CDCP Cooling and Environmental Control 4 — Questions and Answers
Question 1: What is the primary purpose of a containment system (hot aisle/cold aisle containment) in a data center?
- Reduce noise levels from CRAC units
- Prevent mixing of hot exhaust and cold supply air (Correct answer)
- Increase the number of servers per rack
- Simplify cable management
Correct answer: Prevent mixing of hot exhaust and cold supply air
Containment systems physically separate hot exhaust air from cold supply air, dramatically improving cooling efficiency.
Question 2: In a data center, what does CRAH stand for?
- Computer Room Air Handler (Correct answer)
- Cooling Refrigerant Airflow Hub
- Central Room Air Humidity controller
- Computer Rack Air Humidifier
Correct answer: Computer Room Air Handler
CRAH (Computer Room Air Handler) uses chilled water coils—rather than refrigerant like CRAC units—to cool the air.
Question 3: Which metric is used to measure the efficiency of a data center's cooling system relative to total IT load?
- PUE
- ERE
- COP (Correct answer)
- CADE
Correct answer: COP
COP (Coefficient of Performance) specifically measures cooling efficiency as the ratio of cooling output to electrical energy input.
Question 4: What is the recommended approach when a data center experiences hot spots despite adequate overall cooling capacity?
- Lower the thermostat set point for all CRAC units
- Add blanking panels and seal cable cutouts in affected racks (Correct answer)
- Increase server fan speeds via BIOS settings
- Relocate the CRAC unit nearest to the hot spot
Correct answer: Add blanking panels and seal cable cutouts in affected racks
Blanking panels and sealed cutouts prevent bypass airflow and recirculation, directing cold air where it is needed.
Question 5: A data center is transitioning to a higher rack power density of 20 kW per rack. Which cooling approach is most likely required?
- Raised-floor plenum with perforated tiles only
- In-row or rear-door heat exchanger cooling (Correct answer)
- Increased CRAC unit fan speed
- Wider cold aisle spacing
Correct answer: In-row or rear-door heat exchanger cooling
High-density racks (above ~10 kW) typically require in-row or rear-door heat exchangers to remove heat closer to the source.
Question 6: What is the ASHRAE A1 thermal envelope's recommended inlet temperature range for IT equipment?
- 50°F–59°F (10°C–15°C)
- 64.4°F–80.6°F (18°C–27°C) (Correct answer)
- 41°F–68°F (5°C–20°C)
- 59°F–77°F (15°C–25°C)
Correct answer: 64.4°F–80.6°F (18°C–27°C)
ASHRAE A1 specifies an allowable inlet temperature range of 59°F–80.6°F (15°C–27°C), with 64.4°F–80.6°F as the recommended range.
Question 7: Which type of economizer cooling uses outdoor air directly to cool the data center without mechanical refrigeration during favorable weather?
- Waterside economizer
- Airside economizer (Correct answer)
- Evaporative economizer
- Indirect evaporative cooler
Correct answer: Airside economizer
Airside economizers draw in cool outdoor air directly into the data center, bypassing the chiller when conditions permit.
CDCP Cooling and Environmental Control 4
What is the primary purpose of a containment system (hot aisle/cold aisle containment) in a data center?