Code Standards and Practices Level 6 Practice Test

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• A motor switch listed as manual motor controller per UL 508 can be used as the motor branch-circuit disconnect.
• If loads are unnecessarily without power due to lack of selective coordination, the owner or management of the facility should be advised of the cause.
• A given automatic transfer switch (ATS) may have several SCCR levels that are marked by the manufacturer on the equipment, and the exterior marking must reflect the selected level.
• Under GFPE rules for feeder disconnects, when is a 1,000-amp feeder disconnect not required to have GFPE?
• GFPE is required for a 1,000-ampere service disconnect with 800-ampere fuses for a 480/277-volt, 3-phase, 4-wire, solidly grounded wye system.
• In the same scenario, what is the maximum secondary OCPD rating percentage?
• Zero sequence ground-fault protection monitors current in which conductors?
• Do ground-fault relays protect against high-magnitude ground faults?
• In the given example, the motor being described has a nameplate current rating of 23 amperes. What is the motor’s horsepower in that example?
• Which of the following statements about selective coordination status is true?
• Using the fuse manufacturer’s selective ratio tables, the needed ratio for selective coordination is 2:1. Which ampere combination may not selectively coordinate?
• What is the impedance percentage of the described 750-kVA transformer?
• Failing to implement selective coordination across an electrical distribution system can lead to what outcome?
• What is the main advantage of series-rated systems as described in the material?
• For transformers rated 1,000 volts or less, the secondary overcurrent protection devices can be up to how many in number?
• If the calculated secondary OCPD rating is not a standard ampere rating, what is permitted?
• For a new system installation, is it permissible to use a series rated combination even though there is no evidence the panelboard manufacturer has the panelboard listed and marked for the specific combination of OCPDs?
• Which rating must an MCC be marked with according to NEC requirements?
• End-use equipment for series-rated tested combinations must be labeled on which types of equipment?
• What is the stated intent of NEC 110.10 regarding short-circuit ratings, OCPDs, and circuit parameters?
• After selective coordination is installed, can an Electrical Worker inadvertently adjust a circuit breaker setting in a way that undermines coordination?
• What percent is used to adjust the full-load current to determine conductor ampacity for motor branch circuits?
• The transfer equipment’s exterior marking must reflect the SCCR level chosen for the installation, regardless of whether the OCPD is integral or line side.
• Adequate equipment SCCR ensures low arc flash risk assessment levels.
• For a 7% impedance transformer over 1,000 volts in a supervised location and without coordinated thermal overload protection, a primary fuse could be sized up to what percentage of the primary current without secondary protection?
• In a transformer sizing example, what multiplier is used on the primary full-load current to estimate the primary circuit breaker size?
• Which article covers the general installation requirements of transformers?
• What is the primary goal of short-circuit current ratings and selective coordination under fault conditions?
• The suitability of pull-out disconnecting switches with horsepower ratings is marked with which words?
• A series-rated system cannot be used where motors are connected on the load side of the higher-rated overcurrent device or on the line side of the lower-rated device, and where the sum of the motor full-load currents exceeds what percent of the interrupting rating of the lower-rated circuit breaker?
• What is the maximum time-delay permitted for ground-fault protection to operate on faults of 3,000 A or more?
• A mini-circuit breaker (UL 1077 supplemental protector) or supplemental fuses are suitable for motor branch-circuit short-circuit and ground-fault protection.
• There is a clear difference in reliability between complying with a 'selective coordination' requirement and a generic 'coordination' requirement, with the latter being less restrictive.
• Series-rated systems can cause problems with which of the following, according to the material?
• NEC, with a few exceptions, requires that air-conditioning and refrigeration, multi-motor, and combination-load equipment be marked with its SCCR.
• Which table is cited for the sizing values comparing circuit breakers to time-delay fuses in motor circuits?
• Is selective coordination mandatory for most electrical distribution systems?
• The motor-circuit protective device shall be capable of carrying the starting current of the motor. Which statement best reflects this requirement?
• For a 7.5 horsepower induction-type squirrel cage motor with nameplate current rating of 23 amperes operating at 3-phase, 208 volts, what is the full-load current used in calculations for motor branch-circuit conductor ampacity, short-circuit and ground-fault protective device ampere rating, and motor branch-circuit switch ampere rating?
• Is it safe to install an industrial control panel if its short-circuit current rating is less than the calculated available fault current at the installation point?
• Which protection provides protection from low-level, long-time overcurrent conditions which can overheat motors or motor branch-circuit components for 10 seconds or longer?
• UL 67 bulletin provides what content to accompany the panelboard?
• When installing new systems where selective coordination is mandatory, the Electrical Worker must install the proper type circuit breakers with the specified settings or the proper type/ampere rating fuses.
• Field marking of the SCCR on the exterior applies to which of the following transfer-related equipment?
• In GFPE residual sensor scheme, incorrect polarity of the neutral with respect to the associated phase conductors can cause what?
• Improper grounding of neutral conductors has no effect on the ability of a GFPE to detect ground fault currents accurately.
• When sizing the motor-compressor branch-circuit protective device, the rating or setting shall not exceed 175% of the motor-rated load current or branch-circuit selection current. If protection is not sufficient for starting current, the rating may be increased but shall not exceed what percent?
• In motor circuits with overload relays, circuit breakers may be sized up to what percent compared to time-delay fuses, and fuses may be sized up to what percent (or next standard ampere rating if values do not correspond)?
• Identify the NEC section where the following provision is located: A circuit breaker is used on a circuit having an available fault current higher than its marked interrupting rating by being connected on the load side of an acceptable overcurrent protective device having a higher rating. In this section, the circuit breaker shall meet the requirements specified in (A) or (B), and (C).
• Before installing an industrial control panel, what must be documented and what is the consequence if the marked SCCR is not equal to or greater than the available fault current?
• Circuit breaker manufacturers publish tables providing the range of overcurrents for which specific load-side molded case circuit breakers will selectively coordinate with specific line-side circuit breakers.
• Ground faults on large ampere services are always of the magnitude that the phase OCPD provides suitable protection against ground faults. Which statement best reflects this?
• Which service size is mentioned as an example when discussing ground fault protection capabilities?
• If the available fault currents exceed the selective coordination values shown for circuit-breaker-to-circuit-breaker pairs, selective coordination can be achieved.
• When a series-rated combination is selected under engineering supervision in existing installations, who is responsible for the selection?
• What is the required copper THW branch-circuit conductor size for a 3-phase, 75-horsepower, 240-volt motor with a nameplate current of 188 A and a 75°C terminal rating?
• The maximum circuit breaker rating as primary protection for a transformer of over 1,000 volts with an impedance of 3% in an unsupervised location would be calculated using what percent of the primary current?
• Before energizing any equipment, who should verify that the equipment SCCR is equal to or greater than the available fault current?
• Under NEC 430.37, how many phases must overload protection be provided for a 3-phase motor?
• A transformer supplying a fire pump is not permitted to have secondary overcurrent protection.
• NEC 700.5(F) requires the SCCR for emergency system transfer equipment to be field marked on the equipment's exterior.
• There are many requirements and limitations for series rated systems, but only one advantage: lower installed cost.
• For most systems, selective coordination is a design consideration but not mandatory; for some systems and circuits, selective coordination of the OCPDs is mandatory per the NEC.
• Ground-fault protection of equipment is not permitted for fire pump circuits or required for a continuous industrial process where a non-orderly shutdown would introduce additional hazards.
• The requirements for motor-circuit overcurrent protection for motors over 1,000 volts are covered in which section of Article 430?
• For a hermetic refrigerant motor-compressor, the rated load current marked on the nameplate is used in determining the rating or ampacity for which of the following?
• What is the minimum size copper THW conductor for branch-circuit conductors supplying a 10-horsepower, 230-volt, single-phase AC motor with terminals rated at 75°C?
• Determine the maximum primary fuse for installation in a 250-kva, 3-phase, 13.2- kv to 480/277-volt transformer with an impedance of 3.25% installed in an unsupervised location.
• For transformers exceeding 1,000 volts, are there different maximum ratings or settings of the overcurrent protection device for circuit breakers and fuses?
• Listed or labeled equipment must be installed and used in accordance with listing or labeling instructions. Which statement best describes this requirement?
• What term describes the maximum short-circuit current a piece of electrical equipment can safely withstand?
• Lower-magnitude ground faults may be detected by the main OCPD but would not be cleared promptly, potentially leading to damage. Is this statement true?
• In a real-world outage scenario, a 50 A branch-circuit breaker trips due to a short, but a 200 A feeder breaker supplying that branch also trips, causing a full process shutdown. This is an example of what?
• What should be done if an equipment SCCR is conditional on a specific type of OCPD and/or ampere rating?
• What is the maximum standard size rating of the motor branch-circuit short-circuit and ground-fault protective device for a 5-horsepower, 208-volt, 3-phase motor using time-delay fuses when starting current is not an issue?
• If the branch-circuit protective device value determined by NEC does not match a standard ampere rating, what is permitted?
• What type of service is specifically referenced for the voltage and grounding requirements of GFPE in the NEC context?
• Circuit breakers with short-time delay and no instantaneous trip can be equipped with an arc flash reduction maintenance switch to help mitigate incident energy during diagnostics on energized equipment.
• Is it permissible to use a series-rated combination in a new system installation if there is no evidence the panelboard manufacturer has the panelboard listed and marked for the specific OCPD combination?
• Code-Making Panels responsible for selective coordination state that this coordination will provide a more reliable system.
• What is the first step in the process for equipment SCCR design to installation?
• UL 67 allows for a bulletin or manual that lists all acceptable series rating combinations to be supplied with the panelboard.
• In the described transformer example, the ratio of primary to secondary voltage is approximately:
• Table 450.3(A) provides provisions for both 'any location' and 'supervised locations only.' True or False?
• Compared to non-selective coordination, selective coordination reduces cascading trips and improves reliability.
• Which table provides the full-load current values used for motor sizing in the example motor?
• Which description best matches a 3-wire 3-phase corner-grounded delta system?
• For continuous-duty motors with service factor 1.15 and more than 1 horsepower, must a separate motor overload device be used and rated at no more than 125 percent of the full-load current?
• +Large ampere rated service-entrance overcurrent protective devices may not always sense and open lower-level ground-fault conditions prior to extensive damage.
• A motor is located 100 feet from the motor control center that houses the motor branch-circuit disconnect. An instantaneous-trip circuit breaker can be used for the 'within-sight' motor disconnect. This would entail the instantaneous-trip circuit breaker being installed alone in a separate enclosure.
• In the 75-horsepower, 240-volt motor example, what is the full-load current used to size the branch conductors?
• If a system is not selectively coordinated, what is a likely consequence?
• The motor branch-circuit disconnect and the motor overload protection are typically:
• Motor controllers serve as the motor ON/OFF function.
• Selective coordination is achieved when OCPDs are chosen such that, on an overcurrent event, the nearest line-side OCPD opens to interrupt the fault and one or more upstream larger ampere-rated OCPDs open.
• What is Step 2 in the process from design to installation for equipment SCCR?
• For a wye-start, delta-run motor, the ampacity of conductors between the controller and the motor must be what percentage of the motor full-load current?
• Which NEC article covers interrupting rating requirements for equipment?
• A switch listed to UL 98 can be used as the motor branch-circuit disconnect.
• Which NEC section covers the motor disconnecting means?
• If the available fault current on an existing installation has increased beyond the circuit breaker’s interrupting rating, engineering methods may be used to determine whether series-rated combinations can be used.
• In a time-current curve, what does the horizontal axis represent?
• Which statement best describes the relationship between GFPE and protection during ground faults?
• For transformers rated at 1,000 volts or less, the secondary overcurrent protection device may be split into up to how many devices?
• Does NEC 408.6 require panelboards, switchboards, and switchgear to have a short-circuit current rating that is less than the available fault current?
• Secondary protection for a transformer rated 600 volts or less must comply with which sections, as described in the material?
• Which subsection specifies that tested series-rated combinations must be identified on end-use equipment, such as Panelboard and Switchboard?
• In healthcare facilities, does 517.17(B) require the feeders to have GFPE if the service has GFPE?
• Motor overcurrent protection is typically broken into motor and branch-circuit overload protection and what?
• A selective coordination approach is more restrictive and tends to provide a more reliable system.
• When splitting the secondary protection into multiple devices, which articles' conditions must be satisfied?
• A circuit breaker with which feature can delay tripping for a range of fault currents for a set period?
• Is it permissible to install equipment when its SCCR equals the calculated available fault current?
• Who must have access to the calculated available fault current documentation prior to installation?
• Where is the motor branch-circuit disconnect typically located in relation to the motor control center?
• GFPE stands for which term?
• As part of performance testing, a written record of the test must be available to the authority having jurisdiction.
• Section 110.15 requires legible field marking of equipment enclosures for series combination ratings in accordance with 240.86(A) and (B). True or false?
• SCCR stands for Short-Circuit Current Rating.
• For motor overload protection using fuses, a 3-wire 3-phase corner-grounded delta supply requires fuses in which conductors?
• The reliability of ground-fault protection can depend on not just the components, wiring, setting, and maintenance of the relay, but also what?
• Per UL 1077, supplementary protectors can be used for which motor circuit functions?
• For selective coordination with an upstream fuse of larger amperage, which must clear first?
• Which NEC section permits a horsepower-rated switch or circuit breaker to serve as both the motor controller and the disconnecting means?
• Residual ground-fault protection monitors ground fault currents in which conductor?
• Which of the following information must be marked on a motor controller?
• Which statement best describes the relationship between available fault current and line-side rating in a series-rated system?
• How many exceptions modify the scope statement of Article 450?
• In a 3-wire 3-phase corner-grounded delta system, how many conductors are considered grounded for protection purposes?
• For a 3-phase, 125-horsepower, 460-volt motor with terminals rated at 75°C, what is the minimum conductor ampacity and conductor size required?
• In a series-rated system, the line-side protective device can be in combination with a load-side circuit breaker. Which of the following describes the line-side device options?
• What is Step 3 in the process from design to installation for equipment marked with a short-circuit current rating?
• The ground-fault protection function requires opening which conductors of the faulted circuit?
• What is the maximum ground-fault protection setting (in amperes) for fault currents equal to or greater than 3,000 A?
• A fully rated system is defined as all overcurrent protection devices having an interrupting rating at least as great as the available fault current at their point of application.
• The effective time-current curve for ground-fault protection consists of the curve for the ground-fault relay and the phase overcurrent protective device.
• Which NEC requirement involves calculating the available fault current at the MCC location and documenting the calculation for the AHJ?
• For series-rated tested combinations, the end-use equipment must be tested, listed, and marked on which types of equipment?
• The primary fuses and circuit breakers can be sized at approximately 125%, or the next standard ampere rating, for the typical 480-volt to 208/120-volt, 15 kVA to 45 kVA dry-type transformers used in commercial installations because these transformers typically have low primary inrush currents. True or False?
• NEC selective coordination requirements primarily apply to loads vital for life safety, public safety, or national security, and panels claim it provides a more reliable system.
• The reliability of ground-fault protection can depend not only on the relay components, wiring, setting, and maintenance, but also on which of the following?
• The NEC 230.95(C) requirement for performance testing applies when GFPE is installed using which test method?
• Which statement about motor controllers is accurate?
• For a continuous-duty motor with service factor 1.15 and more than one horsepower, the separate motor overload device must trip or be rated at no more than what percent of the motor nameplate full-load current rating?
• Mini-circuit breakers (UL 1077 supplemental protectors) are suitable for motor branch-circuit short-circuit and ground-fault protection.
• An adequate OCPD interrupting rating ensures that load-side electrical equipment will be provided with adequate short-circuit protection.
• If the primary full-load current is 104.21 A, the calculated primary circuit breaker size (104.21 A × 6.0) is approximately which amperage?
• Does Code Section 230.95 require GFPE on a 1,000-ampere service disconnect for a 208/120-volt, solidly grounded system?
• Where must the SCCR be marked on equipment that is used to indicate its short-circuit performance?
• Selective coordination is required for multiple elevators supplied by the same source.
• For a transformer with primary and secondary ratings of nine amperes or more and no coordinated thermal overload protection, what combination of primary and secondary OCPD percentages is required?
• Which statement about who completes the selection of overcurrent protective devices for selective coordination is incorrect?
• If selective coordination is required or important, it is important to select the appropriate types of OCPDs and ampere ratings/settings in the design phase.
• What factor multiplier is used to determine the maximum time-delay fuse size from full-load current?
• In analyzing circuit breakers in their instantaneous region, which times must be considered to determine selective coordination?
• For a 7.5-horsepower, 3-phase, 208-volt induction motor, what is the full-load current used for calculations?
• The intent of which NEC section is that the equipment SCCR, OCPDs, and circuit parameters must be selected and coordinated to limit damage under short-circuit conditions?
• For a wye-start, delta-run connected motor, the line-side conductors on the controller side shall be based on what percentage of motor full-load current, and the conductors between the controller and the motor on what percentage?
• Electrical equipment is required to be adequately protected against short-circuit conditions per NEC and OSHA.
• Is it true that the maximum rating or setting of overcurrent protection for transformers under 1,000 volts per 450.3 is different for circuit breakers compared to fuses?
• Which statement about SCCR is correct?
• A component such as a power distribution block can have a marked high short-circuit current rating greater than 10,000 amperes when protected by marked specific type and ampere rating overcurrent protective devices.
• Since 1971 edition NEC, 3-phase motors only need two phases protected with properly sized overload protection.
• Which of the following is not a motor branch circuit major functional block?
• According to Table 450.3(B), for a three-phase transformer with primary and secondary ratings of nine amperes or more and with no coordinated thermal overload protection, the maximum primary OCPD rating is what percentage of the transformer rating?
• A 20-ampere circuit breaker with an interrupting rating of 10,000 amperes can be installed at a point with available fault current of 65,000 amperes only if it is series rated with a lineside device that has a series rating of at least what value?
• Primary inrush current characteristics can vary by transformer design. True or False?
• Motor branch-circuit short-circuit and ground-fault protection and motor overload protection shall be permitted to be combined in a single protective device when the device rating or setting provides the overload protection specified in 430.32.
• In a series-rated arrangement, the available fault current at the line side must be greater than the load-side interrupting rating but not greater than the rating of which device?
• An OCPD specified to help an apparatus achieve an SCCR may be integral to the apparatus or located on the line side.
• NEC 700.32 requires each emergency system OCPD to selectively coordinate with all supply-side and load-side OCPDs.
• A disconnecting means 'in sight from the motor' is intended and used only as an emergency disconnecting means.
• A fault of a circuit that is not selectively coordinated can result in an event commonly referred to in the industry as what?
• Secondary protection is typically required for a 3-phase transformer rated 600 volts or less to comply with which sections?
• When a group of not more than 6 overcurrent devices is used as the transformer’s secondary protection (1000 volts, nominal or less), the sum of all device ratings shall not exceed what value?
• Series-rated protection can hinder which of the following aspects of a power distribution system?
• In the example, the motor described is connected as a 3-phase machine at what primary voltage level?
• The described supply system type is best classified as which of the following?
• What does the acronym OCPD stand for in electrical protection terminology?
• What is the marked service factor used in the 75-horsepower motor example?
• Ground-fault protection of equipment shall be provided for solidly grounded wye electric services of more than 150 volts to ground, but not exceeding 1,000 volts phase-to-phase, for each service disconnect rated 1,000 amperes or more.
• Which method of GFPE protection is considered to provide less effective protection if there are any inadvertent connections between ground and neutral downstream of the grounding strap?
• Which table provides the percentages for the transformer OCPD sizing discussed?
• The performance test shall be conducted in accordance with instructions that are required to be provided with the GFPE equipment.
• Which of the following is a reason Electrical Workers should understand selective coordination?
• What is the impedance percentage of the transformer in the 250-kVA example?
• The ground-fault protection system shall be performance tested when first installed on site. Which elements are required as part of this performance testing?
• What temperature rise is specified for the 75-horsepower motor example?
• What is the maximum overload protection trip rating for a 3-phase, 75-horsepower, 240-volt motor with a nameplate current of 188 A and a service factor of 1.15 when starting current is not a problem?
• If an industrial control panel is to be marked with its SCCR by the panel builder, the available fault current must be determined and the date it was performed must be available to the inspector or the AHJ.
• A component can have a high SCCR (greater than 10,000 A) when protected by a specific type and ampere rating overcurrent protective devices.
• What is the maximum standard fuse size for a 3-phase, 75-horsepower, 240-volt motor with a full-load current of 192 A, using time-delay dual-element fuses (next higher standard rating allowed)?
• A 3-phase, 750-kVA, 5.75% impedance transformer in an unsupervised location, with a primary voltage of 4,160 volts and a secondary voltage of 480 volts, could have a primary circuit breaker sized at a maximum of how many amperes?
• What term describes a system intended to protect equipment from damaging line-to-ground fault currents by opening all ungrounded conductors of the faulted circuit?
• Which NEC sections require legible field marking of equipment enclosures for circuit breakers or fuses applied in compliance with series combination ratings?