CDCS Questions and Answers

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 afront-to-rear (F-R) airflow design, measuring at thefront/intake of the serverwill 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 humidity50 mm/2inches 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.

Whenshielding materialreaches itssaturation point, it can no longer effectively attenuate additional EMF. At saturation, the material’s ability to absorb or redirect magnetic fields is exhausted, meaning it cannot provide further shielding beyond this point. Additional EMF exposure would pass through the material without significant reduction.

Detailed Explanation:

Saturation occurs when the material’s magnetic domains are fully aligned with the magnetic field, leaving no capacity to absorb or deflect further EMF. This can happen with high EMF levels, beyond the material’s design limits, resulting in a breakdown of shielding effectiveness.

EPI Data Center Specialist References:

EPI guidelines on EMF management indicate that selecting appropriate shielding materials with sufficient capacity is essential to prevent saturation and ensure continuous protection. Saturation limits should be considered during design to avoid compromised shielding performance.

To reduceElectromagnetic Fields (EMF)emanating from theelectrical risernear sensitive IT equipment,three-phase power cabling in a combined cable(such as XLPE) is effective. Combined cabling helps reduce EMF by keeping the conductors tightly packed, which minimizes magnetic fields generated by current flow. Cables like XLPE (cross-linked polyethylene) also offer better insulation, which helps mitigate EMF interference with nearby IT equipment.

Detailed Explanation:

Using a combined three-phase cable reduces EMF because the magnetic fields generated by each phase tend to cancel each other out when in close proximity. This arrangement helps reduce theoverall magnetic field strength. In addition, XLPE and similar materials provide good insulation, making them a preferred choice for reducing EMF emissions around sensitive equipment.

EPI Data Center Specialist References:

EPI data center best practices recommend mitigating EMF interference through combined cabling arrangements, especially near areas where sensitive IT equipment is located. Reducing EMF is crucial to maintaining equipment reliability and ensuring compliance with safety standards.

For aUPS systemin aRating-4 data center, the synchronization of output can indeeddepend on the specific settingsof the UPS. Generally, such systems allow for flexible configuration where the output can be synchronized to eitherpower feed A or B, depending on which feed is preferred for stability or redundancy purposes.

Detailed Explanation:

In dual-feed setups, such as those in high-redundancy data centers, the UPS can be set to synchronize with either feed. This ensures that the UPS maintains continuity in case one feed becomes unstable or fails. The flexibility to choose synchronization to either feed enhances theresiliency and reliability of power supply, which is critical in Tier IV (Rating-4) facilities where uptime is paramount.

EPI Data Center Specialist References:

The EPI Data Center Specialist course underscores the importance of configurable UPS systems in Rating-4 data centers, where redundancy and continuous power are critical. By allowing synchronization to either feed, the UPS can maintain the highest level of reliability, which aligns with the rigorous standards expected in such environments.

Theserver’s repeated overheatingdespite adequate intake and exhaust temperatures suggests thatdust buildup inside the servermay 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.

When installing araised floor, the best starting point is typicallyfrom 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 controlledplacement 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.

In areas with frequent and extended power outages,continuous generatorswith at least anN+1 configurationare necessary to ensure consistent power availability. Continuous generators are designed for prolonged operation, making them suitable for scenarios where utility power is frequently unavailable, as in this case with outages exceeding 650 hours per year. An N+1 configuration ensures redundancy, which is critical for maintaining uptime in a high-availability data center.

Detailed Explanation:

Continuous generators provide reliable power over long durations, unlike standby generators, which are intended only for short-term use. The N+1 configuration ensures that there is always an additional generator available in case of failure, thus maintaining power supply even if one generator goes offline.

EPI Data Center Specialist References:

EPI best practices recommend continuous generators with redundancy for data centers located in areas with high power instability to maintain reliability and continuous operation.

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.

Aspirit level barshouldnot be usedfor leveling a raised floor, asmeasurement errorsare likelytopropagatefrom one pedestal to the next. Spirit levels can introduce cumulative errors, leading to uneven floors, particularly in large installations where precise leveling is critical.

Detailed Explanation:

Using a laser level or a precision leveling device is recommended to ensure accuracy across all floor tiles. Spirit levels, while adequate for short spans, can transfer small inaccuracies from one pedestal to another, which can cause alignment issues and floor instability over time.

EPI Data Center Specialist References:

EPI data center guidelines discourage the use of spirit levels for raised floors. Instead, they advocate for precision tools like laser levels that ensure consistency and accuracy in large-scale installations, aligning with best practices for raised floor construction.

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.

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.

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.

In a data center with noise levels of 91 dB (A), employers are indeed required to take precautions to protect personnel, as this level exceeds commonly accepted safety thresholds for occupational noise exposure. Regulations, such as those from the Occupational Safety and Health Administration (OSHA) or similar agencies, mandate specific controls and protections for environments with high noise levels.

Detailed Explanation:

Noise levels above 85 dB (A) typically trigger requirements for hearing conservation programs. At 91 dB (A), steps like providing ear protection, conducting regular noise assessments, and possibly implementing engineering controls to reduce noise should be taken. Extended exposure to such levels can lead to hearing loss, so regulatory compliance ensures both immediate and long-term protection for personnel.

EPI Data Center Specialist References:

EPI guidelines for data center safety address noise exposure as part of the environmental safety measures. EPI recommends adhering to local occupational health regulations, as excessive noise can harm personnel and affect operational efficiency due to potential health hazards.