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CDCS Actual Questions - Instant Download 122 Questions

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NEW QUESTION # 35
Which of the following statements is correct?

• A. With current increasing, single-phase cables emit more EMF than three-phase cables
• B. With current decreasing, three-phase cables emit more EMF than single-phase cables
• C. With voltage decreasing, three-phase cables emit more EMF than single-phase cables
• D. With voltage increasing, single-phase cables emit more EMF than three-phase cables

Answer: A

Explanation:
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.
References: IEEE Std 141 (Red Book - Power Distribution), IEC 61000-5-7 (EMF mitigation guidelines), ANSI/TIA-942-B §6.6.

NEW QUESTION # 36
You want to manage temperature and humidity only at the facility level in your data center. All servers use front-to-rear airflow. Which location for measurement should you recommend?

• A. At the front/intake of the server at 50 mm (2 in)
• B. At 1.5 m (5 ft) above the floor, 0.4 m (15 in) at the back of the rack
• C. At the back/rear of the server at 50 mm (2 in)
• D. At 1.5 m (5 ft) above the floor, 0.4 m (15 in) in front of the rack

Answer: D

Explanation:
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).
References: ASHRAE TC 9.9 "Thermal Guidelines for Data Processing Environments" (2016), ANSI/TIA-
942-B §6.5.

NEW QUESTION # 37
The noise levels in the data center are approximately 91 dB (A).
Do employers need to take precautions?

• A. Yes, since it is mandated by regulations.
• B. There are no regulations regarding noise levels inside a building. Regulations only apply to noise pollution outside of the building.
• C. No, anything less than 100 dB (A) is acceptable.
• D. As long as the data is compliant to ISO/IEC 27001 it is acceptable.

Answer: A

Explanation:
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.

NEW QUESTION # 38
What is the effect of having a damper (in open position) construction in a raised-floor tile?

• A. Dampers reduce the air volume by approximately 10%
• B. Dampers allow for a higher supply air temperature
• C. Dampers increase the air volume by approximately 10%
• D. Dampers can be used when there is a high rate of temperature change in the computer room

Answer: A

Explanation:
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%.
References: ASHRAE TC 9.9 - "Airflow Management in Raised-Floor Environments," ANSI/TIA-942-B §6.
5 (Cooling Infrastructure).

NEW QUESTION # 39
Do you need to consider bullet (ballistic) protection when designing a data center?

• A. No, there is no reason for implementing bullet protection as you cannot predict the type of weapons that might be used
• B. Yes, bullet protection is a requirement of ANSI/TIA-942 for Rated-3/4 data centers
• C. Yes, but only when the data center is built in an area with a high criminality rate or with a risk of terrorist attacks
• D. No; bullet protection is not a requirement of ANSI/TIA-942

Answer: C

Explanation:
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).
References: ANSI/TIA-942-B §6.4 Physical Security (threat/risk assessment), ISO 31000 (risk management).

NEW QUESTION # 40
What is the main disadvantage of using a ToR (Top of Rack) design?

• A. A ToR (Top of Rack) switch has only optical interfaces.
• B. There will be more switches to manage.
• C. You need a separate rack to install all your ToR (Top of Rack) switches.
• D. A single ToR (Top of Rack) switch is more expensive than an EoR (End of Row) switch.

Answer: B

Explanation:
A Top of Rack (ToR) design typically requires more switches because each rack has its own switch to manage network connections, as opposed to End of Row (EoR) or centralized designs, which consolidate switches. While ToR designs improve cabling efficiency and reduce latency, they also increase the number of switches, thus raising management complexity and potentially increasing capital and operational costs.
Detailed Explanation:
In a ToR setup, each rack's individual switch allows for quick access and streamlined cabling within the rack. However, this setup means more devices to configure, monitor, and maintain, which can increase administrative overhead and network management complexity.
EPI Data Center Specialist References:
EPI documentation notes that ToR designs can improve performance but also lead to increased management needs due to the higher switch count, making them less ideal in environments where simplified network management is prioritized.

NEW QUESTION # 41
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 - 1
• B. Rating - 2
• C. Rating - 4
• D. Rating - 3

Answer: C

Explanation:
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.

NEW QUESTION # 42
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. Install an active harmonic filter on the UPS
• B. Install an isolation transformer rated at K13 or K20
• C. Install a passive harmonic filter on the UPS
• D. Nothing, the UPS will be able to take care of the right levels of THDi

Answer: A

Explanation:
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.

NEW QUESTION # 43
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 H₂O.
Analyze the situation and indicate what the most likely cause is for this server to crash.

• A. The raised floor pressure is too low and/or the raised floor tile % opening is not adequate
• B. No cause could be determined as the CFM/CMH of the air conditioning equipment is not stated
• C. Dust inside the server causing issues with convection-based heat transfer
• D. The exhaust temperature is exceeding the ASHRAE recommended values

Answer: C

Explanation:
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.

NEW QUESTION # 44
The computer room has high levels of H2S gas contamination. What is the best option to resolve this issue?

• A. Vacuum the whole room using a HEPA/S-Class-based filter.
• B. Clean the room and racks with a damp/wet cloth.
• C. Provide more air changes per hour by adding more fresh air to the computer room.
• D. Install air-scrubbers.

Answer: D

Explanation:
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.

NEW QUESTION # 45
You need to determine the strategy for the cooling audit. All the servers are based on a front-to-rear (F-R) airflow design.
Which location for the temperature/humidity measurement should you recommend for the audit?

• A. At 1.5 meters/5 feet above the floor in the middle of the hot aisle
• B. At 1.5 meters/5 feet above the floor in the middle of the cold aisle
• C. At the back/rear of the server at 50 mm/2 inch
• D. At the front/intake of the server at 50 mm/2 inch

Answer: D

Explanation:
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.

NEW QUESTION # 46
Management requests a 15-minute battery bank at full UPS load. UPS specs:
* 30 kVA, PF 0.8
* Battery 384 V (192 cells), end discharge 308 V
* Inverter PF 0.8, 400 V output
What information is missing to perform the calculation?

• A. Load imbalance
• B. Inverter efficiency / output PF
• C. UPS efficiency
• D. Available battery charging current

Answer: C

Explanation:
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 # = 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.
References: IEEE Std 1188 (VRLA Batteries), IEC 62040-3 (UPS performance), ANSI/TIA-942-B §6.2.

NEW QUESTION # 47
An MCB needs to be installed in the PDU of an air-conditioner unit.
Which breaking curve should you select?

• A. D-Curve
• B. C-Curve
• C. A-Curve
• D. B-Curve

Answer: B

Explanation:
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.

NEW QUESTION # 48
What is the floor loading requirement for a Rated-3 data center according to ANSI/TIA-942?

• A. 12 kPa
• B. 15 kPa
• C. 7.2 kPa
• D. 8.4 kPa

Answer: A

Explanation:
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.
References: ANSI/TIA-942-B §6.3.5 (Floor Loading), CISCA Raised Floor Design Guide.

NEW QUESTION # 49
A data center scores Rated-3 in mechanical, Rated-4 in electrical, and Rated-2 in telecommunications. What is the overall rating?

• A. Depends on architectural rating
• B. Rated-4
• C. Rated-4 since electrical is most important
• D. Rated-2

Answer: D

Explanation:
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.
References: ANSI/TIA-942-B §5.2.3 (Overall rating determination).

NEW QUESTION # 50
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. Replace the wet pipe system with a pre-action system.
• B. Replace the wet pipe system with a deluge system.
• C. Maintain the current wet pipe system.
• D. Replace the wet pipe system with a dry pipe system.

Answer: A

Explanation:
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.

NEW QUESTION # 51
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