Exin EPI Certified Data Centre Specialist CDCS Exam Practice Test

Answer : D

Relative Humidity (RH) is defined as the ratio of the actual water vapor content in the air to the maximum possible water vapor content at a given temperature. To calculate RH:

Dry bulb temperature (DBT): the ambient air temperature.

Wet bulb temperature (WBT): the temperature measured by a thermometer covered with a wet wick, influenced by evaporative cooling.

Using DBT and WBT, the humidity ratio and dew point can be determined with a psychrometric chart or Mollier diagram. From there, RH is calculated as:

Options A and B are incomplete, while option C is an experimental method, not standard practice. The recognized method is option D.

Answer : D

LCC (Life Cycle Cost) is the metric that accounts for capital cost, operational energy, maintenance, and disposal/replacement. This holistic view is critical when evaluating cooling technologies like CRACs, CRAHs, chilled water, or free cooling systems.

HER (Heat Exchange Ratio) and COP (Coefficient of Performance) measure operational efficiency but not total lifecycle costs.

PUE measures overall data center efficiency but not specifically cooling CAPEX/OPEX.

Thus, LCC is the comprehensive metric that covers installation, operation, and disposal.

Answer : A

Battery sizing requires determining the real power demand of the UPS. With 30 kVA at 0.8 PF, the real load is 24 kW. To calculate required ampere-hours for 15 minutes of runtime, we need:

Where P = load, t = runtime, V = battery voltage, and = UPS efficiency.

Without UPS efficiency, we cannot know actual DC load on the batteries. A UPS with 90% efficiency will require more battery capacity than one with 95%. None of the other listed parameters (PF, imbalance, charging current) are critical for runtime capacity calculation.

Answer : B

Inert gas systems (e.g., Inergen, Argonite, Nitrogen) extinguish fire by reducing oxygen concentration, which typically requires reducing oxygen levels to ~12--15%. This means a very large volume of gas must be discharged into the room (up to 40--50% of the protected volume). Because inert gases have a low extinguishing effectiveness by weight, more total gas is required.

Halocarbon agents (FM-200, Novec 1230) extinguish fire chemically by interrupting the combustion chain reaction. They require only a small percentage (6--9%) concentration in the room volume. As a result, the storage space for cylinders is much smaller compared to inert gas systems.

Therefore, inert gas systems generally require a larger gas volume to achieve extinguishing concentrations.

Answer : C

ANSI/TIA-942 specifies minimum floor live load capacities based on Rated levels:

Rated-1/2: ~7.2--8.4 kPa

Rated-3: 12 kPa

Rated-4: 15 kPa

These values ensure raised floors can support racks, cabling trays, cooling units, and maintenance loads without structural compromise. For Rated-3, concurrent maintainability requires higher floor robustness to handle additional infrastructure.

Therefore, the correct requirement is 12 kPa.

Answer : B

Heat transfer occurs in three modes: conduction, convection, radiation. Conduction is transfer by direct contact of solids. Since the servers are touching metal-to-metal, heat flows directly from the warmer surface to the cooler one via conduction.

Radiation occurs without contact, across air or vacuum.

Convection requires a fluid medium like air, which is absent between surfaces.

''No heat transfer'' is incorrect---there will always be transfer.

Therefore, the unwanted transfer here is conduction.

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.