Exin EPI Certified Data Centre Specialist CDCS Exam Questions

Answer : B

MCBs (Miniature Circuit Breakers) are characterized by their tripping curves:

B-Curve: Trips at 3--5 rated current; suitable for resistive loads.

C-Curve: Trips at 5--10 rated current; suitable for mixed loads including ICT equipment with moderate inrush current.

D-Curve: Trips at 10--20 rated current; used for heavy inductive loads like motors.

A-Curve: Very sensitive, rarely used outside specialty electronics.

Since ICT equipment like servers and network devices have moderate inrush currents (from power supplies), the recommended breaker is C-Curve. It balances protection against nuisance tripping while still ensuring fault clearance.

Answer : B

The aisle pitch is the total width of a rack row plus cold aisle plus rack row. For 1.0 m racks on each side with cold aisle containment, ASHRAE and TIA-942 recommend the 7-tile rule (each tile ~0.6 m). This ensures enough width for equipment clearance, airflow distribution, and human access.

5-tile pitch is too narrow, restricting containment effectiveness.

8--10 tiles may be used in some hyperscale layouts but are not standard for 1 m racks.

Thus, the correct design recommendation is the 7 tiles pitch rule.

Answer : A

Electromagnetic field (EMF) strength around cables is primarily influenced by current, not voltage. In a single-phase system, the live and neutral conductors are separated, creating a larger magnetic loop area. This produces stronger stray EMF when current increases.

In a balanced three-phase system, the magnetic fields from the three conductors largely cancel each other out, resulting in much lower net EMF, even at higher currents.

Therefore, the correct statement is that increasing current in single-phase cables produces higher EMF compared to three-phase cables. Options B, C, and D incorrectly link EMF to voltage or incorrect current behavior.

Answer : B

The most effective EMF mitigation is to install shielding as close as possible to the source of radiation. By blocking or redirecting magnetic flux at the origin (the transformer room walls), the overall field propagation into adjacent areas is minimized. If shielding were placed at the computer room, the field would already have spread over the intervening space, requiring more material and higher cost.

Standards such as IEEE Std 299 (EMC Shielding Effectiveness) and IEC 61000 emphasize source-based mitigation. Additionally, ANSI/TIA-942 requires EMF shielding where magnetic flux exceeds recommended ICT thresholds (generally <5 mG for sensitive tape/disk storage).

Although 100 mG is often tolerated by modern equipment, legacy magnetic storage can be affected, so shielding is still prudent. Hence, the correct location is at the transformer room wall.

Answer : A

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.

Answer : D

Testing smoke sensors should be conducted according to the vendor specifications to ensure compliance with safety standards and accurate results. Vendors provide specific testing procedures to account for the sensor type, environment, and operational characteristics, ensuring that tests do not damage the equipment or provide false results.

Detailed Explanation:

Smoke sensors can vary by type and sensitivity, so following the vendor's recommended testing procedure ensures the sensors function correctly without risking sensor damage. Injecting smoke or using a self-test might be insufficient or could lead to inaccurate assessments if they do not align with the vendor's testing protocol.

EPI Data Center Specialist Reference:

EPI recommends adhering to manufacturer specifications for testing critical safety equipment, ensuring that tests reflect real-world conditions without compromising sensor integrity or reliability.

Answer : B

Hot and cold aisle containment prevents mixing of supply and return air, which improves cooling efficiency. By maintaining higher return-air temperatures, cooling units operate more efficiently, often allowing higher chilled water setpoints. This reduces overall cooling power consumption, directly improving PUE (Power Usage Effectiveness).

Containment is recognized by ASHRAE and Green Grid as one of the simplest and most cost-effective methods for lowering PUE. Options A, C, and D are false because containment benefits apply regardless of cooling source or IT virtualization.