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EPI Data Centre Foundation practice questions

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Question 1Data Centre Design and Infrastructure

Which tier classification does the Uptime Institute use for a data centre that has redundant capacity components and multiple independent distribution paths serving the IT equipment, allowing concurrent maintenance of any component?

  1. Tier II
  2. Tier I
  3. Tier III Correct answer.
  4. Tier IV

Explanation

Tier III (Concurrently Maintainable) permits any capacity component or distribution path to be taken offline for planned maintenance without shutting down IT load, and requires multiple independent distribution paths. Tier IV adds fault tolerance against unplanned failures. Tier II only adds redundant components without redundant paths.

Question 2Data Centre Design and Infrastructure

In a raised-floor data centre, what is the primary purpose of the plenum beneath the floor tiles?

  1. To house the fire suppression water tanks
  2. To store spare network cabling
  3. To distribute conditioned cooling air to perforated tiles near IT equipment Correct answer.
  4. To provide structural support for the ceiling grid

Explanation

The sub-floor void acts as an air distribution plenum, delivering cold air from CRAC/CRAH units to perforated or grille tiles positioned in cold aisles. Cable trays may run there but that is a secondary use. Water tanks and ceiling support are unrelated functions.

Question 3Data Centre Design and Infrastructure

A rack draws 8 kW and the facility provides chilled water at 12 degrees C with an air-side economizer. Which cooling approach is most appropriate for this density?

  1. Room-level perimeter CRAC units only
  2. In-row or rear-door heat exchangers close to the load Correct answer.
  3. Passive chimney cabinets with no mechanical cooling
  4. Open windows with filtered fans

Explanation

At 8 kW per rack, room-level perimeter cooling struggles to deliver adequate airflow and temperature uniformity, so close-coupled solutions such as in-row coolers or rear-door heat exchangers are preferred. Passive chimneys rely on an upstream cooling source and do not remove heat themselves. Open windows are not a controlled data centre cooling strategy.

Question 4Data Centre Design and Infrastructure

What does a PUE value of 1.4 indicate about a data centre?

  1. IT equipment consumes 1.4 times the total facility power
  2. The data centre is 140 percent occupied
  3. Total facility power is 1.4 times the IT equipment power Correct answer.
  4. Cooling accounts for exactly 40 percent of IT load

Explanation

Power Usage Effectiveness equals total facility energy divided by IT equipment energy, so 1.4 means the facility draws 40 percent more power than the IT load alone. It says nothing directly about occupancy or the split between cooling and other overheads. A value of 1.0 would represent perfect efficiency.

Question 5Data Centre Design and Infrastructure

Which redundancy topology is described by the notation N+1 for a UPS system?

  1. No redundancy, with modules loaded to maximum
  2. One UPS module in excess of the number needed to carry the load Correct answer.
  3. Two completely independent UPS systems each sized for full load
  4. Redundancy that only applies to the bypass path

Explanation

N+1 means the installed capacity equals the required capacity N plus one additional module, so a single module can fail or be maintained without losing load support. Two fully independent full-load systems would be 2N. No redundancy is simply N.

Question 6Data Centre Design and Infrastructure

Why are cold aisles and hot aisles arranged in alternating rows in a data hall?

  1. To prevent hot exhaust air from mixing with cold supply air Correct answer.
  2. To shorten cable runs between cabinets
  3. To simplify fire zone boundaries
  4. To reduce the structural floor loading

Explanation

Alternating rows place equipment intakes facing a common cold aisle and exhausts facing a common hot aisle, which limits recirculation and mixing that would raise intake temperatures. Cable length, fire zoning, and floor loading are unrelated to aisle orientation. Containment often supplements this arrangement.

Question 7Data Centre Design and Infrastructure

A data centre uses N+1 UPS modules but a single power distribution path to each rack via one PDU. Which statement best characterises the resulting availability?

  1. Redundant UPS capacity exists but the single distribution path remains a single point of failure Correct answer.
  2. The UPS redundancy eliminates the need for dual-corded servers
  3. The power chain is fully fault tolerant end to end
  4. The single PDU path automatically provides 2N redundancy

Explanation

Redundancy must be evaluated across the whole chain; a single PDU and path means a failure there drops the load regardless of UPS redundancy. Full fault tolerance requires independent distribution paths, typically A and B feeds to dual-corded equipment. UPS module redundancy alone cannot compensate for a downstream single point of failure.

Question 8Data Centre Design and Infrastructure

Which fire suppression agent is most commonly selected for occupied data halls because it leaves no residue on electronics?

  1. Clean agent such as an inert gas or fluorinated ketone Correct answer.
  2. Dry chemical powder
  3. Foam
  4. Water deluge sprinklers

Explanation

Clean agents extinguish fire without leaving conductive or corrosive residue, protecting IT equipment and allowing safe discharge in occupied spaces at design concentrations. Water deluge, dry powder, and foam all leave residue or cause water damage. Pre-action sprinklers are used as backup but are not a clean agent.

Question 9Data Centre Design and Infrastructure

What is the main function of a pre-action sprinkler system in a data centre?

  1. To hold water out of the piping until a detection signal confirms a fire Correct answer.
  2. To replace clean agent suppression entirely
  3. To discharge water immediately when a single smoke detector alarms
  4. To cool the room during a cooling failure

Explanation

A pre-action system keeps the pipes dry and requires a detection signal (often two independent detectors) before water fills the piping, reducing the risk of accidental discharge. It then acts as a conventional sprinkler. It complements rather than replaces clean agent and does not provide cooling.

Question 10Data Centre Design and Infrastructure

Which cabling practice best supports a 2N power architecture to servers?

  1. All servers fed from one busway with a single upstream breaker
  2. Each server power supply connected to a separate PDU fed from an independent source Correct answer.
  3. Both power supplies of each server plugged into the same PDU
  4. Power supplies connected in series to share load

Explanation

To realise 2N, each of the two server power supplies must connect to a different PDU whose upstream path is independent, so a fault on one path leaves the other feeding the load. Plugging both cords into one PDU or one busway collapses the redundancy. Server supplies are not wired in series.

Question 11Data Centre Design and Infrastructure

A UPS rated 500 kVA at a power factor of 0.9 delivers what real power output at full rating?

  1. 450 kW Correct answer.
  2. 900 kW
  3. 500 kW
  4. 555 kW

Explanation

Real power equals apparent power times power factor, so 500 kVA multiplied by 0.9 gives 450 kW. The 500 kW figure ignores the power factor, and 555 kW divides instead of multiplying. The 900 kW value has no basis in the given figures.

Question 12Data Centre Design and Infrastructure

Which statement correctly describes the role of a static transfer switch (STS) in a data centre power chain?

  1. It steps up voltage for long cable runs
  2. It rapidly transfers load between two independent power sources Correct answer.
  3. It stores energy during a utility outage
  4. It converts AC to DC for the servers

Explanation

An STS switches the load from a preferred source to an alternate source within a few milliseconds when the preferred source fails or drifts out of tolerance. It does not rectify AC to DC, transform voltage, or store energy; those are functions of rectifiers, transformers, and batteries respectively.

Question 13Data Centre Design and Infrastructure

Which environmental monitoring parameter is most directly linked to the risk of electrostatic discharge damaging components?

  1. Air velocity in the cold aisle
  2. Differential pressure across containment
  3. Relative humidity Correct answer.
  4. Ambient sound level

Explanation

Low relative humidity increases static charge accumulation and the risk of electrostatic discharge, which is why standards set a lower humidity bound. Air velocity, pressure differentials, and sound level affect cooling and comfort but not ESD risk directly.

Question 14Data Centre Design and Infrastructure

A data hall has containment on the hot aisle and a perforated tile layout. What is the most likely consequence of leaving several tiles removed in a cold aisle?

  1. Increased cold air bypass into the room, reducing cooling at the racks Correct answer.
  2. Improved airflow uniformity across all racks
  3. Higher static pressure at the CRAC units with no effect on racks
  4. Reduced fire suppression coverage only

Explanation

Missing tiles create a path for conditioned air to escape into the room without passing through equipment, which is cold air bypass. This lowers the pressure available at the perforated tiles and starves the racks of airflow. It does not improve uniformity and has no direct suppression effect.

Question 15Data Centre Design and Infrastructure

Which metric measures the highest temperature at the air intake of IT equipment and is used to validate cooling performance against ASHRAE guidance?

  1. Supply air temperature at the CRAC
  2. Return air temperature
  3. Chilled water supply temperature
  4. Rack inlet temperature Correct answer.

Explanation

Rack inlet temperature reflects what the IT equipment actually ingests and is compared against ASHRAE recommended and allowable ranges. CRAC supply temperature is measured before mixing and bypass occur, so it can understate rack intake conditions. Return and chilled water temperatures are not equipment intake measures.

Question 16Data Centre Design and Infrastructure

Which of the following best explains why a data centre might adopt a 2N electrical topology rather than N+1?

  1. To reduce capital cost by removing redundant components
  2. To increase PUE for reporting purposes
  3. To tolerate the failure or maintenance of an entire distribution system, not just a single component Correct answer.
  4. To eliminate the need for a generator

Explanation

2N provides two complete, independent systems each capable of carrying the full load, so an entire system can be taken down without affecting IT. N+1 only tolerates a single component failure within one system. 2N increases rather than reduces capital cost and does not remove the need for backup generation.

Question 17Data Centre Design and Infrastructure

What is the primary benefit of aisle containment in a data hall?

  1. It reduces the fire suppression agent required
  2. It replaces the need for any CRAC units
  3. It prevents mixing of cold supply and hot exhaust air, improving cooling efficiency Correct answer.
  4. It increases the structural load rating of the floor

Explanation

Containment physically separates cold supply from hot exhaust, reducing recirculation and allowing higher supply temperatures and better efficiency. It does not change floor loading, eliminate mechanical cooling, or determine suppression agent quantities. It is a complement to correct aisle layout.

Question 18Data Centre Design and Infrastructure

Which statement about a flywheel-based UPS compared with a battery-based UPS is accurate?

  1. The flywheel cannot support a static transfer switch
  2. The flywheel stores kinetic energy and typically provides shorter ride-through Correct answer.
  3. The flywheel requires more maintenance of lead-acid cells
  4. The flywheel provides longer ride-through than a battery string

Explanation

A flywheel stores rotational kinetic energy and bridges brief outages, usually seconds, which is enough to ride through to generator start. Batteries typically provide longer ride-through but require periodic cell maintenance. Flywheels avoid lead-acid cells and work fine with transfer switches.

Question 19Data Centre Design and Infrastructure

A generator serving a data centre must start and accept load within a defined time. Which parameter most directly determines whether a UPS battery string is sized adequately for that gap?

  1. UPS output voltage regulation
  2. Generator alternator power factor
  3. Generator fuel tank capacity
  4. Autonomy time at full load Correct answer.

Explanation

Battery autonomy at full load must exceed the time from utility loss to generator acceptance of load, including any retries. Fuel capacity affects long-duration runtime after the generator is running, not the initial gap. Alternator power factor and voltage regulation do not determine the bridge time.

Question 20Data Centre Design and Infrastructure

Which practice is recommended for managing cable airflow obstructions under a raised floor?

  1. Blocking perforated tiles near high-density racks
  2. Removing all tiles to increase airflow
  3. Filling the plenum completely with bundled cables
  4. Using cable trays and sealing penetrations to preserve air paths Correct answer.

Explanation

Organised cable trays and sealed penetrations keep the plenum clear so air can reach perforated tiles without excessive pressure loss. Filling the plenum or removing tiles creates bypass and turbulence. Blocking tiles near high-density racks would starve the equipment that needs airflow most.

Question 21Data Centre Design and Infrastructure

Which standard family provides guidance on data centre facility topology, including power and cooling infrastructure classifications?

  1. ANSI/TIA-942 Correct answer.
  2. ISO 27001
  3. IEEE 802.3
  4. PCI DSS

Explanation

ANSI/TIA-942 covers data centre infrastructure including site topology, power, cooling, and cabling, with its own tier ratings. ISO 27001 addresses information security management, IEEE 802.3 defines Ethernet, and PCI DSS governs payment card data security. Only TIA-942 is a facility topology standard.

Question 22Data Centre Design and Infrastructure

What is the purpose of an economizer in a data centre cooling system?

  1. To filter particulate contamination from the room
  2. To use outside air or water-side cooling when conditions allow, reducing mechanical cooling energy Correct answer.
  3. To provide backup power during a utility outage
  4. To increase the chilled water temperature setpoint permanently

Explanation

An economizer exploits favourable outdoor conditions, using free cooling via air or water to reduce compressor or chiller operation and lower energy use. It does not set chilled water temperatures permanently, provide electrical backup, or serve as the primary filtration system.

Question 23Data Centre Design and Infrastructure

A data centre reports a PUE of 1.1 in winter and 1.6 in summer. Which explanation is most plausible?

  1. The UPS efficiency drops to zero in summer
  2. The power factor of servers changes seasonally
  3. Free cooling reduces mechanical cooling energy in winter, lowering overhead Correct answer.
  4. The IT load doubles in summer

Explanation

Lower winter PUE is consistent with economizer or free-cooling operation that cuts mechanical cooling overhead. IT load changes and UPS efficiency do not typically swing PUE by that margin, and server power factor is not a seasonal driver of facility overhead. PUE measures overhead relative to IT load.

Question 24Data Centre Design and Infrastructure

Which of the following is a typical function of a building management system (BMS) in a data centre?

  1. Monitoring and controlling cooling, power, and environmental conditions Correct answer.
  2. Encrypting data at rest on storage arrays
  3. Managing user authentication to applications
  4. Routing IP traffic between server VLANs

Explanation

A BMS supervises mechanical and electrical plant such as chillers, CRAC units, generators, and environmental sensors, and raises alarms on out-of-tolerance conditions. Network routing, storage encryption, and application authentication belong to IT systems, not the building management layer.

Question 25Data Centre Design and Infrastructure

Which consideration most strongly favours liquid cooling over air cooling for a new high-density deployment?

  1. Liquid cooling eliminates the need for any redundancy
  2. Liquid cooling removes the need for environmental monitoring
  3. Liquid cooling can remove heat at densities beyond practical air-cooling limits Correct answer.
  4. Liquid cooling has no maintenance requirements

Explanation

Direct-to-chip or immersion liquid cooling can reject heat from racks well beyond the practical limits of air cooling, which becomes constrained by airflow and temperature rise. Liquid cooling does not remove redundancy, monitoring, or maintenance needs; those remain essential.

Question 26Data Centre Design and Infrastructure

In data centre design, what does the rated short-circuit withstand current of a low-voltage switchboard indicate?

  1. The continuous load current the busbars can supply to IT racks under normal operation
  2. The surge current the assembly can absorb from a direct lightning strike on the roof
  3. The current at which protective devices must trip to protect downstream servers
  4. The maximum fault current the assembly can carry briefly without mechanical or thermal damage Correct answer.

Explanation

Short-circuit withstand rating (often expressed as Icw for a defined duration, typically 1 second) describes how much fault current the assembly tolerates while remaining safe and functional. It is a fault-condition property, distinct from the continuous current rating used for normal loading. Designers compare it against the prospective fault current at the installation point.

Question 27Data Centre Design and Infrastructure

A colocation provider wants each customer rack to be fed from two independent UPS systems with no shared conductive path upstream of the rack. Which power distribution design satisfies this?

  1. Two UPS systems each feeding its own PDU and rack inlet, routed on separate cable trays Correct answer.
  2. Two UPS modules operating in parallel on a common output busbar
  3. A single UPS with dual output breakers feeding two separate rack PDUs
  4. One UPS plus a generator that transfers load automatically on mains failure

Explanation

Full redundancy to the rack requires two separate power paths, each with its own UPS, distribution board, PDU and cabling route, so a fault in one path cannot affect the other inlet. Sharing a busbar or output breaker reintroduces a single point of failure. Physical route separation also protects against accidental damage to one path.

Question 28Data Centre Design and Infrastructure

Why is a raised floor with perforated tiles typically avoided in a hall designed for very high power density per rack?

  1. Raised floors are prohibited by fire codes in occupied data halls
  2. Perforated tiles cannot be bonded to the earthing grid
  3. The underfloor plenum cannot deliver enough cool air volume and pressure at high density Correct answer.
  4. Air delivered through tiles cannot be filtered to the required standard

Explanation

At high density the required airflow exceeds what a typical underfloor plenum can supply at usable static pressure, leading to hot spots at the top of racks. Designs shift to in-row or rear-door cooling, or containment with direct air delivery. Plenum capacity, not tile bonding or filtration, is the limiting factor.

Question 29Data Centre Design and Infrastructure

Which containment configuration places the perforated or grille floor tiles inside the enclosed volume?

  1. Rack-level rear-door heat exchanger
  2. Cold aisle containment Correct answer.
  3. Chimney-based exhaust containment
  4. Hot aisle containment

Explanation

In cold aisle containment the cold supply air is enclosed, so the perforated tiles that deliver it sit within the contained aisle. Hot aisle containment instead encloses the exhaust side and leaves the cold aisle open to the room. This distinction determines where tiles and return paths are placed.

Question 30Data Centre Design and Infrastructure

A design specifies a UPS system with a 10-minute battery autonomy at full load. What does this primarily determine?

  1. The interval between mandatory battery capacity tests
  2. The maximum permitted transfer time of the static transfer switch
  3. The time available to ride through short mains disturbances and start generators Correct answer.
  4. The maximum time the site can operate indefinitely without utility power

Explanation

Battery autonomy at full load sets the ride-through window before the UPS exhausts its stored energy, which must exceed generator start and stabilisation time. It does not provide indefinite operation, which depends on the generator and fuel supply. Transfer times of static switches are in milliseconds and unrelated to autonomy.

Question 31Data Centre Design and Infrastructure

Which characteristic most strongly distinguishes a lithium-ion battery string from a flooded lead-acid string in a UPS application?

  1. Lithium-ion strings require regular water topping up
  2. Lithium-ion strings cannot be installed in a data hall
  3. Lithium-ion strings have a lower energy density per unit volume
  4. Lithium-ion strings need a battery management system to monitor and balance cells Correct answer.

Explanation

Lithium-ion strings depend on a battery management system for cell-level monitoring, balancing and protection because of the chemistry's sensitivity to overvoltage and thermal events. They are sealed, need no watering, and have higher energy density than lead-acid. Fire code treatment differs but installation in data halls is permitted with appropriate measures.

Question 32Data Centre Design and Infrastructure

A data centre is in a region where the utility supply is reliable but the local grid suffers frequent short voltage sags. Which investment most directly addresses the sags?

  1. A larger fuel tank for the standby generators
  2. A second utility feed from the same substation
  3. Additional mechanical cooling capacity
  4. A UPS with adequate ride-through and fast transfer characteristics Correct answer.

Explanation

Voltage sags are short-duration events, and a UPS with sufficient ride-through keeps IT load supported until the sag passes or the generator takes over. Generators address outages, not brief sags, and fuel capacity is irrelevant to a seconds-long event. A second feed from the same substation shares the same disturbance source.

Question 33Data Centre Design and Infrastructure

What is the purpose of an equipotential bonding network (earthing grid) beneath a raised floor in a data hall?

  1. To carry operational load current back to the transformer
  2. To keep all metallic parts at a similar potential and limit potential differences Correct answer.
  3. To provide a return path for UPS battery charging current
  4. To reduce the acoustic noise from cooling fans

Explanation

A bonding network ties racks, cable trays, cabinets and structural metal together so that fault or static events do not create dangerous potential differences across equipment. It is not a current-carrying conductor under normal operation. This supports both personnel safety and reliable IT operation.

Question 34Data Centre Design and Infrastructure

Which fire detection approach is best suited to detecting a smouldering cable fault inside a data hall before visible flames appear?

  1. Aspirating smoke detection sampling air from the ceiling void and racks Correct answer.
  2. Optical flame detection aimed at the rack fronts
  3. Fixed-temperature heat detection on the ceiling
  4. Manual call points at the room exits

Explanation

Aspirating smoke detection continuously samples air and can detect very low smoke concentrations long before visible fire, which suits the incipient stage of cable faults. Heat and flame detectors respond only once significant heat or flame exists. Manual call points rely on a person noticing the event.

Question 35Data Centre Design and Infrastructure

In a data centre cooling design, what does the term 'delta-T' refer to when used to assess air-side efficiency?

  1. The difference between indoor and outdoor design temperatures
  2. The difference between the setpoint and the actual room temperature
  3. The temperature rise across the chilled water pump
  4. The difference between supply and return air temperatures across the IT load Correct answer.

Explanation

Air-side delta-T is the temperature rise of air as it passes through the IT equipment, from cold aisle supply to hot aisle return. A low delta-T for a given heat load indicates excess airflow and wasted fan energy. It is a key indicator used in cooling optimisation.

Question 36Data Centre Design and Infrastructure

A chilled water system uses a primary-secondary pumping arrangement. What is the main benefit of this configuration in a data centre?

  1. It eliminates the need for a thermal storage tank
  2. It guarantees that no pump can ever fail without losing cooling
  3. It decouples the chiller plant from the varying flow demanded by the terminal units Correct answer.
  4. It removes the need for any control valves on the cooling coils

Explanation

Primary-secondary pumping uses a hydraulic decoupler so chillers see constant primary flow while secondary pumps vary flow to match cooling coil demand. This avoids starving chiller evaporators when terminal valves modulate. It does not remove control valves, guarantee redundancy, or relate directly to thermal storage.

Question 37Data Centre Design and Infrastructure

What is the main purpose of a computational fluid dynamics (CFD) study during data hall design?

  1. To size the UPS battery strings for the required autonomy
  2. To determine the structural loading of the raised floor
  3. To calculate the short-circuit current at each distribution board
  4. To predict air velocity and temperature distributions before the hall is built Correct answer.

Explanation

CFD models airflow and heat transfer in the hall, letting designers test tile layouts, containment and cooling placement before construction. It reveals likely hot spots and bypass airflow that simple calculations miss. It does not address electrical fault levels, battery sizing, or structural loading.

Question 38Data Centre Design and Infrastructure

Which design feature most directly limits the spread of a fire from a data hall to an adjacent electrical room?

  1. Additional air filters in the recirculation path
  2. A raised floor with a higher plenum height
  3. Larger UPS battery strings for longer autonomy
  4. A fire-rated separation with sealed penetrations at the boundary Correct answer.

Explanation

Compartmentation relies on rated walls or floors and sealed cable and duct penetrations so fire and smoke cannot pass into adjacent spaces. Penetration sealing is essential because unprotected openings defeat the rating. Filters, plenum height and battery sizing do not provide fire separation.

Question 39Data Centre Design and Infrastructure

An operator wants to reduce water consumption in a cooling system while retaining mechanical cooling capability. Which design choice best matches that goal?

  1. An open cooling tower loop with no water treatment
  2. A larger evaporative condenser sized for peak wet-bulb
  3. A once-through cooling arrangement using potable water
  4. An air-cooled chiller plant combined with economiser operation Correct answer.

Explanation

Air-cooled chillers avoid evaporative water losses, and economiser operation reduces mechanical run hours when outdoor conditions allow. This combination lowers water use while keeping mechanical cooling available. Evaporative and once-through systems consume water by design.

Question 40Data Centre Design and Infrastructure

Which statement best describes the role of a data centre infrastructure management (DCIM) system in physical infrastructure operations?

  1. It provides inventory, capacity and connectivity visibility across power, cooling and space Correct answer.
  2. It replaces the building management system for controlling chillers
  3. It encrypts data at rest on the servers in the hall
  4. It performs automated failover of application workloads between sites

Explanation

DCIM tools track assets, power and cooling capacity, rack space and cabling connections so operators can plan changes and avoid overloading circuits or cooling zones. Control of plant remains with the BMS, and application failover is a separate IT function. DCIM is about physical infrastructure visibility.

Question 41Data Centre Design and Infrastructure

A rack draws 15 kW and the chosen in-row cooler provides 12 kW of cooling at design conditions. What is the most appropriate design response?

  1. Lower the chilled water supply temperature without checking capacity
  2. Accept the shortfall because in-row units are always oversized
  3. Add cooling capacity or reduce rack density to cover the deficit Correct answer.
  4. Remove containment to improve mixing

Explanation

Cooling capacity must meet or exceed the design heat load with margin, so the deficit must be closed by adding capacity or lowering density. Removing containment worsens hot spots by allowing mixing. Lowering supply temperature does not increase the unit's rated capacity and may cause other issues.

Question 42Data Centre Design and Infrastructure

What is the purpose of a neutral earthing resistor in a medium-voltage distribution system feeding a data centre?

  1. To improve the power factor of the UPS load
  2. To limit earth fault current and reduce damage at the fault point Correct answer.
  3. To provide backup power during a utility outage
  4. To step down the voltage for the low-voltage switchboard

Explanation

A neutral earthing resistor restricts earth fault current to a controlled level, reducing damage to equipment and improving safety while still allowing detection. Power factor correction and voltage transformation are separate functions. Backup power comes from UPS and generators.

Question 43Data Centre Design and Infrastructure

Which design practice best reduces the risk of a single cable tray fire disabling both A and B power feeds to a rack row?

  1. Using a single tray but colour-coding the cables
  2. Routing A and B feeds on separate trays with physical and fire separation Correct answer.
  3. Bundling A and B feeds together to simplify maintenance
  4. Installing both feeds on the same tray with fire-stop tape

Explanation

Redundant feeds only deliver their intended benefit if a single event cannot damage both, so separate routes with fire separation are required. Bundling or colour-coding on one tray leaves both feeds exposed to the same fire or mechanical damage. Fire-stop tape does not provide route separation.

Question 44Data Centre Design and Infrastructure

Which factor most directly determines the required capacity of a data hall's make-up air system?

  1. The rating of the UPS modules
  2. The design occupancy and the required air change rate for pressurisation and ventilation Correct answer.
  3. The number of racks installed in the hall
  4. The length of the cable trays in the hall

Explanation

Make-up air must supply ventilation for occupants and maintain positive pressure relative to adjacent spaces, so occupancy and air change requirements drive its capacity. Rack count affects cooling load, not ventilation demand directly. UPS ratings and cable tray length are unrelated.

Question 45Data Centre Design and Infrastructure

What is the main reason for maintaining positive pressure in a data hall relative to adjacent corridors?

  1. To speed up the response of the fire detection system
  2. To lower the electrical load of the UPS
  3. To reduce the ingress of dust and untreated air through openings Correct answer.
  4. To increase the cooling capacity of the CRAC units

Explanation

Positive pressure causes air to flow outward through gaps and doorways, limiting the entry of dust, humidity and untreated air that could affect IT equipment. It does not change cooling capacity or electrical load. Fire detection response is independent of room pressure.

Question 46Data Centre Design and Infrastructure

A site uses free cooling with an air-side economiser. Which condition most limits its hours of useful operation?

  1. The number of racks in the hall
  2. The rating of the standby generator
  3. High outdoor humidity combined with a low allowed indoor dew point Correct answer.
  4. A high UPS load factor during working hours

Explanation

Air-side economisers can only be used when outdoor air can be filtered and conditioned to stay within the hall's temperature and humidity envelope. High humidity with a low allowable dew point forces mechanical dehumidification or restricts economiser use. UPS load, rack count and generator rating do not govern economiser hours.

Question 47Data Centre Design and Infrastructure

Which statement correctly describes the difference between a maintenance bypass panel and a static transfer switch in a UPS system?

  1. The bypass panel provides a manual, break-before-make path around the UPS for servicing; the STS transfers load between two live sources automatically Correct answer.
  2. Both devices perform identical functions and differ only in physical size
  3. The STS isolates the UPS for maintenance while the bypass panel balances load between phases
  4. The bypass panel transfers load in milliseconds; the STS is operated manually by an engineer

Explanation

A maintenance bypass is a manually operated arrangement that lets the UPS be isolated and serviced while load is fed from utility or another source, typically with a brief interruption. A static transfer switch uses thyristors to move load between two available sources quickly and automatically. The two serve different purposes.

Question 48Data Centre Design and Infrastructure

What does a Tier III topology primarily provide compared with Tier II?

  1. A single non-redundant path with no maintenance capability
  2. Site infrastructure that can be shut down completely for maintenance
  3. Full fault tolerance with no single point of failure at any level
  4. Concurrently maintainable site infrastructure with redundant capacity components and multiple distribution paths Correct answer.

Explanation

Tier III adds redundant capacity components and multiple independent distribution paths so any component can be maintained while the site remains operational. Tier II adds redundant components but keeps a single distribution path. Full fault tolerance corresponds to Tier IV, and a single path describes Tier I.

Question 49Data Centre Design and Infrastructure

Which practice best protects a data hall's humidity envelope during winter in a cold climate?

  1. Sealing the hall completely with no ventilation
  2. Raising the cold aisle temperature setpoint to the maximum allowed
  3. Using humidification control with economiser operation and monitoring indoor dew point Correct answer.
  4. Increasing outdoor air intake to save on mechanical cooling

Explanation

Cold, dry outdoor air used for free cooling can drop indoor humidity below the allowed range, raising electrostatic discharge risk, so humidification and dew point monitoring are needed. Simply increasing outdoor air worsens dryness. Sealing the hall without ventilation is not acceptable for occupancy, and raising setpoints does not address humidity.

Question 50Data Centre Design and Infrastructure

What is the primary function of a leakage detection system under a raised floor in a data hall?

  1. To detect smoke from cable faults in the plenum
  2. To monitor the earthing continuity of the raised floor
  3. To measure the airflow rate through perforated tiles
  4. To detect water from condensate or pipe leaks before it reaches equipment Correct answer.

Explanation

Leak detection uses sensing cable or spot sensors under the floor to raise an alarm when water from chilled water pipework, condensate drains or roof leaks appears. Early warning allows intervention before equipment is affected. Smoke detection, airflow measurement and earthing checks are separate systems.