CDCS EXIN EPI Certified Data Centre Specialist Questions and Answers

OM5 is optimized for Short Wavelength Division Multiplexing (SWDM) between 850–953 nm. This allows transmission of multiple wavelengths over a single fiber pair, reducing the number of fibers required for high-speed links.

OM4 already supports 100 GbE to 150 m, but OM5 with SWDM extends reach and reduces cabling bulk.

Option B is false because OM5 offers distinct SWDM benefits.

Option C is incorrect—OM5 is laser-optimized, not LED-based.

Option D is misleading; OM5 doesn’t extend 100 GbE to 500 m (that requires single-mode OS2 fiber).

Thus, the key advantage is SWDM support.

To determine the required capacity of the battery bank for the 15-minute runtime at full load, one must know the total power requirement that the battery bank must supply. The specifications provided include most of the necessary details, such as rated power, input voltage, battery voltage, and discharge voltage. However, one critical piece of information is missing: the UPS efficiency.

Detailed Explanation:

In a data center UPS system, the battery bank is designed to supply power for a set duration when there is an input power failure. The UPS efficiency affects the actual power the UPS can deliver to the load compared to the power it draws from the batteries. The efficiency factor is necessary to accurately calculate the required capacity of the battery bank since it determines how much input power is needed from the batteries to supply the load at full capacity. The formula typically used to determine battery capacity involves factoring in UPS efficiency, as it allows you to understand the losses within the UPS system.

If UPS efficiency is not considered, there would be an inaccurate estimation of the actual power needed from the batteries. For instance, if a UPS has 90% efficiency, only 90% of the power drawn from the batteries reaches the load. Without knowing this efficiency, it is not possible to calculate the battery bank size accurately, as you cannot accurately estimate the losses within the UPS itself.

EPI Data Center Specialist References:

According to EPI Data Center Specialist training, understanding the UPS efficiency is essential for battery sizing. Without it, the calculations could lead to either undersizing or oversizing the battery bank, which affects both reliability and cost-effectiveness of the UPS system. The EPI Data Center Specialist course emphasizes that battery sizing must account for all losses within the UPS system, with efficiency being a primary factor in these calculations.

High levels of H2S (hydrogen sulfide) gas contamination in a computer room are best addressed by installing air-scrubbers. Air-scrubbers can effectively filter out contaminants, including corrosive gases like H2S, ensuring clean air circulation and protecting sensitive IT equipment from potential corrosion and damage.

Detailed Explanation:

Air-scrubbers are designed to remove various airborne contaminants and are particularly useful in environments where corrosive gases are present. These systems use filters or chemical reactions to neutralize harmful substances, making them ideal for data centers that need to maintain high air quality for equipment reliability.

EPI Data Center Specialist References:

EPI guidelines suggest air-scrubbing technologies to remove contaminants that pose risks to electronic equipment, maintaining air quality and reducing corrosion risk.

The diagram shows two independent utility feeds, each backed up by generators, connected to two separate distribution paths. Each path supplies its own UPS system in an N+1 configuration, which then feeds PDUs and ICT loads. Mechanical equipment also has dual redundant feeds. This means the electrical design ensures concurrent maintainability (systems can be maintained without downtime) and fault tolerance (a single fault anywhere in the power path will not impact ICT load).

According to ANSI/TIA-942-B, the electrical infrastructure for a Rated-4 data center must have two active distribution paths, each independently capable of supporting the ICT load. It also requires full redundancy (N+1 or greater) on critical components such as UPS and generators. This diagram clearly illustrates that architecture: dual feeds, dual UPS, and fault tolerance.

In contrast, Rating-3 offers concurrent maintainability but does not guarantee full fault tolerance. Rating-2 and Rating-1 are less stringent and would not provide the dual power distribution seen here.

An imbalance in load sharing between UPS systems connected in parallel can often result from unequal cable lengths to the common busbar. If the cabling from each UPS to the busbar varies significantly in length, it can lead to differences in impedance, resulting in uneven load distribution. Ensuring that cable lengths are consistent helps to balance the load sharing across the UPS systems.

Detailed Explanation:

Parallel UPS systems rely on uniform impedance to share loads evenly. Differences in cable lengths cause variations in resistance, leading to one or more UPS units carrying a disproportionate share of the load. Standardizing cable lengths ensures equal impedance, which promotes balanced load sharing and prevents one UPS from being overburdened, thus maintaining overall system reliability.

EPI Data Center Specialist References:

EPI guidelines recommend checking cable lengths when load imbalances occur in parallel UPS configurations. Ensuring equal lengths is a common method to resolve impedance issues that affect load distribution, which is critical for the stable operation of redundant power systems.

EoR centralizes access/aggregation switches at the end of each row, reducing the number of access switches compared with ToR (one per rack), which simplifies management and often lowers Ops costs.

A, D are incorrect generalizations.

For a Rated-3 data center, network architecture is indeed a key component of the audit under ANSI/TIA-942. This rating requires concurrent maintainability across all systems, including telecommunications infrastructure. The network architecture must therefore meet specific redundancy and reliability standards to ensure uninterrupted operations during maintenance or failure of any single component.

Detailed Explanation:

Rated-3 requirements extend beyond electrical and mechanical systems to include network architecture. This ensures that telecommunications systems are also designed for concurrent maintainability, thus contributing to overall uptime and resilience.

EPI Data Center Specialist References:

EPI endorses comprehensive assessments for Rated-3 facilities, emphasizing that network systems must meet standards for redundancy and concurrent maintainability, which align with ANSI/TIA-942’s holistic approach to data center reliability.

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 η = 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.

Hydrogen sulfide (H₂S) is a corrosive gas that readily reacts with metals, especially copper and silver found in circuit boards, connectors, and power supply components. Even at concentrations below human detection thresholds, H₂S can cause sulfidation corrosion leading to intermittent connections, failure of solder joints, and increased failure rates of electronic equipment.

ASHRAE Technical Committee 9.9 has documented multiple failures in data centers due to corrosive gases (notably sulfur-bearing compounds). Therefore, high humidity combined with H₂S presence accelerates this risk.

H₂S does not affect static flooring properties (B) or fire suppression agent chemistry (D). Option A is clearly incorrect as the risk is well-documented.

When installing overhead data cabling, it’s crucial to maintain minimum separation from power cables to prevent electromagnetic interference. Additionally, cabling should be arranged so that it does not obstruct fire detection and suppression systems, allowing for proper sensor function and suppression agent dispersion in the event of a fire.

Detailed Explanation:

Separation between power and data cabling minimizes the risk of interference and helps ensure compliance with standards for signal integrity. Proper placement relative to fire suppression systems ensures that any smoke or heat can be effectively detected, and suppression agents can be evenly distributed without obstruction from cabling.

EPI Data Center Specialist References:

EPI guidelines emphasize maintaining adequate separation between power and data cables for safety and performance and ensuring cabling does not interfere with essential safety systems in data centers.

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

Charging Current=800Ah×0.1=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 References:

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.

When installing a raised floor, the best starting point is typically from the farthest corner away from the entrance, in this case, Point B. This method allows for the floor installation to progress towards the entrance, ensuring that workers can avoid walking over the newly installed tiles, thus minimizing the risk of damage and maintaining cleanliness during installation.

Detailed Explanation:

Starting at the farthest corner (Point B) and working towards the entrance (Point A) is a standard practice in raised floor installation. This approach ensures that installers do not walk over freshly laid tiles, which could lead to shifting or misalignment. Additionally, it allows for more controlled placement and alignment, as well as convenient egress when installation is complete.

EPI Data Center Specialist References:

EPI guidelines for raised floor installation emphasize beginning at the farthest point from the entrance and working back towards it, which aligns with industry best practices for efficiency and quality assurance. This method reduces potential damage and supports precise alignment across the floor area.

ASHRAE recommends temperature and humidity be measured in the cold aisle, in front of racks, at approximately 1.5 m above the floor (average human working height) and 0.3–0.5 m from the rack face. This location captures the environmental conditions experienced at the IT equipment air intake, while still representing facility-level conditions (not single device-level).

Option A and C (at 50 mm intake/rear) are too close to individual servers and suited only for rack-level monitoring, not facility monitoring.

Option D (rear measurement) reflects exhaust air, not intake, and thus cannot be used to control environmental setpoints.

Maintaining measurement at standardized facility locations allows comparisons against ASHRAE’s recommended and allowable ranges (18–27 °C for Class A1 environments, 40–60% RH).

EMF shielding is most effective when installed close to the source of the EMF, which in this case is the transformer room. Shielding at the source contains the magnetic fields before they spread, minimizing exposure throughout the facility, including the computer room.

Detailed Explanation:

Placing shielding close to the EMF source minimizes the area impacted by electromagnetic interference, as it reduces the distance over which the EMF can spread. Shielding materials near the source can absorb or redirect EMF, providing the most effective reduction of EMF levels in adjacent spaces, like the data center.

EPI Data Center Specialist References:

EPI data center training advises positioning shielding close to the EMF source to contain fields more effectively and reduce interference in critical areas. This method is more efficient and cost-effective, as it limits the spread of EMF from the point of origin.

High relative humidity (above 80%) creates a serious risk for corrosion of electronic contacts, printed circuit boards (PCBs), and metallic components. Moisture in the air condenses more easily, especially when surfaces are cooler than ambient dew point. This can lead to oxidation of connectors, degradation of solder joints, and eventual failures in ICT hardware.

Electrostatic discharge (ESD) risks, by contrast, increase at low humidity (below 30%) because dry air promotes charge buildup. Therefore, option C is incorrect here. Similarly, option D (cooling risk from wet-bulb temperature) applies to evaporative cooling efficiency, not directly to ICT risk.

ASHRAE recommends data centers maintain RH between 40–60% for optimal reliability. Values above 80% RH are considered outside the recommended operating envelope and significantly increase the risk of corrosion, especially in the presence of airborne contaminants like sulfur dioxide (SO₂) or hydrogen sulfide (H₂S).

Therefore, the verified risk at 85% RH is corrosion-related degradation.

The Open Compute Project (OCP), initiated by Facebook in 2011, focuses on open designs for servers, storage, racks, and power systems. The goals are:

Reduce energy consumption by using efficient hardware.

Save materials by eliminating unnecessary components.

Lower costs by standardizing and sharing open designs.

Option B is wrong—OCP hardware can be adopted by enterprises as well. Option C is unrelated (OCP is hardware, not OS). Option D is broader cloud adoption, not OCP’s direct mission.

Thus, the primary focus is energy, material, and cost savings through open-source hardware.

For a cooling audit in a data center, it is essential to measure temperature and humidity where air enters the servers to accurately assess cooling performance. In this case, since all servers have a front-to-rear (F-R) airflow design, measuring at the front/intake of the server will provide a precise understanding of the cooling conditions that the equipment is experiencing.

Detailed Explanation:

Servers with a front-to-rear airflow design draw in cool air from the cold aisle at the front, which is then exhausted into the hot aisle at the rear. By measuring temperature and humidity 50 mm/2 inches from the front intake, you gather data on the air conditions right before it enters the servers, providing an accurate representation of the cooling environment as it directly impacts the equipment.

Measuring in the cold aisle at the front intake ensures that the readings reflect the actual conditions of the incoming air that the servers depend on for effective cooling. This approach is consistent with best practices for maintaining thermal conditions in a data center, as it helps confirm that the cooling systems are delivering air within the required temperature and humidity specifications.

EPI Data Center Specialist References:

According to the EPI Data Center Specialist curriculum, the optimal placement for temperature and humidity sensors is at the intake of the equipment in the cold aisle, as it directly correlates to the environmental conditions affecting the servers. This positioning allows for a more effective audit of cooling performance, which is critical for maintaining the reliability and efficiency of the data center’s operations.

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.

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.

Hypoxic air systems continuously reduce the oxygen concentration in the protected area to below the level required for combustion (typically 15–16%), while still remaining safe for human occupancy (>14%). By lowering oxygen concentration, ignition and flame propagation are prevented.

This is different from halocarbon or inert-gas clean agents, which flood the room only upon detection of fire. Hypoxic systems are preventive, creating a permanent fire-retardant environment.

They do not remove heat (A), fuel (C), or use water (D). Their key mechanism is oxygen displacement.

High dust levels in a computer room are often due to improperly fitted floorboards. When floorboards are not securely installed or do not fit tightly, they allow dust and particles from the subfloor to enter the room. In a data center, this can lead to high levels of dust that affect air quality and equipment performance.

Detailed Explanation:

Raised floors in data centers can accumulate dust and debris, especially if the floorboards are not properly sealed. Loose or improperly fitted floorboards allow contaminants from the subfloor to enter the data center environment, increasing the dust levels over time. Proper installation and maintenance of floor panels are essential to prevent dust infiltration and maintain clean conditions.

EPI Data Center Specialist References:

EPI training emphasizes proper flooring installation and maintenance to control air quality within data centers. Correctly fitted floorboards prevent dust accumulation from the subfloor, which helps protect sensitive equipment and maintains a cleaner environment.

Choosing pre-terminated category 6 or 6A cabling provides several advantages, primarily related to time savings and reliability. Since pre-terminated cables are factory tested, they ensure consistent quality and performance, reducing the need for additional testing during installation. This makes installation faster and more efficient, which can significantly reduce labor costs and deployment times.

Detailed Explanation:

Pre-terminated cabling systems are manufactured and tested in controlled environments, which ensures they meet industry standards for performance. This factory testing process minimizes the likelihood of faults, reducing the need for troubleshooting and retesting on-site. Moreover, pre-terminated solutions can help to streamline installations because they eliminate the need for on-site terminations, which can be time-consuming and require skilled labor.

This is especially beneficial for data centers, where rapid deployment and minimizing potential points of failure are critical to maintaining uptime. However, it is important to note that pre-terminated cables require accurate planning, as lengths and connector configurations must be predetermined.

EPI Data Center Specialist References:

According to EPI Data Center Specialist guidelines, pre-terminated cabling is advantageous in data center environments due to reduced installation time and enhanced reliability from factory testing. These attributes align with best practices for efficient data center management, where maintaining performance and minimizing downtime are priorities.

Best practice is to begin raised-floor installation at the center of the room, working outward. This minimizes alignment errors and ensures the tile grid is centered, which is critical for aisle containment and rack alignment.

Starting at the perimeter (A, B, D) causes cutting of tiles along both sides, misalignment with rack rows, and possible airflow inefficiencies. By starting at the center, tiles can be cut symmetrically around the edges, providing better aesthetics, balanced airflow, and structural stability.

Industry guidelines such as CISCA recommend this approach for raised floors in mission-critical spaces.

SHR = Sensible Load / (Sensible + Latent Load); it describes the portion of the total cooling that is sensible (temperature change) versus latent (moisture removal).

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.

As relative humidity decreases, Electrostatic Discharge (ESD) risks increase. Lower humidity levels reduce the amount of moisture in the air, which normally helps dissipate static charges. When the humidity drops from 50% to 35%, the likelihood of static electricity accumulating on surfaces rises, leading to a higher potential for ESD incidents that could damage sensitive IT equipment.

Detailed Explanation:

ESD events are more common in dry environments because there is less atmospheric moisture to neutralize electrical charges. Maintaining relative humidity above 40% helps minimize the risk of ESD, which is why data centers often control humidity levels tightly to protect equipment from static discharge that could cause hardware failures or data loss.

EPI Data Center Specialist References:

EPI data center best practices stress the importance of maintaining stable humidity levels to prevent ESD, particularly in computer rooms. Recommended humidity ranges are typically above 40% to prevent conditions that would foster static buildup.

To calculate the cooling airflow requirement for ICT equipment, you can use the formula:

CFM=Power (kW)×3160ΔT(°F)\text{CFM} = \frac{\text{Power (kW)} \times 3160}{\Delta T (\text{°F})}CFM=ΔT(°F)Power (kW)×3160​

For equipment consuming 6 kW with a Delta-T of 20°F:

CFM=6×316020=948≈1,000 CFM\text{CFM} = \frac{6 \times 3160}{20} = 948 \approx 1,000 \, \text{CFM}CFM=206×3160​=948≈1,000CFM

Detailed Explanation:

This formula provides an estimate of the cubic feet per minute (CFM) of air required to cool the equipment based on its power consumption and the temperature difference (Delta-T) between intake and exhaust. The Delta-T represents the cooling effectiveness of the airflow.

EPI Data Center Specialist References:

EPI recommends using this calculation for determining airflow requirements in data centers, ensuring that cooling systems are adequately sized to maintain equipment within safe temperature limits.

For an MCB (Miniature Circuit Breaker) in the PDU of an air-conditioning unit, a C-Curve is recommended. C-Curve breakers are suitable for circuits with moderate inrush currents, such as those experienced in air conditioning units. They provide protection against overloads while accommodating the inrush without nuisance tripping.

Detailed Explanation:

C-Curve breakers trip when currents exceed 5 to 10 times the rated current, making them ideal for devices like air conditioners that experience moderate inrush currents upon startup. This characteristic provides a balance between protection and resilience against startup surges, preventing unnecessary trips while safeguarding the circuit.

EPI Data Center Specialist References:

EPI guidance for data center electrical systems specifies that C-Curve breakers are appropriate for equipment with inrush characteristics similar to air conditioning units, as they help prevent operational interruptions caused by typical surges during equipment start-up.

PUE (Power Usage Effectiveness) is the most widely used metric to evaluate the energy efficiency of data centers. Defined by The Green Grid and adopted in ISO/IEC 30134-2, PUE is the ratio of the total facility power to the ICT (IT load) power.

Formula:

Total Facility Power includes all electrical consumption: IT, cooling, lighting, power distribution losses, UPS inefficiency, etc.

ICT Equipment Power is only the load drawn by servers, storage, and networking gear.

An ideal PUE is 1.0, meaning all power is used by ICT equipment with no overhead. Typical enterprise values are 1.5–2.0, while hyperscale operators target <1.2.

Other options are incorrect:

B represents the inverse metric, known as DCiE (Data Center infrastructure Efficiency).

C and D are partial subsystem efficiency metrics, not the global PUE.

Attenuation is the logarithmic ratio between input and output signals. For power, we use 10 log; for voltage or current, 20 log. Since EMF shielding is measured as field strength (V/m or A/m), power relationship is proportional to the square of field. Thus the correct attenuation calculation for shielding effectiveness is:

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where:

M = maximum permissible field strength

R = measured field strength after shielding

This ensures the shield reduces field intensity to below allowable limits.

MPO (Multi-fiber Push On) pre-terminated fiber offers the advantage of quick installation and supports high-speed upgrades up to 40 Gbit/s and 100 Gbit/s. This technology simplifies connections by allowing multiple fibers to be connected in a single plug-and-play module, reducing installation time and making future expansions or upgrades to higher speeds easier.

Detailed Explanation:

MPO connectors consolidate multiple fiber connections into a single interface, which simplifies cable management and reduces installation complexity. This setup is particularly beneficial in data centers where high-speed networks are essential, and where rapid deployment is necessary. MPO pre-terminated fiber also supports the use of OM4 fiber, making it compatible with existing high-performance cabling infrastructure.

EPI Data Center Specialist References:

EPI training highlights that pre-terminated fiber solutions, like MPO, can greatly enhance efficiency in data centers. By reducing installation time and providing scalability for higher transmission speeds, they align with best practices for maintaining flexible and future-ready network infrastructure.

In computer rooms, replacing a wet pipe system with a pre-action system is advisable. Pre-action systems provide additional protection by requiring two triggers (e.g., heat and smoke) before water is released, minimizing the risk of accidental discharge and water damage, which is crucial for safeguarding sensitive IT equipment.

Detailed Explanation:

Wet pipe systems contain water in the pipes at all times, which poses a higher risk of accidental discharge. Pre-action systems, however, only fill the pipes with water upon detection of a fire, reducing the risk of water-related damage due to leaks or malfunctions. This approach is considered best practice for environments housing sensitive electronic equipment.

EPI Data Center Specialist References:

EPI advises using pre-action fire suppression in data centers to reduce risks associated with accidental water release, providing a safer and more controlled fire response that better protects critical infrastructure.