry roofing materials cool faster than moisture-saturated areas, creating thermal contrast detectable by infrared cameras.
Question 5: A building's water treatment program specifies maintaining 300–500 ppm total dissolved solids (TDS) in the cooling tower basin. What control method is most commonly used to manage TDS?
- Increasing biocide dosing frequency
- Blowdown (bleed-off) of concentrated tower water and replacement with fresh makeup water (Correct answer)
- Adding scale inhibitor above the normal dosing rate
- Reducing fan speed to lower evaporation rate
Correct answer: Blowdown (bleed-off) of concentrated tower water and replacement with fresh makeup water
Blowdown removes concentrated water from the system, lowering TDS and cycles of concentration, and is replaced by fresh makeup water to dilute dissolved solids.
Question 6: What does a high differential pressure reading across an air handler's supply fan indicate when airflow has decreased?
- The fan belt is slipping, reducing efficiency
- The supply air filters are loaded and need replacement (Correct answer)
- The supply fan motor is drawing too little current
- The chilled water valve is fully closed
Correct answer: The supply air filters are loaded and need replacement
A clogged filter increases resistance on the suction side, raising the pressure differential across the fan section while reducing actual airflow delivered.
Question 7: A facility manager is implementing an energy audit per ASHRAE Level II standards. Which deliverable distinguishes a Level II from a Level I audit?
- Walk-through assessment with utility bill analysis only
- Detailed energy analysis with capital cost estimates and savings for specific measures (Correct answer)
- Monitoring and verification of previously implemented measures
- Benchmark comparison to similar facilities using ENERGY STAR
Correct answer: Detailed energy analysis with capital cost estimates and savings for specific measures
A Level II audit goes beyond the walk-through by providing engineering analysis, detailed energy savings calculations, and capital cost estimates for each identified energy conservation measure.
AFE Building Systems & Maintenance 4
Under ASHRAE Standard 90.1, what is the primary purpose of demand-controlled ventilation (DCV)?