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質問 # 12
The building in which the computer room is housed is required to have a sprinkler system. The building is therefore equipped with a wet pipe system.
What action, if any, should you recommend for the computer room?
- A. Maintain the current wet pipe system.
- B. Replace the wet pipe system with a dry pipe system.
- C. Replace the wet pipe system with a pre-action system.
- D. Replace the wet pipe system with a deluge system.
正解：C
解説：
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.
質問 # 13
Management has requested a 15-minute battery bank assuming full load on the UPS. The UPS vendor has provided the following specifications of the UPS:
* Rated power: 30 kVA
* Rectifier input voltage: 400 V/3 phase
* Rectifier input power factor: 0.8
* Battery rated voltage: 384 V
* Number of cells: 192
* End of discharge voltage: 308 V
* Inverter output voltage: 400 V/3 phase
* Inverter output power factor: 0.8
What information is missing to perform the battery calculation?
- A. Available battery charging current
- B. Load imbalance on the phases
- C. UPS efficiency
- D. Inverter efficiency
正解：C
解説：
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.
質問 # 14
You are working with a customer who requires a guarantee that THDi levels coming from the UPS should not exceed more than 3% THDi. Furthermore, he wants to run a power-efficient data center. The UPS has a 6-Pulse SCR/Thyristor based rectifier. The current load on the UPS is approximately 80%. The customer indicates they are not expecting any changes on the ICT infrastructure for the next 3 years.
What should you recommend?
- A. Nothing, the UPS will be able to take care of the right levels of THDi
- B. Install an isolation transformer rated at K13 or K20
- C. Install an active harmonic filter on the UPS
- D. Install a passive harmonic filter on the UPS
正解：C
解説：
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.
質問 # 15
What is the advantage or disadvantage of using MPO (Multi-fiber Push On)/pre-terminated fiber?
- A. It is a very flexible system as it can be used for both copper cables and optical fiber cables.
- B. It speeds up installation and provides an easy upgrade to transmission speeds up to 40 Gbit/s -100 Gbit
/s. - C. There is no advantage, as it creates additional heat load in the data center.
- D. There is no advantage, as it cannot be used with OM4 optical fiber cables.
正解：B
解説：
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.
質問 # 16
The logical overview of the data center looks as pictured. To what TIA-942 Rating is this design made based on electrical only?
- A. Rating - 2
- B. Rating - 1
- C. Rating - 3
- D. Rating - 4
正解：D
解説：
The electrical design shown in the diagrams represents a TIA-942 Rating-4 configuration. This design includes full redundancy and fault tolerance, as demonstrated by the dual power distribution paths from the utility supply to the critical loads. Each power distribution path is equipped 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:
A Rating-4 data 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.
質問 # 17
Three data centers are benchmarked on facilities energy efficiency.
Data center A has achieved a PUE of 2.45.
Data center B has achieved a PUE of 1.20.
Data center C has achieved a PUE of 1.90.
Which of the data centers is operating at the highest facility efficiency?
- A. PUE does not indicate efficiency
- B. Data center A
- C. Data center C
- D. Data center B
正解：B
解説：
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.
質問 # 18
The noise levels in the data center are approximately 91 dB (A).
Do employers need to take precautions?
- A. There are no regulations regarding noise levels inside a building. Regulations only apply to noise pollution outside of the building.
- B. No, anything less than 100 dB (A) is acceptable.
- C. As long as the data is compliant to ISO/IEC 27001 it is acceptable.
- D. Yes, since it is mandated by regulations.
正解：D
解説：
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.
質問 # 19
You are working on the design of a new facility. The electrical riser of the building with high current power is located close to the area where sensitive IT equipment in the computer room will be located.
What should you recommend to reduce the amount of EMF coming from the electrical riser?
- A. Install three-phase power cabling based on three individual core wires
- B. Install bus bar trunking
- C. Install single-phase power cabling
- D. Install three-phase power cabling based on a combined cable (e.g. XLPE etc.)
正解：D
解説：
To reduce Electromagnetic Fields (EMF) emanating from the electrical riser near 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 the overall 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.
質問 # 20
What should you consider when using raised floor tiles with air deflectors or louvers?
- A. Tiles with air deflectors or louvers do not allow for a flexible cooling solution.
- B. Tiles with air deflectors or louvers can only be used to cool storage equipment.
- C. Tiles with air deflectors or louvers can be very heavy.
- D. Tiles with air deflectors or louvers will reduce the cooling capacity of the tile.
正解：C
解説：
Raised floor tiles with air deflectors or louvers are typically heavier than standard tiles due to the additional materials and mechanisms used to direct airflow. The added weight can pose challenges for installation and adjustment, and consideration must be given to the floor's load capacity and ease of maintenance.
Detailed Explanation:
Tiles with deflectors or louvers help direct airflow, enhancing cooling efficiency by focusing cool air where needed. However, these tiles are often heavier, which can affect handling and require reinforced raised floor systems. It's essential to factor in the weight for any floor tile replacements or installations to ensure they are compatible with the raised floor's structural capacity.
EPI Data Center Specialist References:
EPI data center design training mentions the potential impact of heavy tiles on floor handling and load capacity. Data center operators need to plan for safe handling and load-bearing capacity when using such specialized tiles.
質問 # 21
You have three UPS systems connected in parallel. The UPS systems have an imbalance in the load sharing of approximately 20%.
What should you recommend?
- A. Nothing, there is no reason for any concern
- B. Review the cable lengths of each UPS to the common busbar
- C. Review the harmonics levels within the computer room
- D. Review the common mode noise levels within the computer room
正解：B
解説：
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.
質問 # 22
A computer room with a raised floor has been designed with racks in a hot/cold aisle setup.
What should you recommend for the placement of down-flow air conditioners?
- A. Air conditioners perpendicular to (at the end of the row of) the Cold-Aisle
- B. Air conditioner placement has no influence on cooling effectiveness and efficiency. Hence, they can be placed at any convenient location.
- C. Air conditioners should always be placed at both sides of each row of racks
- D. Air conditioners perpendicular to (at the end of the row of) the Hot-Aisle
正解：A
解説：
In a hot/cold aisle configuration, placing down-flow air conditioners perpendicular to the cold aisle ensures 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.
質問 # 23
When designing a data center network, your company wants to minimize the number of network switches to manage.
What type of physical cabling layout would be the best choice?
- A. Star network design using coaxial cables
- B. ToR (Top of Rack) design
- C. EoR (End of Row) design
- D. It does not matter as the number of switches is not influenced by the physical cabling layout
正解：C
解説：
An End of Row (EoR) design minimizes 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. This design 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.
質問 # 24
A 5kW (power consumption) server keeps crashing with the message 'temperature too high'.
The intake temperature is measured at 25 °C/77 °F and a relative humidity (RH) level of 50%.
The exhaust temperature is 29 °C/84 °F and 45% RH.
The raised floor is providing an adequate amount of CFM/CMH at a reasonable velocity.
The pressure under the raised floor is approximately 25 Pa/0.1 inch H#O.
Analyze the situation and indicate what the most likely cause is for this server to crash.
- A. Dust inside the server causing issues with convection-based heat transfer
- B. The exhaust temperature is exceeding the ASHRAE recommended values
- C. The raised floor pressure is too low and/or the raised floor tile % opening is not adequate
- D. No cause could be determined as the CFM/CMH of the air conditioning equipment is not stated
正解：A
解説：
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.
質問 # 25
Should aerosol cleaning solutions be used in the computer room?
- A. No, it will contaminate the room
- B. Yes, if not connected to power
- C. No, unless leak detection installed
- D. Yes, only if room smells bad
正解：A
解説：
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.
References: ASHRAE TC 9.9 "Contamination Guidelines," NFPA 75 §8.4.
質問 # 26
A new facility requires electrical distribution of 100A to be installed in the computer room, 1 m (3 ft) above sensitive IT equipment. What type of system minimizes EMF impact?
- A. Install three-phase power cabling based on a combined cable (e.g., XLPE)
- B. Install three-phase power cabling based on three individual core wires
- C. Install bus bar trunking
- D. Install single-phase power cabling
正解：A
解説：
Electromagnetic fields are generated by current-carrying conductors. To minimize stray EMF, phase conductors should be physically close and balanced. A three-phase combined cable (all phase conductors and neutral in one sheath) ensures magnetic fields cancel each other due to phase opposition.
If phases are run separately (answer B), the separation increases loop area and magnetic field leakage. Single- phase cabling (A) is even worse because current does not balance across three phases. Bus bar trunking (C) provides physical support but often separates conductors, which may worsen EMF if not specifically shielded.
Therefore, the correct solution is three-phase combined cable (often XLPE-insulated). This design reduces EMF impact to within ANSI/TIA-942 and IEEE recommendations.
References: IEEE Std 141 (Red Book - Power Distribution), ANSI/TIA-942-B §6.6.4, IEC 60364 (Wiring Systems and EMF).
質問 # 27
What mainly affects the cooling capacity of a raised floor tile?
- A. Percentage of the surface opening, airflow direction of the ICT equipment, temperature difference between the air intake and air exhaust of the ICT equipment, construction material of the tile
- B. Relative humidity in the computer room, temperature of the cold air, pressure under the raised floor, construction material of the tile
- C. Type of ICT equipment, location of the air conditioner, pressure under the raised floor, allowable temperature in the hot aisle
- D. Percentage of the surface opening, obstruction of the supporting construction, pressure under the raised floor, damper construction
正解：D
解説：
The cooling capacity of a raised floor tile is primarily influenced by the percentage of surface opening, the obstruction caused by the supporting construction, the pressure under the raised floor, and the damper 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:
The percentage of surface opening on a floor tile affects how much air can flow through, with larger openings allowing more airflow. Supporting structures beneath the floor can obstruct airflow, reducing cooling efficiency. Pressure under the raised floor impacts the velocity and volume of air that moves through the tile. Additionally, if dampers are 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.
質問 # 28
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