CDCS EXIN EPI Certified Data Centre Specialist Questions and Answers

Aerosol sprays release particulates and residues into the environment, which can contaminate sensitive ICT equipment. Such contamination accelerates corrosion, interferes with airflow, and increases particulate levels beyond ASHRAE recommended limits.

Proper cleaning should use HEPA-filtered vacuum systems or dry wipes, not aerosols. Even odor control aerosols are disallowed in critical rooms.

Therefore, aerosol cleaning solutions must never be used.

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:

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

Halocarbon agents such as FM-200 (HFC-227ea) and Novec-1230 (FK-5-1-12) are both defined under NFPA 2001 and ISO 14520 as clean agents, but their required design concentrations and physical properties differ. When calculating agent quantity, the minimum extinguishing concentration (MEC) and safety factor (S) must be taken into account. The S-factor is specific to each agent and reflects differences in molecular weight, density, and flame suppression chemistry.

For Novec-1230, the required design concentration is generally lower than for FM-200 (around 4.5–6% vs. 7–9%), but the calculation formula is the same except for substituting the correct S-factor. Therefore, you cannot reuse the exact formula parameters from FM-200; you must change the S-factor and apply Novec-1230’s physical constants.

This ensures compliance with NFPA 2001 Annex C, which provides correction formulas for room volume, temperature, and specific agent type. Using the wrong S-factor could result in underfilling or overfilling, compromising fire safety or increasing cost unnecessarily.

A hypoxic-based fire suppression system works by reducing the oxygen level in a room to below what is necessary to sustain combustion. This makes it effective in fire prevention, but it is not suitable for continuous occupancy by personnel. Low oxygen levels can cause discomfort or even health risks for people spending extended periods in the space. Therefore, these systems are typically deployed in areas where continuous human occupancy is not required, such as storage rooms or data halls with limited personnel access.

Detailed Explanation:

Hypoxic fire suppression systems lower oxygen levels to around 15-16%, which is safe for short periods but not sustainable for continuous occupancy without risk to health. Data center environments where staff need to spend long periods monitoring and maintaining equipment would need alternative systems, like gas-based suppression that allows for safe evacuation rather than oxygen reduction.

EPI Data Center Specialist References:

The EPI Data Center Specialist curriculum emphasizes that fire suppression systems must be chosen based on occupancy requirements. Hypoxic systems are specifically noted as unsuitable for spaces requiring continuous human presence due to the low oxygen environment they create.

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.

ASHRAE TC 9.9 recommends using dust deposition coupons (also called reactivity coupons) to measure particulate contamination over time. These are small, standardized metallic plates exposed to the air that collect dust and contaminants. After a set period, they are analyzed for chemical corrosion rates and particulate buildup.

Option A (handheld analyzers) gives spot counts of airborne particles but does not capture long-term corrosive deposition risk.

Option C only samples underfloor plenum dust, not actual IT environment contamination.

Option D (opening equipment) is invasive and risks voiding warranties.

Coupons provide standardized, passive, and reliable monitoring of contamination over months, making them the preferred method.

Earth Leakage Protection is primarily installed to protect human lives by detecting and disconnecting power when a fault current flows to the ground. This type of protection is essential to avoid electrical shock hazards that could occur when insulation fails, or equipment is improperly grounded.

Detailed Explanation:

Earth leakage currents can occur due to insulation faults or accidental contact with live parts. Earth Leakage Protection systems, such as Residual Current Devices (RCDs), quickly detect these faults and disconnect the circuit to prevent harm to personnel. This is especially crucial in environments like data centers where high-powered equipment is continuously running and any electrical fault can pose significant safety risks.

EPI Data Center Specialist References:

EPI emphasizes that human safety is paramount in data center operations. Proper grounding and leakage protection are fundamental safety measures, and EPI guidelines align with this focus, underscoring the importance of protecting personnel from electrical hazards through appropriate safety systems.

“Overcurrent” for protective devices is the condition above the device’s rated/trip value that causes operation (tripping/melting).

A = inrush tolerance, not the definition of overcurrent.

B = prospective short-circuit current (Ik).

The diagram shows three UPS modules, each 100 kW, connected in parallel to support a 100 kW IT load. That means:

One module (100 kW) can support the load (N).

Two additional modules are installed as redundancy.

This equals N+2 redundancy.

2+N+1 and 2(N+1) imply dual active paths not shown.

N+N+N is not an industry term.

Thus, the correct redundancy level is N+2.

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 References:

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.

Given the customer’s requirement to limit Total Harmonic Distortion (THDi) to below 3% and the presence of a 6-pulse SCR/Thyristor-based rectifier, an active harmonic filter is the best solution. A 6-pulse rectifier typically generates higher harmonic distortion, often exceeding 3%, especially under substantial loads like 80%. An active harmonic filter dynamically monitors and compensates for harmonic distortion, effectively reducing THDi and supporting a more power-efficient operation, aligning with the customer’s energy efficiency goals.

Detailed Explanation:

Passive harmonic filters can reduce harmonics but are less effective at maintaining low THDi levels under varying loads. Active filters offer real-time correction and can achieve lower THDi levels than passive filters, especially in systems with fluctuating loads or where strict harmonic limits are required. Installing an active harmonic filter will ensure compliance with the specified THDi limits and optimize power quality.

EPI Data Center Specialist References:

EPI guidance on power quality management recommends active harmonic filters for environments where strict THDi levels are necessary. Active filters offer better control over harmonic levels, supporting both compliance and operational efficiency.

The server’s repeated overheating despite adequate intake and exhaust temperatures suggests that dust buildup inside the server may be impeding heat transfer. Dust accumulation can obstruct airflow within the server, insulate components, and disrupt the convection-based cooling systems that regulate internal temperatures, leading to overheating and potential hardware failures.

Detailed Explanation:

While the intake and exhaust temperatures appear within acceptable ranges, internal dust can reduce airflow and impede cooling efficiency, causing internal components to overheat despite seemingly normal ambient conditions. Regular cleaning and maintenance are critical for preventing dust-related issues, especially in high-powered equipment like a 5kW server.

EPI Data Center Specialist References:

EPI emphasizes regular maintenance to prevent dust buildup in data center equipment. Dust can significantly impact cooling efficiency and lead to overheating, which underlines the importance of routine cleaning for optimal server performance.

A Power Usage Effectiveness (PUE) of 1.20 (achieved by Data Center B) indicates the highest facility efficiency among the three data centers. A lower PUE value signifies better energy efficiency, as it means that a greater proportion of the total energy consumed is used directly for IT equipment rather than for cooling, lighting, or other facility needs.

Detailed Explanation:

PUE is calculated as the ratio of total facility energy to IT equipment energy. A PUE close to 1.0 suggests that almost all the energy is dedicated to computing processes, with minimal overhead. With PUE values of 2.45, 1.20, and 1.90, Data Center B (1.20) operates most efficiently by devoting a higher percentage of its total energy to IT equipment.

EPI Data Center Specialist References:

The EPI curriculum emphasizes PUE as a key metric for data center efficiency, with lower values representing better performance. Achieving a PUE near 1.0 aligns with industry best practices for energy-efficient data center design and operation.

When installing an automated lighting system, especially in a security-sensitive area like a data center, it’s essential to ensure that lighting levels support security camera functionality at all times. Sufficient lighting is necessary for cameras to capture clear footage, ensuring continuous monitoring and security regardless of occupancy.

Detailed Explanation:

Automated lighting based on occupancy or time settings can reduce energy costs, but it must be configured to maintain adequate illumination for surveillance. Security cameras require minimum lighting levels to operate effectively, so lighting should be configured to avoid compromising security.

EPI Data Center Specialist References:

EPI emphasizes security and safety in data centers, advising that lighting systems should maintain levels conducive to effective surveillance, ensuring operational security even when lights are automatically controlled.

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.

The data center life cycle is typically divided into four stages:

Design (scope, architecture, planning)

Implement (construction, installation, testing & commissioning)

Operate/Optimize (day-to-day operations, maintenance, continuous improvement)

Retire (decommissioning and migration)

Testing and commissioning occur in the Implement stage, after construction but before handover. This includes Integrated Systems Testing (IST), which validates that all systems (electrical, cooling, fire protection, telecom) perform to design intent and redundancy requirements.

Without commissioning, the data center cannot be certified or considered operational.

When the window area exceeds the maximum exposed area specified for fire-rated glass, it is necessary to split the window into sections that comply with the fire rating requirements. This means creating smaller sections that are each within the 3 sqm/32 sqft limit and using fire-rated frames to ensure that the entire assembly meets fire safety standards. This approach maintains the fire-rated integrity of the glass, while allowing for larger window areas.

Detailed Explanation:

Fire-rated glass is designed to contain fire and prevent it from spreading. If the window exceeds the maximum exposed area defined by the supplier, the integrity of the fire-rated glass could be compromised. By dividing the window into compliant sections with fire-rated frames, you ensure that each pane performs as intended in the event of a fire. Fire-rated frames help maintain the fire resistance across the entire assembly, making this option the best for safety and compliance.

EPI Data Center Specialist References:

EPI recommends adhering strictly to fire safety standards, especially when using materials like fire-rated glass. The guidelines emphasize that modifications should always respect the manufacturer’s specifications to ensure the system remains effective in containing and preventing the spread of fire.

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.

In locations with consistently cold temperatures, such as above the Arctic Circle, an airside economizer is the most energy-efficient cooling solution. Airside economizers use cool outside air to lower indoor temperatures, reducing or even eliminating the need for mechanical cooling. Given the consistently low temperatures, this method maximizes energy efficiency by leveraging natural cooling.

Detailed Explanation:

Airside economizers are ideal in environments where outside temperatures are consistently low. By drawing in and filtering cold outdoor air, they directly cool the indoor environment, thereby reducing energy consumption significantly compared to traditional air conditioning. This cooling approach aligns with energy efficiency goals by minimizing mechanical cooling demands.

EPI Data Center Specialist References:

EPI recommends the use of airside economizers in cold climates to achieve high energy efficiency, as they allow data centers to capitalize on ambient conditions for cooling, aligning with sustainability and cost-saving practices.

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.

ANSI/TIA-942 defines that the lowest rating across all four categories determines the overall facility rating. A facility cannot claim a higher overall level unless all subsystems meet or exceed that level.

In this case:

Mechanical = Rated-3

Electrical = Rated-4

Telecommunications = Rated-2

Since telecommunications only meets Rated-2, the overall facility is Rated-2, regardless of higher scores elsewhere.

This ensures that weak areas (like cabling) are not ignored, because they can compromise overall availability.

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.

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.

For optimal early smoke detection in a data center, it is crucial that the Very Early Smoke Detection Apparatus (VESDA) system be installed at locations where smoke will be detected as soon as it appears. Positioning the VESDA pipes at the air intake of the air conditioner inside the computer room is not ideal. This placement could result in a delayed detection response and the potential for bypass airflow to occur, which would impede the system’s ability to detect smoke effectively.

Detailed Explanation:

When VESDA pipes are installed at the air intake, the detection system relies on the smoke to be drawn into the air conditioning unit before detection can occur. This setup increases the reaction time as the smoke has to travel through the intake and get processed by the air conditioner. Furthermore, bypass airflow—a phenomenon where not all the air containing smoke particles passes through the VESDA pipes—could also delay or even prevent the system from detecting smoke early.

Ideally, VESDA pipes should be positioned where smoke is likely to accumulate first, such as near the ceiling or in the return airflow path to detect smoke at the earliest possible stage. This ensures that the detection system can quickly trigger alarms, providing more time to address potential fire hazards.

EPI Data Center Specialist References:

EPI Data Center Specialist training highlights that smoke detection should prioritize early response capabilities to maximize safety. The preferred installation for VESDA pipes is generally at points where smoke would naturally accumulate, rather than relying on air conditioning intakes where airflow can vary and delay detection. In their course materials, EPI emphasizes minimizing reaction time and reducing the impact of airflow dynamics on smoke detection efficiency.

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.

Inert gas systems (Inergen, Argonite, Nitrogen) extinguish fires by reducing oxygen concentration through massive gas discharge. This rapid release causes a significant pressure rise inside the room. To avoid structural damage to walls, ceilings, or raised floors, pressure relief vents (pressure release valves) must be installed.

A (drainage) applies to water suppression.

B (tank location) is logistical but not mandatory; remote storage with piping is acceptable.

D (water leak detection) is unrelated to inert gas suppression.

Therefore, the critical safety requirement is pressure relief.

Perforated tiles with integrated dampers are common in raised-floor data centers because they allow airflow regulation at the rack level. However, even when the damper is fully open, the mechanism inside the tile restricts airflow. This typically reduces the delivered airflow by around 10% compared to a non-dampered tile of the same type.

Option A is incorrect because dampers do not affect supply temperature; they only throttle volume.

Option B is wrong since dampers cannot increase volume—they only add resistance.

Option D is partially true that dampers help with temperature balancing, but the main effect (in open position) is volume reduction.

Thus, the technical impact of dampers in open position is a slight airflow reduction, usually quantified as ~10%.

The formula used to calculate the gas content differs significantly between halocarbon and inert-based fire suppression systems. Halocarbon systems function by absorbing heat, while inert systems work by reducing oxygen levels. Due to these differences in fire suppression mechanisms, distinct formulas are applied, factoring in the specific properties of each gas type and the required concentration levels.

Detailed Explanation:

Halocarbon systems like FM200 require a formula that accounts for the concentration needed for cooling, while inert gases like nitrogen or argon need a formula that calculates the volume based on oxygen displacement. As the design concentration and characteristics of these gases differ, it’s essential to use the correct formula specific to the gas type.

EPI Data Center Specialist References:

EPI recommends consulting the specific design requirements and formulas provided by each gas manufacturer when switching fire suppression systems to ensure the correct amount of gas is deployed for effective fire suppression.

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 References:

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

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.

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.

ANSI/TIA-942 requires a risk assessment–based approach to physical security; ballistic protection is not mandated but may be justified by threat analysis.

A is incomplete (it may still be required by risk).

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.