CDCP Cooling and Environmental Control 5 — Questions and Answers
Question 1: What is the main advantage of a waterside economizer over an airside economizer in a data center?
- It requires no cooling towers
- It eliminates the need for humidity control
- It does not introduce outside contaminants into the data center (Correct answer)
- It operates at higher outdoor temperatures
Correct answer: It does not introduce outside contaminants into the data center
Waterside economizers cool water via a cooling tower or dry cooler and then use that water in the chiller loop, keeping outside air out of the IT space.
Question 2: A data center manager notices the return air temperature to the CRAC units is unusually low. What does this most likely indicate?
- The servers are running at full load
- Excessive cold air bypass (short-cycling) (Correct answer)
- The cooling plant is undersized
- The humidity level is too high
Correct answer: Excessive cold air bypass (short-cycling)
Low return air temperature indicates cold supply air is bypassing IT equipment and returning directly to the cooling unit without absorbing heat.
Question 3: In immersion cooling for data centers, what fluid is typically used to submerge IT equipment?
- Distilled water
- Dielectric fluid (Correct answer)
- Ethylene glycol
- Isopropyl alcohol
Correct answer: Dielectric fluid
Dielectric (electrically non-conductive) fluids are used in immersion cooling so the liquid can safely contact live electronic components.
Question 4: What is the effect of raising the cold aisle temperature set point from 65°F to 75°F in a modern data center with ASHRAE A1-rated equipment?
- IT equipment warranty is immediately voided
- Chiller efficiency improves, reducing energy consumption (Correct answer)
- CRAC units must work harder, increasing energy use
- Server fan speeds automatically decrease, raising failure rates
Correct answer: Chiller efficiency improves, reducing energy consumption
A higher cold aisle set point allows chillers to operate at warmer chilled water temperatures, which significantly improves chiller COP and saves energy.
Question 5: Which organization publishes the widely adopted thermal guidelines (A1–A4 classes) for data center IT equipment?
- IEEE
- ASHRAE (Correct answer)
- TIA
- BICSI
Correct answer: ASHRAE
ASHRAE's Technical Committee 9.9 publishes the thermal guidelines, including the A1–A4 equipment classes used globally.
Question 6: What is the primary risk of allowing relative humidity to drop below 20% in a data center?
- Condensation on equipment
- Increased electrostatic discharge (ESD) risk (Correct answer)
- Corrosion of copper bus bars
- Mold growth on server components
Correct answer: Increased electrostatic discharge (ESD) risk
Very low humidity increases static charge buildup, raising the risk of electrostatic discharge that can damage sensitive electronic components.
Question 7: A data center operator wants to maximize free cooling hours annually. Which geographic or site factor has the greatest influence?
- Proximity to a fiber backbone
- Local climate and annual dry-bulb temperature distribution (Correct answer)
- Altitude above sea level only
- Predominant wind direction
Correct answer: Local climate and annual dry-bulb temperature distribution
The local climate's dry-bulb temperature distribution determines how many hours per year outdoor conditions are cool enough to support economizer operation.
CDCP Cooling and Environmental Control 5
What is the main advantage of a waterside economizer over an airside economizer in a data center?