Deck 3: General Requirements for Conductors

Question 1

​ ____ are used in conductor selection if the ambient temperature where the conductors are located is above or below 86 degrees F. ​

A)Overcurrent protectors
B)Rating factors
C)Maximum amperage factors
D)Correction factors

Answer 1

D

Question 2

​ Why is it important to place all conductors of the same circuit in the same raceway?

Answer 2

​ When all conductors of the same alternating-current circuit are in the same raceway, the magnetic flux around each conductor cancels out the magnetic flux of the other circuit conductors. If the flux does not cancel, induction heating of a metal raceway or metal-jacketed cable will occur. Also, if the conductors of a circuit were in different raceways, in the event of a fault, the impedance of the circuit would be higher than if all of the circuit conductors of the circuit were in the same raceway. This will lower the current flow and cause overcurrent devices to open more slowly, which is undesirable.

Question 3

Where would insulation with high-temperature rating be needed and why?

Answer 3

Boiler rooms, attics, and outside installations in the hot sun are examples of where the high-temperature rating might be needed. The big advantage of high-temperature insulations is they permit the use of the ampacity found in the 90 degrees C column of NEC Table 310.16  for applying adjustment and correction (derating)factors. In addition, some equipment may require conductor insulation rated higher than required for ampacity issues to safely withstand the temperature internal to the equipment.

Question 4

Which is an example of a continuous load?

A)store lighting
B)receptacle outlets
C)generators
D)overcurrent protection

Question 5

​ What is the purpose of conductor insulation with multiple ratings?

Question 6

For equipment rated at 100 amperes or less, the ampacity values found in the ____ column of NEC Table 310.16  are generally to be used.

A)60 degrees C
B)75 degrees C
C)90 degrees C
D)100 degrees C

Question 7

Dim or flickering lights may be caused by problems ____ if the voltage at the line-side terminals of the main service is satisfactory.

A)in the utility service
B)in the overcurrent protection
C)in the premises wiring
D)in the electrical grid

Question 8

Branch-circuit conductors are required to have an ampacity not less than ____ percent of the load to be served.

A)80
B)100
C)120
D)150

Question 9

Which factor does not generally influence the resistance of a conductor?

A)size
B)length
C)material
D)current

Question 10

The total voltage drop in the feeder and branch circuits should not exceed ____ percent.

A)2
B)3
C)5
D)10

Question 11

What is a typical example of thermoplastic insulation?

A)RHH
B)XHH
C)THWN
D)XHHW

Question 12

Adjustment factors must be used if more than ____ conductors are grouped together in a conduit or cable without maintaining spacing.

A)one
B)two
C)three
D)four

Question 13

What does AWG measure?

A)conductor size
B)conductor length
C)raceway length
D)ampacity

Question 14

Explain what is meant by wet locations with some examples.

Question 15

Several NEC sections contain the requirement to size conductors and overcurrent devices at 100 percent of the noncontinuous loads plus ____ percent of the continuous loads.

A)100
B)125
C)150
D)200

Question 16

​ What is thermoset insulation?