Precision Cooling Architecture Flashcards
7 cards from real ATP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Precision Cooling Architecture flashcards as text
What is the primary operational difference between a Computer Room Air Conditioner (CRAC) and a Computer Room Air Handler (CRAH)?
Answer: CRAC uses direct expansion refrigerant while CRAH uses chilled water coils
A CRAC unit contains its own DX refrigeration compressor, while a CRAH relies on an external chilled water plant and uses water-cooled coils.
In-row cooling units are deployed specifically to address which data center challenge?
Answer: Delivering cooling close to high-density heat loads with shorter airflow paths
In-row coolers are placed between server racks to shorten airflow paths, reducing mixing and improving cooling effectiveness for high-density deployments.
Which cooling metric expresses a precision cooling unit's ability to remove heat relative to its total power consumption?
Answer: COP (Coefficient of Performance)
COP is the ratio of useful cooling output to electrical energy input; a higher COP indicates a more efficient unit.
A Sensible Heat Ratio (SHR) near 1.0 in a precision cooling unit indicates what?
Answer: The unit is removing mostly sensible (temperature) heat
Precision cooling units are designed with high SHR (close to 1.0) because IT equipment generates mostly sensible heat, not latent heat.
When sizing a precision cooling system, which factor is most commonly used to express the total cooling load?
Answer: kW or tons of refrigeration based on IT load
Data center cooling capacity is sized in kW or tons directly matched to the total IT power load, since nearly all IT power converts to heat.
What is the recommended supply air temperature range for data center cooling according to ASHRAE A1 equipment class guidelines?
Answer: 64.4–80.6°F (18–27°C)
ASHRAE A1 specifies an allowable inlet temperature range of 59–89.6°F, but recommended supply temperatures generally target 64.4–80.6°F (18–27°C) for energy efficiency.
Overhead or ceiling-mounted precision cooling units typically supply cooled air in which direction relative to IT equipment?
Answer: Downward into the cold aisle or directly onto equipment tops
Overhead cooling units direct conditioned air downward into cold aisles or onto equipment, complementing or replacing raised-floor airflow distribution.