CDCS EXIN EPI Certified Data Centre Specialist Questions and Answers

The electrical design shown in the diagrams represents aTIA-942 Rating-4configuration. This design includesfull redundancy and fault tolerance, as demonstrated by the dual power distribution paths from the utility supply to the critical loads. Each power distribution path isequipped with its own UPS, ensuring that the ICT equipment and mechanical equipment have uninterrupted power in case of any single point of failure.

Detailed Explanation:

ARating-4data center requires two independent power paths that are fully redundant and capable of supporting the load independently. In the diagrams:

There are dual feeds from the utility supply, each going through separate transfer switches and power distribution paths.

Both paths have backup sources (+1) and serve critical components through separate UPS systems, providing a completely redundant setup.

The design also includes redundant paths to the mechanical equipment and ICT equipment, which further indicates the fault-tolerant characteristics of a Rating-4 infrastructure.

This setup allows for concurrent maintainability and ensures that no single failure in power distribution or UPS can impact the data center’s operation, which is characteristic of the highest Tier/Rated-4 classification.

EPI Data Center Specialist References:

EPI guidelines confirm that TIA-942 Rating-4 requires full redundancy and fault tolerance for electrical infrastructure, ensuring continuous operation even during maintenance or failure events. This design meets all those requirements, thus aligning with Rating-4 standards.

Thecooling capacity of a raised floor tileis primarily influenced by thepercentage of surface opening, theobstruction caused by the supporting construction, thepressure under the raised floor, and thedamper construction. These factors dictate how much airflow can pass through the tile and how effectively cool air is distributed to the equipment in the data center.

Detailed Explanation:

Thepercentage of surface openingon a floor tile affects how much air can flow through, with larger openings allowing more airflow.Supporting structuresbeneath the floor can obstruct airflow, reducing cooling efficiency.Pressure under the raised floorimpacts the velocity and volume of air that moves through the tile. Additionally, ifdampersare installed, they control the airflow rate, which can be adjusted to meet specific cooling needs for the area.

EPI Data Center Specialist References:

EPI guidance on airflow management under raised floors emphasizes these factors as critical for effective cooling, especially in high-density areas. Ensuring unobstructed and adequate airflow helps maintain consistent cooling across equipment.

Anair intake temperature of 25 °C (77 °F)at thetop of the rackisacceptableaccording to data center standards and guidelines, such as those fromASHRAE. This temperature falls within the recommended range for inlet temperatures, which is typically between 18°C (64°F) and 27°C (81°F).

Detailed Explanation:

ASHRAE standards provide guidelines on acceptable temperature ranges for air intake in data centers to balance cooling efficiency and equipment safety. A temperature of 25°C is within the recommended operational range, allowing data centers to optimize energy efficiency while maintaining safe conditions for IT equipment.

EPI Data Center Specialist References:

EPI guidelines align with ASHRAE recommendations for server intake temperatures, confirming that 25°C is within acceptable limits for most mission-critical equipment. This ensures the data center maintains an efficient and reliable environment.

In ahot/cold aisle configuration, placingdown-flow air conditioners perpendicular to the cold aisleensures that cool air is directed efficiently into the cold aisles where server intakes are located. This layout allows for optimal cooling performance by aligning the airflow directly with the equipment intakes, minimizing hot spots and enhancing cooling efficiency.

Detailed Explanation:

With a raised floor design, cold air from the air conditioners is supplied into the cold aisle, where server intakes are located. Positioning the air conditioning units perpendicular to the cold aisles ensures that cool air is delivered directly into these aisles, preventing air mixing and optimizing cooling. This setup takes full advantage of the airflow management strategy inherent to the hot/cold aisle configuration.

EPI Data Center Specialist References:

EPI guidelines on cooling emphasize that down-flow air conditioners should be positioned to maximize the effectiveness of cold aisle delivery, which improves cooling efficiency and helps maintain consistent temperatures across server racks.

The design and configuration of racks, particularlyhigh-density and closed-circuit cooling racks, directly impact thefire suppression systemdesign. Closed-circuit cooling racks, like blade-center racks, can affect airflow and potentially trap heat, influencing how fire suppression agents are distributed within the space. Therefore, it is essential to inform the fire suppression system supplier about the rack design to ensure effective coverage and proper agent distribution.

Detailed Explanation:

High-density racks can change how smoke and heat travel, which in turn affects fire detection and suppression. Closed racks with built-in cooling can isolate airflow, requiring adjustments in fire suppression design to ensure that suppression agents reach all necessary areas, including within enclosed spaces. The supplier may need to account for these factors to ensure proper protection coverage.

EPI Data Center Specialist References:

The EPI Data Center Specialist training underscores that fire suppression systems must be tailored to the specific environmental characteristics of the data center. The design of racks, particularly high-density configurations, should always be considered to ensure that suppression agents can effectively control a fire, even in contained rack spaces.

In locations with consistentlycold temperatures, such asabove the Arctic Circle, anairside economizeris 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.

A potential disadvantage of using awater mist fire suppression systemis that it canrapidly increase the humiditywithin the data center, which may pose risks tosensitive electronic equipment. Excessive humidity can lead to condensation, which could damage electronics and leadto short circuits or corrosion over time.

Detailed Explanation:

Water mist systems use fine droplets to suppress fires by cooling and displacing heat. However, the moisture generated may raise the humidity level to the point where it exceeds safe operational limits for IT equipment. Therefore, while water mist systems are effective in fire suppression, they may not be ideal in environments where high humidity could damage sensitive equipment.

EPI Data Center Specialist References:

EPI guidelines advise considering the impact of humidity from fire suppression systems, particularly in environments housing electronic equipment. It’s essential to weigh the benefits of fire suppression against potential risks to operational equipment when choosing suppression methods.

WithHalocarbon fire suppression systems, as thetemperature increases, the amount of gas required for effective suppressiondecreases. This is because Halocarbon agents are stored as a liquid and discharge as a gas, expanding more at higher temperatures. As a result, less agent is needed at higher room temperatures to achieve the desired concentration for fire suppression.

Detailed Explanation:

Halocarbons rely on specific volumetric concentrations to suppress fires. Higher temperatures cause the agent to expand more rapidly, effectively filling the protected area with less agent needed to reach the required concentration. This is in contrast to some other gases, where temperature changes might not have the same effect on discharge quantities.

EPI Data Center Specialist References:

EPI data center training on fire suppression indicates that understanding the physical properties of agents like Halocarbons is key for correct system sizing. As the temperature rises, the gas expands more readily, thus requiring adjustments in the amount needed for effective coverage.

Given the customer’s requirement to limitTotal Harmonic Distortion (THDi) to below 3%and the presence of a6-pulse SCR/Thyristor-based rectifier, anactive harmonic filteris 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 morepower-efficientoperation, 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.

From anefficiency standpoint,Unit Bwith aSensible Heat Ratio (SHR) of 0.9is preferable. A higher SHR indicates that a greater proportion of the air conditioner's capacity is dedicated tosensible cooling(temperature reduction) rather thanlatent 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 datacenters, 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.

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 theair intake of the air conditionerinside the computer room isnot ideal. This placement could result in adelayed detectionresponse and the potential forbypass airflowto 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.

For aRated-3 data center,network architectureis indeed a key component of the audit underANSI/TIA-942. This rating requiresconcurrent maintainabilityacross 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.

A2(N+1) configurationimpliestwo independent UPS systems, each withN+1 redundancy. This configuration provides high availability by ensuring that each UPS system can independently support the load with an additional unit for redundancy. Given the80 kW load, this setup impliesthat two separate N+1 systems are running, providing reliability and fault tolerance for the data center’s power needs.

Detailed Explanation:

TheN+1notation denotes that each system has one additional unit beyond what is needed to carry the load, providing redundancy. With2(N+1), there are two such setups, ensuring that if one fails, the other can still support the load without interruption, fulfilling high availability requirements.

EPI Data Center Specialist References:

EPI teaches that multiple redundant systems, such as2(N+1), enhance data center reliability by ensuring that power is maintained even if a failure occurs in one system. This meets the stringent demands for uptime in critical environments.

AnEnd of Row (EoR) designminimizes the number of network switches, as multiple racks can share a single switch at the end of a row, reducing switch counts and simplifying management. Thisdesign centralizes network switching to fewer points, which reduces the complexity and number of switches required compared to a Top of Rack (ToR) design, where each rack typically has its own switch.

Detailed Explanation:

In EoR designs, each row has a single network switch that handles the connections for all racks within that row. This reduces the number of individual switches needed and centralizes network management, which is ideal for minimizing equipment and simplifying infrastructure in the data center.

EPI Data Center Specialist References:

EPI promotes the EoR design as a way to reduce switch counts and streamline management in data centers. This configuration allows for easier scaling and maintenance while maintaining efficient network connectivity.

Asrelative humiditydecreases,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.