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Maine Low Voltage Practice practice questions

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Question 1Electrical Installation Standards (NFPA 70, National Electrical Code)

Under NEC Article 725, which Class designation applies to circuits that are power-limited and operate at 30 volts or less, where the circuit is not a Class 2 or 3 circuit and is not a fire alarm circuit?

  1. Class 2
  2. Class 3
  3. Class 1 Correct answer.
  4. Class 4

Explanation

Article 725 divides remote-control and signal circuits into Class 1, Class 2, and Class 3. Class 1 circuits are the general-purpose power-limited circuits that are not Class 2 or 3, and they carry higher energy than Class 2 or 3 circuits. Class 4 is not an Article 725 classification.

Question 2Electrical Installation Standards (NFPA 70, National Electrical Code)

For a low-voltage installation, what does the NEC define as the maximum voltage for a Class 2 circuit?

  1. 1000 volts
  2. 600 volts
  3. 30 volts Correct answer.
  4. 150 volts

Explanation

Class 2 circuits are power-limited and are generally limited to 30 volts or less under the Class 2 power source tables in Article 725. The voltage limit works together with current and power limits to define a Class 2 circuit. Higher voltages apply to Class 1 and Class 3 circuits.

Question 3Electrical Installation Standards (NFPA 70, National Electrical Code)

When Class 2 circuit conductors are installed in a raceway with Class 1 circuit conductors, which requirement governs their separation?

  1. They may be mixed only if the Class 1 circuit operates at less than 30 volts.
  2. They must be separated by a barrier or installed in separate raceways unless the Class 2 conductors are listed for the purpose. Correct answer.
  3. They may be mixed only if the raceway is metallic.
  4. They may be mixed freely in any raceway.

Explanation

Article 725 generally requires Class 2 and Class 3 conductors to be separated from Class 1 and power conductors by a barrier or by using separate raceways or cables. Mixing is permitted only where the Class 2 conductors are listed for the purpose or where specific exceptions apply.

Question 4Electrical Installation Standards (NFPA 70, National Electrical Code)

Which NEC article primarily covers the installation of optical fiber cables and raceways for low-voltage signal circuits?

  1. Article 800
  2. Article 760
  3. Article 770 Correct answer.
  4. Article 725

Explanation

Article 770 addresses optical fiber cables and raceways, including their installation, support, and separation from other systems. Article 725 covers Class 1, 2, and 3 circuits, Article 760 covers fire alarm systems, and Article 800 covers communications circuits.

Question 5Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage installer is supporting a run of Type CL3P cable. Which support requirement generally applies to this cable type?

  1. It must be supported at intervals not exceeding 12 inches.
  2. It must be supported at intervals not exceeding 4.5 feet. Correct answer.
  3. It must be supported at intervals not exceeding 10 feet.
  4. It must be supported at intervals not exceeding 25 feet.

Explanation

Class 3 cables such as CL3P are generally required to be supported at intervals not exceeding 4.5 feet (1.4 m). This spacing keeps the cable from sagging and limits strain on terminations.

Question 6Electrical Installation Standards (NFPA 70, National Electrical Code)

In a commercial building, a Class 2 cable is run through a plenum space above a suspended ceiling. Which cable marking is generally required?

  1. CL2R
  2. CL2
  3. CL2P Correct answer.
  4. CL2X

Explanation

Cables installed in plenums must be listed for plenum use, which is indicated by the P suffix, such as CL2P. The R suffix indicates riser use, X indicates limited use, and no suffix indicates general use. Plenum ratings are required because of fire and smoke concerns in air-handling spaces.

Question 7Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following best describes the purpose of the NEC's grounding requirements for low-voltage systems?

  1. To reduce the current-carrying capacity of conductors
  2. To eliminate the need for overcurrent protection
  3. To increase the operating voltage of the system
  4. To provide a low-impedance path for fault current and stabilize voltage Correct answer.

Explanation

Grounding provides a low-impedance return path for fault current so protective devices operate, and it stabilizes voltage to ground. It does not replace overcurrent protection or change conductor ampacity.

Question 8Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 power supply is listed as a Class 2 transformer with a 24-volt secondary. Which additional consideration applies to the secondary conductors?

  1. They may be any size because the circuit is power-limited.
  2. They must be sized to carry the secondary current without exceeding the ampacity of the conductors. Correct answer.
  3. They must be sized for the transformer primary current.
  4. They must be at least 12 AWG regardless of current.

Explanation

Even on power-limited circuits, conductors must be sized to carry the load current without exceeding their ampacity. The listing of the power supply limits the energy available but does not eliminate conductor sizing rules.

Question 9Electrical Installation Standards (NFPA 70, National Electrical Code)

Which NEC article covers fire alarm systems, including their power-limited circuits?

  1. Article 725
  2. Article 800
  3. Article 770
  4. Article 760 Correct answer.

Explanation

Article 760 covers fire alarm systems, including non-power-limited and power-limited fire alarm circuits. Article 725 covers general Class 1, 2, and 3 circuits, Article 770 covers optical fiber, and Article 800 covers communications circuits.

Question 10Electrical Installation Standards (NFPA 70, National Electrical Code)

When installing Class 2 cable in a raceway, which of the following is true regarding the raceway fill?

  1. The raceway may be filled to 100 percent because the circuit is power-limited.
  2. The raceway fill is governed only by the cable manufacturer's listing.
  3. The raceway fill must comply with the applicable chapter 3 or chapter 9 requirements. Correct answer.
  4. The raceway fill may exceed 40 percent if the cable is CL2P.

Explanation

Raceway fill for Class 2 cables must comply with the applicable NEC requirements, including Chapter 3 and Chapter 9 fill tables. Power-limited status does not exempt the installation from raceway fill limits.

Question 11Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is a characteristic of a Class 3 circuit compared with a Class 2 circuit?

  1. Class 3 circuits are limited to lower voltage than Class 2 circuits.
  2. Class 3 circuits must always be installed in rigid metal conduit.
  3. Class 3 circuits are not covered by Article 725.
  4. Class 3 circuits may carry higher energy levels than Class 2 circuits. Correct answer.

Explanation

Class 3 circuits are power-limited but are permitted higher voltage and energy limits than Class 2 circuits. Both are covered by Article 725, and neither requires rigid metal conduit universally.

Question 12Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage cable is installed in a hoistway. Which cable type is generally required?

  1. Any CL3 cable
  2. A cable listed for use in hoistways Correct answer.
  3. Any cable with a 300-volt rating
  4. Any CL2 cable

Explanation

Cables installed in hoistways must be specifically listed for that use because of the mechanical and fire hazards present. General-purpose Class 2 or Class 3 cable is not acceptable in a hoistway unless it carries the appropriate listing.

Question 13Electrical Installation Standards (NFPA 70, National Electrical Code)

What is the maximum voltage to ground for a Class 1 circuit in a low-voltage installation?

  1. 150 volts Correct answer.
  2. 30 volts
  3. 600 volts
  4. 1000 volts

Explanation

Class 1 circuits are generally limited to 600 volts between conductors, but the voltage to ground is limited to 150 volts for circuits supplied from a source other than a transformer. This distinguishes Class 1 from higher-voltage power circuits.

Question 14Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is the correct general rule for supporting Class 2 and Class 3 cables in a vertical raceway?

  1. They must be supported at the top and bottom only.
  2. They require no support in vertical raceways.
  3. They must be supported every 10 feet regardless of listing.
  4. They must be supported at intervals not exceeding the cable's listed support spacing. Correct answer.

Explanation

Cables in vertical raceways must be supported in accordance with their listing and the applicable NEC support requirements. The listing specifies the maximum support spacing, which may be more frequent than every 10 feet.

Question 15Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 circuit is installed in a building and the conductors are exposed. Which of the following is required?

  1. The conductors must be taped and stapled every 12 inches.
  2. The conductors must be enclosed in rigid metal conduit.
  3. The conductors must be installed in a raceway or be listed as a cable assembly. Correct answer.
  4. The conductors may be run as individual open conductors.

Explanation

Class 2 circuit conductors must be installed using a recognized wiring method, such as a raceway or a listed cable assembly. Bare individual conductors are not permitted as an exposed wiring method.

Question 16Electrical Installation Standards (NFPA 70, National Electrical Code)

Which NEC article addresses communications circuits, including their grounding and bonding?

  1. Article 800 Correct answer.
  2. Article 760
  3. Article 725
  4. Article 770

Explanation

Article 800 covers communications circuits, including requirements for grounding and bonding of communications systems. Article 725 covers Class 1, 2, and 3 circuits, Article 760 covers fire alarm, and Article 770 covers optical fiber.

Question 17Electrical Installation Standards (NFPA 70, National Electrical Code)

When Class 2 and Class 3 cables are installed in the same raceway, which condition must be met?

  1. They may never be mixed under any condition.
  2. They may be mixed freely because both are power-limited.
  3. They may be mixed only in metallic raceways.
  4. They may be mixed only if the Class 3 conductors are listed for the purpose. Correct answer.

Explanation

Class 2 and Class 3 conductors may occupy the same raceway only where the conductors are listed for the purpose or where a specific exception applies. The power-limited nature of both does not automatically permit mixing.

Question 18Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following best describes a listed Class 2 power source?

  1. A source that requires no overcurrent protection
  2. A source that is limited only by conductor size
  3. A source that has been evaluated to limit voltage and energy to Class 2 levels Correct answer.
  4. A source that supplies 120 volts to the load

Explanation

A listed Class 2 power source has been evaluated to ensure its output is limited to the voltage and energy levels permitted for Class 2 circuits. This listing is what allows the circuit to be treated as power-limited.

Question 19Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage installer is running CL2P cable through a fire-rated floor assembly. Which requirement applies?

  1. The cable must be supported every 12 inches.
  2. The penetration must be firestopped using an approved method. Correct answer.
  3. No firestopping is required for power-limited cable.
  4. The cable must be replaced with CL2X.

Explanation

Penetrations of fire-rated assemblies must be firestopped using an approved method, regardless of the circuit class. Power-limited status does not waive firestopping requirements.

Question 20Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is true about the ampacity of Class 2 circuit conductors?

  1. Ampacity is not a consideration for Class 2 circuits.
  2. Ampacity is determined solely by the power supply voltage.
  3. Ampacity must be adequate for the load and is based on the conductor's listing and installation conditions. Correct answer.
  4. Ampacity is always 15 amperes for Class 2 circuits.

Explanation

Class 2 conductors must have adequate ampacity for the load, determined by the conductor listing and the installation conditions. The power-limited source does not eliminate the need to consider ampacity.

Question 21Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is a permitted wiring method for Class 2 circuits in a building?

  1. Bare copper conductors
  2. Type AC cable used as a Class 2 conductor
  3. Type NM cable used as a Class 2 conductor
  4. Type CL2 cable Correct answer.

Explanation

Type CL2 cable is specifically listed for Class 2 circuits and is a recognized wiring method. Types NM and AC are power and lighting cables and are not used as Class 2 circuit conductors.

Question 22Electrical Installation Standards (NFPA 70, National Electrical Code)

In a low-voltage installation, which of the following is required for a Class 2 circuit that leaves the building?

  1. The circuit must be limited to 12 volts.
  2. The circuit must be protected by a listed primary protector. Correct answer.
  3. The circuit must be run in rigid metal conduit.
  4. The circuit must be grounded at both ends.

Explanation

Class 2 circuits that leave the building are generally required to be protected by a listed primary protector to limit surge and lightning exposure. This protection is separate from the Class 2 power supply listing.

Question 23Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following best describes the relationship between Article 725 and Article 300?

  1. Article 725 applies only to residential occupancies.
  2. Article 300 supersedes Article 725 entirely.
  3. Article 725 provides the circuit classification, while Article 300 provides general wiring method requirements. Correct answer.
  4. Article 300 applies only to high-voltage circuits.

Explanation

Article 725 classifies circuits and provides specific rules, while Article 300 provides general wiring method requirements that apply unless modified by the specific article. The two work together rather than one superseding the other.

Question 24Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 cable is installed parallel to a power circuit. Which separation requirement generally applies?

  1. The Class 2 cable must be installed in rigid metal conduit.
  2. No separation is required if the cable is CL2P.
  3. The power circuit must be de-energized during installation only.
  4. The Class 2 cable must be separated from the power circuit by a barrier or by spacing as required by the NEC. Correct answer.

Explanation

Class 2 cables must be separated from power conductors by a barrier or by the spacing required in the NEC to prevent inadvertent contact and induced voltage. Plenum rating does not eliminate the separation requirement.

Question 25Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is true about the marking of Class 2 cable?

  1. The cable must be marked with the circuit voltage only.
  2. The cable must be marked with the installation date.
  3. The cable must be marked only with the manufacturer's name.
  4. The cable must be marked with its class and, where applicable, its use rating such as P, R, or X. Correct answer.

Explanation

Class 2 cables must be marked with their class designation and, where applicable, the use rating suffix such as P for plenum, R for riser, or X for limited use. This marking allows the installer and inspector to verify suitability for the location.

Question 26Electrical Installation Standards (NFPA 70, National Electrical Code)

Under NEC Article 725, which condition defines a Class 2 remote-control circuit rather than a Class 3 circuit?

  1. The circuit uses conductors sized 14 AWG or larger for mechanical strength
  2. The circuit is powered directly from a branch circuit protected at 15 or 20 amperes
  3. The circuit operates at any voltage as long as the current is limited by an overcurrent device rated 20 amperes
  4. The circuit is supplied by a listed Class 2 power source and operates within the power and voltage limits set for Class 2 circuits Correct answer.

Explanation

Article 725 separates Class 2 and Class 3 circuits mainly by the energy they can deliver. A Class 2 circuit must be supplied from a listed Class 2 power source and stay within the power and voltage limits tabulated in Article 725. Class 3 circuits are permitted higher energy levels and therefore carry stricter wiring requirements.

Question 27Electrical Installation Standards (NFPA 70, National Electrical Code)

A technician installs a Class 2 cable that must pass through a plenum space used for environmental air. Which cable marking should be selected?

  1. CL2R
  2. CL2P Correct answer.
  3. CL2
  4. CL2X

Explanation

The suffix letters indicate the permitted use environment. The P suffix identifies cable listed for use in ducts, plenums, and other spaces used for environmental air. A plenum-rated Class 2 cable therefore carries the CL2P marking.

Question 28Electrical Installation Standards (NFPA 70, National Electrical Code)

What is the maximum branch-circuit overcurrent protection permitted for a Class 1 power-limited circuit?

  1. 15 amperes
  2. 30 amperes
  3. 60 amperes
  4. 20 amperes Correct answer.

Explanation

Article 725 treats a Class 1 power-limited circuit as one supplied through a listed power-limited source with branch-circuit overcurrent protection not exceeding 20 amperes. This limit is what keeps the available energy below the thresholds set for the power-limited category.

Question 29Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 cable must be run vertically between floors through a shaft. Which cable marking is the minimum riser designation for this application?

  1. CL2R Correct answer.
  2. CL2P
  3. CL2
  4. CL2X

Explanation

The R suffix designates cable listed for use in vertical runs in a shaft or riser. A Class 2 riser cable therefore bears the CL2R marking. CL2P is a permitted higher-rated substitute, but CL2R is the minimum riser designation among these choices.

Question 30Electrical Installation Standards (NFPA 70, National Electrical Code)

Which NEC article primarily governs the installation requirements for Class 2 and Class 3 remote-control, signaling, and power-limited circuits?

  1. Article 300
  2. Article 760
  3. Article 800
  4. Article 725 Correct answer.

Explanation

Article 725 is the dedicated article for Class 2 and Class 3 remote-control, signaling, and power-limited circuits. It establishes the circuit classifications and the wiring methods permitted for each. Class 1 circuit provisions are addressed separately in Article 724.

Question 31Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 circuit conductor is installed in a raceway with conductors of a 120-volt branch circuit. What does the NEC generally require for this arrangement?

  1. Mixing is permitted only if the branch circuit is protected at 15 amperes
  2. Mixing is always permitted because Class 2 conductors are insulated
  3. Mixing is permitted if the Class 2 conductors are color-coded orange
  4. The Class 2 conductors must be separated from the power conductors by a barrier or installed in a separate raceway unless specific reclassification conditions are met Correct answer.

Explanation

Class 2 and Class 3 conductors generally may not occupy the same raceway, enclosure, or cable with power conductors unless the low-voltage circuit is reclassified to Class 1 or another permitted condition is satisfied. A barrier or physical separation preserves the isolation that the low-energy classification depends on.

Question 32Electrical Installation Standards (NFPA 70, National Electrical Code)

How does the NEC generally treat the ampacity of Class 2 circuit conductors?

  1. Ampacity is not the controlling design factor because the listed Class 2 power source limits the available current Correct answer.
  2. Ampacity must be derated whenever the cable exceeds 10 feet
  3. Ampacity must be at least 20 amperes regardless of load
  4. Ampacity must be calculated using the same tables as branch-circuit conductors

Explanation

Because a Class 2 circuit is fed by a listed Class 2 power source, the source itself limits the current the conductors can carry. Ampacity calculations used for power wiring are therefore not the governing concern. The protection comes from the source characteristics rather than conductor sizing tables.

Question 33Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is a recognized wiring method for Class 2 circuits under Article 725?

  1. Only Type NM cable
  2. Only rigid metal conduit
  3. Type CL2 cable, power-limited tray cable, or conductors in a raceway Correct answer.
  4. Only open conductors supported on insulators

Explanation

Article 725 permits several wiring methods for Class 2 circuits, including listed Class 2 cable, power-limited tray cable, and conductors installed in raceways. The method chosen must also suit the environment, such as plenum or riser spaces. Restricting installation to a single method would be far more conservative than the code requires.

Question 34Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 cable runs through a floor assembly that has a fire-resistance rating. What is the general requirement for penetrating that assembly?

  1. No special protection is needed because Class 2 cable carries low energy
  2. The cable must be replaced with Type NM cable at the penetration
  3. The cable must be derated by 50 percent through the rated assembly
  4. The penetration must be firestopped using a listed method appropriate to the assembly Correct answer.

Explanation

Fire-rated assemblies must maintain their rating, so penetrations by cables of any class require an approved firestop system. The low energy of a Class 2 circuit does not exempt it from the building's fire-resistance requirements. Listed firestop methods are used to restore the assembly's integrity.

Question 35Electrical Installation Standards (NFPA 70, National Electrical Code)

When a Class 2 circuit leaves the building and runs outdoors between structures, what does the NEC generally require?

  1. The circuit must be protected by a 20-ampere overcurrent device
  2. The circuit may use any indoor cable because it is low voltage
  3. The circuit must be reclassified to Class 1
  4. The installation must comply with the applicable outside wiring provisions, such as Article 800 for communications or Article 820 for CATV, and use suitable cable Correct answer.

Explanation

Outdoor and between-building runs of low-voltage circuits are governed by the article specific to the system type, such as Article 800 for communications or Article 820 for community antenna systems. The cable must be suitable for the outdoor environment and installed per those provisions. Indoor-only cable is not acceptable for exposed exterior runs.

Question 36Electrical Installation Standards (NFPA 70, National Electrical Code)

Which statement best describes the relationship between Article 725 and Article 300?

  1. Article 300 governs all wiring methods, and Article 725 provides specific rules for Class 1, 2, and 3 circuits that supplement or modify those general requirements Correct answer.
  2. Article 725 and Article 300 never both apply to the same installation
  3. Article 300 applies only to voltages above 600 volts
  4. Article 725 replaces Article 300 entirely for low-voltage work

Explanation

Article 300 contains general requirements for wiring methods, and Article 725 adds specific rules for remote-control, signaling, and power-limited circuits. Where Article 725 provides a specific rule, it governs for those circuits, while the general provisions still apply where not modified. The two articles work together rather than excluding one another.

Question 37Electrical Installation Standards (NFPA 70, National Electrical Code)

What is the general separation requirement when Class 2 cable is run parallel to a power circuit in the same area?

  1. The cable must be installed in rigid metal conduit for its entire length
  2. The cable must be color-coded red
  3. The cable must be kept a minimum distance from the power conductors or separated by a barrier, in accordance with the applicable article Correct answer.
  4. No separation is required at any distance

Explanation

Class 2 cables are kept physically separated from power conductors to reduce the risk of energizing the low-voltage system and to limit electrical noise. Depending on the installation, this is achieved by maintaining a minimum spacing or by using a barrier. The specific distance or method comes from the governing article and the cable listing.

Question 38Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 1 circuit is not power-limited. Which wiring method is generally required for its conductors?

  1. Any Class 2 cable
  2. Type CL3P cable only
  3. The same wiring methods required for power and general wiring, such as raceway or approved cable Correct answer.
  4. Open conductors without support

Explanation

A non-power-limited Class 1 circuit can deliver energy comparable to power wiring, so it must use the wiring methods required for general power circuits. Class 2 and Class 3 cables are not acceptable for it. This is the practical consequence of exceeding the power-limited thresholds.

Question 39Electrical Installation Standards (NFPA 70, National Electrical Code)

What is the maximum voltage permitted for a Class 2 circuit?

  1. 150 volts
  2. 30 volts Correct answer.
  3. 300 volts
  4. 60 volts

Explanation

Class 2 circuits are limited to 30 volts under the Article 725 voltage thresholds, which is why they are commonly associated with low-voltage control and signaling. The limit applies along with the energy restrictions of the listed power source. Higher voltages move the circuit into Class 3 or Class 1 territory.

Question 40Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage installer is selecting cable for a Class 3 circuit in a plenum. Which marking should be used?

  1. CL3P Correct answer.
  2. CL2P
  3. CL3R
  4. CL3X

Explanation

Class 3 plenum cable is marked with CL3P, where CL3 identifies the class and P identifies plenum suitability. The class and environment designations must both match the installation. Using a Class 2 cable in a Class 3 circuit would not satisfy the class requirement.

Question 41Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is a permitted use of Class 3 cable in a building?

  1. Branch circuits feeding receptacles
  2. Fire pump power circuits
  3. Service entrance conductors
  4. Signaling and control circuits that exceed Class 2 energy limits but remain within Class 3 limits Correct answer.

Explanation

Class 3 circuits are signaling and control circuits that may carry more energy than Class 2 but stay within the Class 3 limits. Class 3 cable is intended for those circuits. Power, service, and fire pump circuits are governed by other articles and require power-rated wiring.

Question 42Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 cable is installed in a hoistway. Which consideration generally governs the cable selection?

  1. The cable must be derated to 50 percent of its marked ampacity
  2. The cable must be replaced with Type NM cable
  3. Any CL2 cable is acceptable because the circuit is low voltage
  4. The cable must be listed for the hoistway environment and comply with the applicable article for elevators Correct answer.

Explanation

Hoistways have specific environmental and fire considerations, so cable installed there must be listed for the application and comply with the elevator provisions of Article 620. General-purpose cable is not automatically acceptable just because the circuit is Class 2.

Question 43Electrical Installation Standards (NFPA 70, National Electrical Code)

What does the NEC require for supporting Class 2 and Class 3 cables installed horizontally?

  1. Cable must be supported every 100 feet
  2. No support is required for low-voltage cable
  3. Cable must be supported only at each end of the run
  4. Cable must be supported at intervals in accordance with the applicable article and the cable listing Correct answer.

Explanation

Article 725 requires Class 2 and Class 3 cables to be supported in a manner and at intervals consistent with the cable listing and the applicable installation provisions. Proper support prevents strain and damage. Leaving cable unsupported or supported only at the ends does not meet the requirement.

Question 44Electrical Installation Standards (NFPA 70, National Electrical Code)

A Class 2 circuit is exposed in a location subject to physical damage. What does the NEC generally require?

  1. The conductors must be protected by a raceway or other approved means suitable for the exposure Correct answer.
  2. The conductors must be painted to indicate low voltage
  3. Exposed Class 2 conductors are always permitted regardless of location
  4. The circuit must be converted to Class 3

Explanation

Where Class 2 conductors are exposed to physical damage, they must be protected by an approved means such as a raceway or suitable covering. The low energy of the circuit does not remove the need to protect the wiring from mechanical injury.

Question 45Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following best describes the grounding requirement for a Class 2 circuit?

  1. Class 2 circuits must never be grounded
  2. Class 2 circuits must be grounded at every outlet
  3. Class 2 circuits are generally not required to be grounded, but grounding and bonding may be required by the equipment listing or the applicable article Correct answer.
  4. Class 2 circuits must always be grounded at the source

Explanation

Because Class 2 circuits are energy-limited and isolated, they are generally not required to be grounded. However, the equipment listing or a specific article may call for grounding or bonding, so the installation instructions and the governing article must be checked. Absolute statements in either direction are incorrect.

Question 46Electrical Installation Standards (NFPA 70, National Electrical Code)

A technician needs to install a Class 2 circuit in a raceway with Class 3 conductors. What condition must be satisfied?

  1. Sharing is permitted if the Class 2 conductors are 18 AWG or larger
  2. The conductors may share a raceway if the Class 2 circuit is reclassified to Class 3 or the applicable article permits the combination Correct answer.
  3. Sharing is permitted if the raceway is metal
  4. Class 2 and Class 3 conductors may never share a raceway under any condition

Explanation

Class 2 and Class 3 conductors may share a raceway only where permitted by the applicable article, often by reclassifying the lower-class circuit to the higher class. The rule prevents a lower-energy circuit from being energized by a higher-energy one. Raceway material or conductor size alone does not authorize the combination.

Question 47Electrical Installation Standards (NFPA 70, National Electrical Code)

Which of the following is a characteristic of a Class 1 power-limited circuit compared with a non-power-limited Class 1 circuit?

  1. It is always installed with Class 2 cable
  2. It requires no overcurrent protection at all
  3. It may operate at any voltage without limit
  4. It is supplied by a source with a rated output of not more than 30 volts and 1000 volt-amperes Correct answer.

Explanation

A Class 1 power-limited circuit is supplied by a source with a rated output not exceeding 30 volts and 1000 volt-amperes. These output limits distinguish it from a non-power-limited Class 1 circuit. Source-specific overcurrent provisions apply; a universal 20-ampere branch-circuit limit does not define the classification.

Question 48Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage installer is routing CL2 cable through a suspended ceiling that is not used for environmental air. Which statement is correct?

  1. Only CL2X cable may be used above suspended ceilings
  2. Cable above a suspended ceiling must always be in rigid conduit
  3. A general-purpose CL2 cable may be acceptable where the space is not used for environmental air and the applicable article permits it Correct answer.
  4. Plenum-rated cable is required in every suspended ceiling

Explanation

Plenum ratings are triggered when the space is used for environmental air handling. In a ceiling cavity that is not a plenum, a general-purpose CL2 cable may be acceptable if the governing article and any local requirements allow it. The classification of the space, not the mere presence of a ceiling, determines the cable rating.

Question 49Electrical Installation Standards (NFPA 70, National Electrical Code)

Which statement correctly describes how the NEC treats a Class 2 circuit that is reclassified as a Class 1 circuit?

  1. The circuit may continue to use CL2X cable without restriction
  2. The circuit becomes exempt from Article 725 entirely
  3. The circuit keeps all Class 2 wiring privileges because the source is unchanged
  4. The circuit must then comply with the Class 1 installation requirements, including the applicable wiring methods Correct answer.

Explanation

When a circuit is reclassified to a higher class, it must meet the requirements that apply to that class, including the wiring methods for Class 1 circuits. Reclassification is a way to permit certain installations, but it comes with the stricter rules of the higher class. The original Class 2 privileges no longer apply.

Question 50Electrical Installation Standards (NFPA 70, National Electrical Code)

A low-voltage installer is choosing a cable for a Class 2 circuit that will be installed in a duct used to convey environmental air. Which cable marking is required for this location?

  1. CL2P Correct answer.
  2. CL2X
  3. CL2R
  4. CL2

Explanation

Cable installed in ducts or plenums used to convey environmental air must be listed for that purpose, and the NEC's class 2 cable markings use the suffix P for plenum-rated constructions. A cable marked CL2P is listed as suitable for use in ducts, plenums, and other space used for environmental air. Markings without the P suffix are intended for other locations, such as risers or general use.