AFE Building Systems & Maintenance 2 — Questions and Answers
Question 1: A facility manager notices that a chiller's coefficient of performance (COP) has dropped from 5.2 to 3.8 over six months. What is the most likely cause?
- Refrigerant overcharge
- Condenser fouling reducing heat transfer (Correct answer)
- Evaporator operating at higher pressure
- Compressor running at excessive speed
Correct answer: Condenser fouling reducing heat transfer
Condenser fouling increases condensing temperature and pressure, reducing the COP by forcing the compressor to work harder.
Question 2: Which maintenance strategy uses real-time sensor data to trigger service actions only when equipment performance degrades beyond a threshold?
- Time-based preventive maintenance
- Predictive maintenance (Correct answer)
- Reactive maintenance
- Run-to-failure maintenance
Correct answer: Predictive maintenance
Predictive maintenance uses continuous monitoring data (vibration, temperature, oil analysis) to intervene before failure while avoiding unnecessary scheduled downtime.
Question 3: What does a building automation system (BAS) economizer cycle do during mild outdoor conditions?
- Increases chilled water temperature setpoint
- Uses outdoor air to provide free cooling instead of mechanical refrigeration (Correct answer)
- Bypasses the AHU filters to increase airflow
- Reduces supply air temperature by activating auxiliary cooling coils
Correct answer: Uses outdoor air to provide free cooling instead of mechanical refrigeration
An economizer cycle opens outdoor air dampers when outside enthalpy or temperature is favorable, reducing or eliminating mechanical cooling loads.
Question 4: A 120V single-phase motor draws 8 amps at full load. What is its approximate input power in watts?
- 640 W
- 880 W
- 960 W (Correct answer)
- 1,056 W
Correct answer: 960 W
Power (W) = Voltage × Current = 120V × 8A = 960 W for a purely resistive or unity power factor load.
Question 5: Which type of fire suppression system is best suited for a data center to minimize equipment damage?
- Wet pipe sprinkler
- Dry pipe sprinkler
- Clean agent (e.g., FM-200 or Novec 1230) (Correct answer)
- Deluge system
Correct answer: Clean agent (e.g., FM-200 or Novec 1230)
Clean agent systems suppress fires using gaseous agents that leave no residue and do not damage sensitive electronic equipment.
Question 6: What is the primary purpose of a pressure-reducing valve (PRV) in a building's domestic water system?
- Prevent backflow into the municipal supply
- Reduce high incoming water pressure to a safe distribution pressure (Correct answer)
- Control water temperature at fixtures
- Measure water consumption for billing
Correct answer: Reduce high incoming water pressure to a safe distribution pressure
A PRV reduces incoming street pressure (often 80–150 psi) to a safe domestic working pressure, typically 40–80 psi, protecting fixtures and piping.
Question 7: During an inspection, a facility engineer finds white crystalline deposits on the exterior of masonry walls. This condition is called:
- Spalling
- Efflorescence (Correct answer)
- Carbonation
- Delamination
Correct answer: Efflorescence
Efflorescence is caused by water moving through masonry and depositing soluble salts on the surface as it evaporates.
AFE Building Systems & Maintenance 2
A facility manager notices that a chiller's coefficient of performance (COP) has dropped from 5.2 to 3.8 over six months.
What is the most likely cause?