Exin CDCS Exam Dumps

From an efficiency standpoint, Unit B with a Sensible Heat Ratio (SHR) of 0.9 is preferable. A higher SHR indicates that a greater proportion of the air conditioner's capacity is dedicated to sensible cooling (temperature reduction) rather than latent cooling (moisture removal). In data centers, sensible cooling is more critical since IT equipment primarily generates heat without adding significant moisture.

Detailed Explanation:

An SHR of 0.9 means that 90% of the cooling capacity is used for sensible cooling, which is more efficient for environments like data centers where humidity control is typically less of a concern. Opting for an air conditioner with a higher SHR ensures that most of the cooling energy is focused on temperature reduction, making Unit B more efficient in this scenario.

EPI Data Center Specialist Reference:

EPI data center best practices recommend choosing cooling units with higher SHR values in data centers, as they better match the cooling needs of IT equipment. High SHR units improve cooling efficiency by concentrating on sensible heat removal, which is vital for maintaining the optimal thermal environment.

Battery charging current is typically sized at 10% of the total Ah capacity to ensure safe charging without overheating.

ChargingCurrent=800Ah0.1=80A

40 A or 60 A would undercharge, extending recovery time after discharge.

160 A would be too high, causing heat and reducing battery life.

Thus, 80 A is correct.

When calculating Power Usage Effectiveness (PUE) in a data center that uses chilled water from an external source, like from a building owner, a weight factor for district chilled water must be applied. This is because PUE calculations aim to measure the energy efficiency of the data center's own operations, and external utilities like district chilled water aren't directly powered by the data center. A weight factor of 0.4 is typically used to account for the energy consumed to produce and deliver the chilled water, reflecting the indirect impact on the data center's total energy consumption.

Detailed Explanation:

PUE is calculated as the ratio of the total facility energy to the IT equipment energy. If the cooling is provided by an external chilled water source, it's necessary to adjust the calculations to accurately reflect the energy impact. By incorporating the 0.4 weight factor, data centers can calculate a more accurate PUE, aligning with standard methods and industry best practices.

EPI Data Center Specialist Reference:

EPI training on PUE highlights the importance of adjusting for external energy sources, such as district cooling, in the calculations. This ensures that PUE values remain accurate and comparable across different data centers, even when external utilities are used.

In a wet pipe system, the piping is always filled with water under pressure. When a sprinkler head is triggered by heat, water is discharged immediately. This is the most common sprinkler system for general buildings.

Dry pipe: Pipes contain air or nitrogen; water enters only after valve activation.

Deluge: Pipes are empty, and all heads open simultaneously, releasing water everywhere.

Pre-action: Pipes are dry until detection and valve activation; reduces accidental discharge risk, recommended for IT rooms.

Since the definition describes immediate discharge from water-filled pipes, this is a wet pipe system.

Hypoxic systems continuously lower oxygen concentration (~15%) to prevent combustion. While safe for short-term human exposure, standards like ISO 20338 recommend they are not suitable for continuously occupied spaces, because reduced oxygen may cause fatigue, reduced cognition, and health risks for staff.

B is irrelevant---air change rates affect dilution, not feasibility.

C is incorrect---tanks can be remote.

D is false---positive pressure is not required.

Thus, the main disadvantage is restriction to non-continuous occupancy.