Question 1

Knife switches rated more than ____, and at over 1000 amperes at 251 to 1000 volts, shall be used only as isolating switches and shall not be opened under load.

Accepted Answer

Knife switches rated more than 1200 amperes at 250 volts or less, and at over 1000 amperes at 251 to 1000 volts, shall be used only as isolating switches and shall not be opened under load. Therefore, option C is the correct answer.

Question 2

Means shall be provided to disconnect all conductors in a building (or other structure) from the ____.

Accepted Answer

Service-entrance conductors are the conductors that bring electrical power from the utility company's lines to the building's main electrical panel. Disconnecting these conductors will cut off power to the entire building, making it the safest option for maintenance or emergency situations.

Question 3

The combined length of one primary plus one secondary conductor (excluding any portion of the primary conductor protected at its ampacity) shall not exceed ____.

Accepted Answer

D

Question 4

Cable tray systems should be ____.

Accepted Answer

Cable tray systems should be corrosion resistant to prevent damage and degradation over time. Water tightness, insulation from frost damage, and mounting height above grade are not necessary considerations for the design of cable tray systems.

Question 5

Barriers are required in all service-entrance motor-control centers to ____ and terminals from the remainder of the motor-control center.

Accepted Answer

Barriers are used to isolate the service busbars and terminals from the other parts of the motor-control center. This is important for safety reasons and helps to prevent electrical shock or other hazards.

Question 6

A transformer's primary conductors shall have an ampacity at least ____ of the feeder conductors' overcurrent device rating.

Accepted Answer

The answer of A transformer's primary conductors shall have an...

Question 7

If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum, the supply-side bonding jumper shall have an area not less than ____ percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors.

Accepted Answer

The correct answer is 12.5 percent, as specified in the National Electrical Code (NEC) for determining the size of the supply-side bonding jumper when dealing with large conductors. This requirement ensures proper bonding and grounding for electrical safety.

Question 8

Cartridge fuse and fuseholder overcurrent protection provisions are located in ____.

Accepted Answer

Cartridge fuse and fuseholder overcurrent protection provisions are specifically covered in sections 240.60 and 240.61 of the National Electrical Code (NEC).

Question 9

A transformer vault door must be ____.

Accepted Answer

Equipping a transformer vault door with fully engaged locks ensures that only authorized personnel have access to the transformer, ensuring safety and security. While a door sill may be recommended for additional security, it is not specifically required for a transformer vault door. The door does not need to be accessible to all, as only authorized personnel should have access to the transformer. The type of material used to make the door is not specified, although it should meet industry safety standards.

Question 10

____ branch circuits shall be protected at the motor nameplate current rating.

Accepted Answer

Torque motor branch circuits are protected at the motor nameplate current rating, which ensures that the circuit is protected according to the specific current requirements of the motor itself.

Question 11

Overload is defined as operation of equipment in excess of normal, full-load rating, or of a conductor ____ that, when it persists for a sufficient length of time, would cause damage or dangerous overheating.

Accepted Answer

Overload is when the equipment is operated in excess of its rated ampacity.

Question 12

To calculate the ampacity of conductors supplying several motors (feeder conductors), multiply the largest motor full-load current (FLC) rating by ____% and add the FLC ratings of all other motors (or loads) in the group.

Accepted Answer

To calculate the ampacity of feeder conductors supplying several motors, you multiply the full-load current (FLC) rating of the largest motor by 125% and then add the FLC ratings of all other motors (or loads) in the group. This accounts for the largest motor's starting current, which is higher than its running current.

Question 13

Motor circuits rated 1000 volts, nominal, or less, shall have a disconnecting means with an ampere rating of at least ____% of the motor's full-load current rating.

Accepted Answer

According to the National Electrical Code (NEC), the disconnecting means for motor circuits rated 1000 volts, nominal, or less, must have an ampere rating of at least 115% of the motor's full-load current rating. This requirement ensures that the disconnect can handle the motor's normal operating current plus a margin for occasional overloads without tripping.

Question 14

Wherever such an arrangement is practicable, transformer vaults shall be located so that ____.

Accepted Answer

Ventilation to outside air should not rely on flues or ducts in order to avoid potential blockages and resulting safety hazards. The other options are not mentioned as necessary considerations for the location of transformer vaults.

Question 15

A tap conductor is a ____ that exceeds the value permitted for similar conductors protected as otherwise described in 240.4.

Accepted Answer

A tap conductor is a conductor that is connected to a primary conductor, and is used to supply power to a separate load, but is not considered a feeder. According to 240.21, tap conductors must have overcurrent protection ahead of their point of supply, and the rating of the protection must not exceed the ampacity of the tap conductor. If the tap conductor's ampacity is exceeded, it is considered a violation and requires correction. Therefore, answer A is the best choice because it correctly identifies the requirement for overcurrent protection on tap conductors.

Question 16

A ____ is the minimum size allowed if the overcurrent protection on the tap conductor's line side is 600 amperes.

Accepted Answer

The answer of A ____ is the minimum size allowed...

Question 17

The tap conductor's ampacity shall not be less than the ____ on the circuits it supplies.

Accepted Answer

The tap conductor's ampacity should be able to handle the combined calculated loads on the circuits it supplies, meaning the total amperage required by all connected loads. The other options do not accurately reflect the requirements for tap conductor ampacity.

Question 18

Where an orderly shutdown is required to minimize the personnel/equipment hazard(s), a system of coordination based on the following two conditions is permitted: (1) coordinated short-circuit protection and (2) ____.

Accepted Answer

The second condition for the system of coordination is overload indication based on monitoring systems or devices, as stated in the sentence. The other options (B, C, and D) are not mentioned as requirements for this system of coordination.

Question 19

If a single raceway supplies an equipment grounding conductor, only one ____ equipment grounding conductor is required.

Accepted Answer

According to NEC 250.122(F), if a single raceway supplies an equipment grounding conductor, only one equipment grounding conductor is required. The size of the equipment grounding conductor would depend on the size of the largest phase conductor in the raceway, but none of the options given are correct for this scenario.

Question 20

A 60-ampere rated conductor is the minimum size allowed if the overcurrent protection on the tap conductor's line side is ____.

Accepted Answer

The answer of A 60-ampere rated conductor is the minimum...

Quiz 17: Industrial Locations